Tristan Lougher explains why it pays to be prepared before stocking the tricky Powder blue surgeonfish.
Common name: Powder blue tang (surgeonfish).
Scientific name: Acanthurus leucosternon (Ack-ann-thur-uss loo-co-stern-on).
Size: To 23cm/9in.
Origin/natural habitat: Reef flats of the Indian Ocean from the east coast of Africa to Indonesia. Reported also from Bali in the Western Pacific.
Tank size: 400 l/88 gal plus.
Water chemistry: Ammonia and nitrite should be zero. Stable pH 8.1-8.4 is advised. Nitrate should be below 25ppm, ideally lower.
Approximate lifespan: Five years plus. Specimens kept well should live into double figures.
Sexing: External sexual differences have been reported such as nuances in body shape and pattern, but these are not discernible in any but the largest most mature fish where females are substantially larger than males.
Spontaneous purchases of marine fish can work but often don’t. There are so many species to choose from already, and there are several new-to-the-hobby species being imported every year. So, it’s perhaps unsurprising that aquarists can encounter fish they have never seen before in their dealer’s aquaria.
However, there are many fish that are instantly recognisable and about which there is an abundance of information.
Popular because of their ravishing good looks, affordability and widespread availability, one might be forgiven for thinking that they are easy to keep too. While by no means impossible, they can present unprepared aquarists with serious problems. However, a little background research and planning means that an aquarium can be established that provides for the specific needs of these fish in the long-term.
The Powder blue surgeonfish is many things: iconic, beautiful and yet potentially frustrating when it proves difficult to keep. Establishing an aquarium that addresses its particular needs and potential problems from the moment of its conception through to design, construction, then finally stocking is a way of avoiding many of the potential problems with this beautiful surgeonfish. Of course, most Powder blues do not have their entire system designed around them and they can still thrive in mixed systems. However, many aquarists have learned the hard way not to impulse buy one. Most of the key points that help aquarists to achieve success with this species are applicable to any aquarium, but for those wanting to recreate a little slice of nature, the reef flat aquarium is a great place to start.
In common with many surgeonfish, the Powder blue surgeonfish will fiercely defend areas of macroalgae from competitors or indeed any fish it perceives as a threat. In its natural environment, it may have to see off marauding shoals of the rival surgeonfish such as the Convict surgeon, Acanthurus triostegus, with aggressive attacking use of the scalpel-like scales located on its caudal peduncle. Although large shoals numbering hundreds of Powder blue individuals are also seen with regularity, it is generally intolerant of members of its own species and, at the margins of their territories, pairs will display and skirmish with rivals.
Its laterally compressed body shape and low-slung mouth are ideal for getting into nooks and crannies to remove algae, and it will busily swim throughout its territory searching for food. Here it might form loose associations with other species of surgeonfish including members of the genus Ctenochaetus, the bristletooth tangs. It has been suggested that this form of tolerance of similar species is convenient to each, as it increases the chances of new browsing sites being found and also offers some safety in numbers from predators.
Stop problems before they start
Researching potential issues with fish before establishing an aquarium for them allows the aquarist to manage problems before they occur. Aquarists that aspire to maintain the powder blue in the short, medium and long-term must address and solve each of these problems through system design and careful selection.
1. Their tendency to invite disease when stocked into their new home. They invariably contract Cryptocaryon (marine white spot) between two and ten days after being introduced.
2. Specimen selection: Is it feeding? Is it healthy? Of course, these types of questions can and should be asked of any fish before purchase, but for some marine species, identifying those individuals that are bold and greedy in their feeding behaviour can make their transition to the home aquarium an even smoother one.
3. Their territorial nature: many marine fish are territorially aggressive and the Powder blue isn’t the worst of them. It isn’t even the worst surgeonfish, but the same instincts that drive it to defend it’s patch of alga from raiders can kick in in the home aquarium, and in a closed system this can lead to serious injuries being sustained by its tank mates.
Buy better fish
Although research and planning are essential when selecting fish species for inclusion in a saltwater aquarium, it is vitally important that decisions concerning the actual specimen to be stocked into your aquarium are based on the individual rather than the species. Hopefully, you will already have determined whether the species itself is suitable for your particular aquarium, and that includes both hardware and species stocked/to be stocked.
Try to see a number of Powder blue specimens before you buy one. How do they compare with specimens you saw during your research? How do they compare with wild photographed fish? This should help give you a feel for the species, how it looks in a dealer’s aquarium and some understanding of what to look out for in the individual you end up buying. It is also useful to decide whether a smaller or larger individual is better stocked in your particular circumstance, and that might be influenced by the size and disposition of the other fish to be stocked.
When it comes to the time to buy, ensure that you see it feeding before you commit to the purchase. Ideally, it should browse on algae (dried and/or natural forms) in addition to meaty offerings such as Brine shrimp or Mysis.
Avoid individuals where the spine is visible; it’s possible to reverse the weight loss incurred when fish are collected and shipped and this is likely to occur when fish are fed sufficiently well on quality foodstuffs. However, this is a variable that the new Powder blue owner doesn’t need, and having high standards during the selection process should increase the chances of success.
Occasionally, specimens that are feeding well on flake and pellet diets can be found, and those are likely to be the best settled. Ask how long an individual has been in residence at the dealer’s; the better individuals are likely to have been in stock for a number of days or weeks.
How do we define 'better'? It’s not all about colour although that too can be an indication of health and vitality. Sometimes fish held in intensive marine fish-only systems can lose a little colour over time. The good news is that if the aquarist prioritises the fact that they are feeding well and have recovered from shipping over vibrancy of colour then the intensity and beauty of their colours should be regained within a matter of days in most instances.
Add tank mates first
The benefit of the creation of an aquarium that provides for the needs of fish that can be classed as 'tricky', is that more straightforward species will usually benefit from the extra planning and enhancements to the system. For example, surgeonfish are not the only species to suffer from white spot infections and therefore inclusion of a UV benefits all newly introduced fish. Establishing the aquarium to be sympathetic to the fish’s natural environment could even inspire the aquarist to pursue the biotope aquarium where the sunlit reef flat fauna is recreated to an extent.
The good news is that the Powder blue will live with almost any tank mates given sufficient time to settle in a new home, but its territoriality can be an issue. The willingness to form schools with other, similar algae-grazing species in the wild is not something to be attempted lightly in the aquarium. Indeed, it can be best avoided altogether. Their intolerance of competitors for algae might be understandable, but less easily explained is their apparent hatred of butterflyfish. None of these blends of fish groups are impossible to recreate in the home aquarium but perhaps best avoided in a system where the well-being of the Powder blue is a priority.
Bear in mind that the territorial nature of this surgeonfish is likely to be enhanced by the aquarist offering meagre rations; an approach often adopted by aquarists who understandably want to prioritise their water quality. One of the best ways to avoid conflict is to make this the final large-fish addition to the aquarium, i.e. after all of the other species have been given a chance to settle over a number of weeks. This might not eliminate territoriality entirely, but it should reduce it. That, together with some suitable choices for tank mates can make all the difference.
Another possible solution to the stocking of territorial species is to stock all potentially aggressive species simultaneously and as small juveniles. In the case of most surgeonfish and tangs, which may compete for natural algae resources in the aquarium, there may be limits regarding just how small the specimens available to be stocked are. At least adding them at the same time means that they are all in the position of having been stressed while being moved to their new aquarium and will settle in at similar rates.
This is particularly useful when stocking surgeonfish that are even more territorially aggressive than the Powder blue: surgeonfish such as the Red Sea’s Sohal, Acanthurus sohal, and the Indo-Pacific’s Clown, A. lineatus.
Smaller, busy fish such as anthias (Pseudanthias spp.), damselfish (Pomacentridae), dottybacks (Pseudochromis spp.), fairy wrasse (Cirrhilabrus spp.), peacock wrasse (Macropharyngodon spp.) and flasher wrasse (Paracheilinus spp.) are all suitable groups with which Powder blues will mix with the minimum of conflict. Stock larger fish such as dwarf angelfish, larger wrasse and angelfish before the Powder blue. Of course, any species choices will also be influenced by the variety of sessile invertebrates, if any, that are also stocked.
For the majority of specimens, once the first month in their new home has been successfully negotiated, they will go from strength to strength. However, water quality must be maintained to high standards and care must be given to the diet of the surgeonfish. Given that the Powder blue is one of the last fish stocked into the system, at least the last fish of any size that should be stocked, attention will have to be given to feeding all of the other fish in the aquarium too and to ensure that they are not competing too strongly with
the Powder blue.
One of the best ways to offer food to this fish is using nori or other forms of dried alga (dried sushi nori is the form I find most Powder blues accept most readily) on a seaweed clip daily. This should ideally be placed into the aquarium in the morning (or when the daylight period of the aquarium begins), so the fish can browse throughout the day. Meatier offerings can be made; pellets and flake are often accepted by this species, as are familiar frozen diets such as
Mysis and Brine shrimp. There are many other formulations of frozen food containing algal enrichments or high percentages of vegetable material that are also suitable. Keep the diet varied and of high quality, but always offer the dried alga.
How to set up a Powder blue surgeonfish tank
Tank size: 400 l/88 gal is an absolute minimum for this species long-term. It will afford swimming space for this active fish and a water volume that is sufficiently large to afford some stability to the system.
Filtration: For me, the best way to create an aquarium sympathetic to the needs of a Powder blue is to make it a living rock based system. This means the bacteria within the rock itself will provide the biological filtration: the removal of ammonia and nitrite.
Nitrate can be controlled to an extent by other varieties of live rock based bacteria and enhanced through the use of carbon dosing, whether with liquid alcohol based products or through the use of bio-pellet reactors. A good-sized, efficient protein skimmer is essential whether carbon dosing is employed or not.
Water currents and their intensity will be determined by the species of coral where stocked, but Powder blues do seem to enjoy areas of vigorous water movement provided by stream-type pumps, as long as they have areas where they can find quieter water.
Equipment: You are going to need an ultraviolet (UV) steriliser. You might be one of the lucky people who stock a Powder blue that never develops a protozoan parasite such as white spot (Cryptocaryon) or marine velvet (Amyloodinium), but that would place you in the minority of aquarists with experience of this species.
Thinking you might get lucky is a big mistake, and why endanger the life of not only your Powder blue, but also the rest of your stock, as the aforementioned parasites are highly contagious and potentially lethal. This, coupled with the fact that treatment options in a reef aquarium containing live rock and corals are extremely limited and it becomes clear that the UV cannot be seen as an option; it’s compulsory. Prevention is always better than cure in these situations, and running the UV when the fish is introduced to the system and for a period of three to four weeks subsequently will increase your chances of success with this fish.
If you plan on keeping corals in the Powder blue aquarium, and there is no reason why you shouldn’t, then the lighting will need to be adequate for the species/varieties chosen. LED illumination gives that authentic rippling light effect that is such a prominent part of the shallow reef experience. Although the current trend for high percentages of blue light in stony coral aquariums enhances the fluorescent proteins in their tissues, lower Kelvin ratings will afford a whiter light that will showcase the fabulous colouration of the Powder blue as well as faithfully recreate the shallow water in which this fish is commonly encountered.
Aquascaping: Powder blue surgeonfish adore swimming space. In this system, building a shallow incline of reef at about 30 degrees to the horizontal affords plenty of open water and yet still lots of rocky substrate over which the fish can browse for algae. Alternatively, you could opt for a horizontal arrangement of rock with one or two sand or rubble patches that would recreate the reef
flat zone nicely. Corals can be widely spaced giving focal points of interest with plenty of exposed rock over which the fish can browse.
Quarantining is a hard process to argue against for any fish, saltwater or freshwater, but reality dictates that few marine aquarists have the budget and space to establish a system into which fish can be placed, observed and treated and therefore don’t own one. Lack of quarantining is another one of the reasons why a UV steriliser is an essential piece of kit for the Powder blue.
Most fishkeepers consider keeping Zebra plecs and many would like to breed them. But whatever your goal, you'll need to know to look after them, says Julian Dignall.
The only thing black and white about the Zebra plec is its beautiful markings. Pretty much everything else is subject to myth, opinion and misinformation.
This, as well as the beautifully contrasting stripes, do add to the somewhat legendary status the Zebra plec, Hypancistrus zebra,
Depending on whom you speak to, the Zebra plec was discovered by anglers somewhere between the mid 1970s and 80s. It was given an L-number, L046, in 1989. The stripes of the Zebra have come to represent a new wave of catfish keepers, and it’s a flagship species for the now undeniable fishkeeping tribe that are L-number keepers and breeders.
The Zebra plec is endemic to the middle of Brazil’s Rio Xingu (pronounced sheen goo) and is among the catfish species at risk from the Belo Monte dam.
It lives at a depth where the surroundings are, at best, pretty gloomy, if not completely dark. It lives in the cracks, gaps and natural caves found in the very specific type of rock found in the river.
This is dark brown to black hard igneous rock that, in shallower water, is set in tan-coloured sand. There is very little submerged wood, there are virtually no plants and the water belts through the area at a rate of knots. Many of these areas are rapids and the water is highly oxygenated.
Exports of tropical fish from Brazil are governed and policed by the Brazilian Institute of Environment and Renewable Natural Resources (IBAMA). IBAMA produces a so-called positive list of fish species and those are the ones that may be collected and exported into the global ornamental fish trade. Hypancistrus zebra has not yet appeared on it and is illegal to export from Brazil.
When you encounter one for sale it will either be captive-bred or will have been smuggled out of Brazil and exported, typically, from Colombia. They range from around £95-£150. This activity, as you may imagine, stirs some debate among fishkeepers. Even if such a wonderful species is at risk of extinction in the wild, does that make it acceptable to fund the smuggling of them into our shops? That’s to say, 'rescue' them before they are wiped out.
Thankfully, the Zebra plec’s future looks a bit brighter than many of its Xingu river cohorts. Because of its small size, relative ease of breeding and status, it is bred and traded in most countries that have a decent aquarium hobby.
In the aquarium
Keeping Hypancistrus zebra is straightforward, especially with captive-bred stock. When this species was first being bred in aquaria, arguments raged over how to best keep and breed it. Some polarised views were initially stated, but it turns out most folks were right, even if they had different points of view, because this species can live in a range of water conditions.
So, the hard water proponent was no more right or wrong than their softer water advocate. It has been bred in really quite hard water with no ill effects, though most spawns are in about pH 6.5-7 with moderate to no hardness.
I accept that breeding fish isn’t everyone’s cup of tea. It’s not a view I subscribe to personally, but I get the fact that people just want to look at their fish rather than reproduce them. However, in the case of the Zebra plec the majority do wish to breed them.
This may be for any mix of anticipated financial gain, fishkeeping kudos or the positive feeling gained from furthering the chances of this species’ ability to survive for future generations. So, let’s talk about how to keep them so that they breed and then, if you remain convinced you don’t want to breed them, you still have the intel on how best to keep them
Provide warm, oxygenated and clean water. Aim for a neutral pH, a water temperature of 86-88°F/30-31°C and have at least two power-driven filter outlets that mix in atmospheric air with the water flow. Clean water means both a decent power filter and at least 25% water changes.
Consider using plants and bogwood to replicate the natural habitat.
Feed them right
Feeding is more a matter of physics than biology. Zebras are not large plecs and you can keep a group in a relatively small tank. However, with all that filtration in play (see box above, right) food can get blasted around the tank and filtered away before the fish get to eat.
This is where some trial and error with aquascaping comes in. Play around with rocks so that there are some open areas of gravel where food collects. Even better would be near caves. If you can, do this in such a way as it’s easily accessible.
It may sound obvious, but be really careful moving rocks around with plecs in the tank. It is easy to trap or squash them, especially if you are stretching or off balance.
Aim for an aquarium that allows food to sink to quiet pockets away from the current, where the plecs can feed over a ten to 15 minute period once or twice a day. The choice of food is important. Flake or floating foods won’t do well in that kind of current, so sinking tablets made from flake or algae tabs will work, but Zebras need a lot of protein. I favour discus food, either frozen or granular. Select one that doesn’t expand a lot once placed in water. Many plecs will gorge on whatever food is available and something that expands to twice its size after being submerged for five minutes is remarkably lethal. This is especially true in plecs, as two thirds of their bodies are covered by rigid plates, so the only way the stomach can expand is downwards where there is only exposed skin.
Keep discus separate
The temptation to keep Zebras with discus is strong, as they share water requirements and similar diets. But the issue of water current can be overlooked. If you’ve got a filter that provides lots of dissolved oxygen (but without the kind of current that would scatter the discus around the tank), then this might work but it’s a bit hit or miss.
If you’ve a central system, then keeping Zebras in one tank and discus in another in the same system would work well, as you can add a pump/filter to the Zebra tank to create the extra current, but I’d suggest keeping these two fish apart in the main.
I like to keep plecs in oversized tanks because it means I have a lot more flexibility when it comes to looking after their water. For example, I have a group of five Zebra plecs breeding in a tank that has a 91 x 46cm/36 x 18" footprint and is 38cm/15" high.
In this is 2mm bore gravel to a depth of about 1". I mix black and brown gravel to get a look that I like and it appears the Zebras are, at least, not objectionable to. The black and white fish look fantastic against what is not only attractive, but reasonably natural substrate. On top of this, I have lots of breeding cave pipes and then slate and lateritic holey rock.
Zebra plecs won’t breed unless caves are present. These are commercially available or you can make your own. As a rule of thumb, I put two caves in for every adult fish. This is seen by some as overkill: some authors have one cave. However, I note a lot of aggression over caves and the alpha male will always pick the one that suits him best. So, if there are others available, the fighting is toned down a bit and, like me, you might be lucky and get two pairs spawning. This is relatively unusual, and it’s more common for males to breed with more than one female, a few weeks apart, but in the same cave. Females will live near the male’s cave, and so I like to provide rock cover over the caves that are thus in shade.
The temptation is to have them in full view so you can monitor proceedings, but it’s more important to have the cave mouth perpendicular to the current and for all the adult fish in the tank to be able to come and go from their places of rest without too much aggro.
Get the décor wrong and adult male Hypancistrus can seriously injure and kill each other. However, many people buy captive-bred Zebra plecs and they tend to be a bit smaller and not yet mature. Thus, such aggression has yet to manifest itself and can be avoided altogether by adding refuges as the fish begin to mature.
Sexing your zebra plecs
In well-conditioned, mature fish, sexing is straightforward. Applying these observations to fish less than about 80mm SL or that have not been in captivity for long will give variable results.
1. Full-grown male Zebro plecs are about 10-15% larger and bulkier than females.
2. The male’s interopercular odontodes that have grown from the fish’s cheek under the eye are longer — more than two times the width of the eye.
3. The male’s leading pectoral fin spine has orange-tipped odontodal growth of a similar thickness, if not length, to the cheek spines.
4. Males have heavy-set heads.
5. When viewed from above, males have a straight line from the base of the pectoral fin spine to the caudal peduncle.
6. Flip them over and examine their pinky-white undersides: males have pointier bullet-shaped genital papillae.
7. Females are generally slighter.
8. While females develop cheek and pectoral fin spines with maturity, they are shorter and less noticeable than the males’.
9. Females have a convex, curved outline from the base of their pectoral fin spine to the caudal peduncle (broadest in the midriff where eggs will be developed).
10. Underneath, females have a much less defined, but broadened genital papillae.
Much debate surrounds spawning triggers. Some authors report that not cleaning the filter — therefore slowing the water current a little — along with skipping a water change or two followed by increased water changes triggers well-conditioned pairs to spawn. Many say they will start spawning when mature given good water conditions. Certainly once they do start they will continue for years.
Often the first batch of yellowish orange eggs will be infertile and not hatch. This commonly happens with many plec first timers. It’s just a sign to keep doing what you’ve been doing — within a month, they will try again, maybe sooner.
The male will normally guard the eggs in the cave and often the first an aquarist knows they’ve bred is on seeing some delightful mini Zebras scooting around the tank, typically under stones.
If disturbed or inexperienced, the male may displace the eggs out from the cave. In this situation, or where you want to micro manage the eggs hatching, then an in-tank nursery is required. This can be a net mesh box or a more sophisticated plastic box, but the important things are that it shares water from the parent tank and is easy to clean. Place an airstone close to the egg clutch to simulate the fanning of the male’s fins in the cave.
When they hatch, youngsters will have unfeasibly large yolk sacs. It is only when these are consumed that you should start feeding. Crush whatever you’re feeding the adults and consider sinking tablets too. They are not hard to feed and even at this small size will eat dry foods eagerly and regularly. For best results try to feed twice a day or more. Clean the nursery at least daily, it needs to sparkle.
However, I prefer the hands-on dad approach and Zebra plec dads do a great job of getting 20 or so youngsters out of the cave. At this size they will forage and eat with the adults. They’re slow growers and unless you pay them a lot of attention in terms of feeding, space and water quality, getting them to grow more than 1cm every 6-8 weeks will be a challenge.
Zebra plecs are now bred in commercial numbers and these turn out beautiful clean fish in number. Also, shipments of wild-caught fish tend to have more males than females (it’s easier to collect males from the wild as they tend to be in a cave), but with captive-bred fish, it is more like parity. Because these are high-end fish, professional breeders know they must be kept in high quality surroundings to ensure they grow on well and fast.
Zebra plecs produce about 20 eggs and spawn every couple of months. These figures can be improved a little with ultra-attentive care but serve as a good indication. So, one pair could produce about 120 offspring a year. Let’s call that 100 once you take into account culling of inferior fish and the odd accidental loss for whatever reason. Now you need another year to bring them on. That’s running, say, eight tanks for two years before you start selling them. That can be done, but selling them in twos and threes to private buyers isn’t going to fund that Porsche anytime soon.
To make it a business, you’re going to need, say, 100 pairs and several hundred tanks — most of which you’ll be running for a year or two before any selling occurs. Bear in mind that a £100 retail fish might wholesale at about £40 and you don’t make any margin on shipping. Then factor in shipping disasters and so on. At some point in time, heat and food makes it more viable to attempt such an endeavour in a tropical country rather than in chilly old Blighty — unless you really scale up the operation or transport costs rocket.
This is the model being utilised by specialist commercial breeders and I think that given the beauty of the Zebra plec, will ultimately mean we continue to see this species offered for sale irrespective of what man-made catastrophe may, or may not, befall its wild cousins. This is also why I mention breeding this species for yourself. You can get to the stage where you and a group of friends have a decent population of these things and can trade with other groups. Isn’t that a good thing?
Given what I’ve said, perhaps seeking experience, cutting your teeth on less expensive Hypancistrus is a good starting point. If your ambition to keep
these wonderful black and white rock star plecs remains, you’ll be able to give it a worthwhile go and do it in a planned manner. Then you can dream of that first sight of baby Zebra plecs in your tank. That experience is a special thing.
Scientific name: Hypancistrus zebra.
Pronunciation: Hype an siss truss.
Common name: Zebra plec.
Lifespan: 15 years plus.
Spawning age: Around three years.
Water chemistry: 5.5-7.5 pH.
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There are many uses for carbon, especially in the fishkeeping hobby, yet itâ€™s often misunderstood, writes Nathan Hill. Hereâ€™s your chance to get to know this chemical element like the back of your hand.
Look in your tank, it’ll be heaving with carbon. Look at the back of your hand, that’s carbon heavy, too. In fact, carbon permeates all aspects of our lives, from peanuts to pencils. It’s only right we should find many uses for it, and a lot of those uses are aquarium-based.
Carbon is, in its simplest form, the chemical element C. If you know your periodic table, you’ll recognise it as the sixth element down the line. It’s naturally occurring, bountiful and incredibly useful.
You’ll already be deliberately using carbon in some form, whether you like it or not. It makes up a vital ingredient in food, such as protein.
Your fish will be breathing it out through their gills as carbon dioxide. Your plants will be guzzling it up as food to make sugars — C6H12O6. Carbon is absolutely inescapable.
For the best part, most of us will know carbon as the black granular media we cram into our filters. You might have pads impregnated with it, or you might have a pack of it loose, ready to be loaded up into a mesh bag and dropped in the tank somewhere. That’s all well and good, but what does this kind of carbon do? How does it work?
Carbon works on adsorption (not absorption), which is a way of saying it is incredibly sticky to certain chemicals. Once certain chemicals come in to contact with carbon, they are grabbed by it and retained — at least for a while.
This is why the surface area of carbon is all-important. The more it has, the more waste it can hang on to. This is where activated carbon has the advantage over regular carbon, in that the activation process massively increases the number of tiny pores in it.
Carbon is excellent at removing organic chemicals from the water. Now, don’t confuse organic chemicals with the three usual suspects: ammonia, nitrite and nitrate. These three are inorganic compounds, and carbon has no interest in them. If you’re adding carbon to deal with an ammonia spike then you’re barking up the wrong tree.
The two chemicals that carbon excels at pulling from tanks are phenols and tannins. These are produced from a variety of sources, including the metabolic waste of fish, leaching from wood, the breakdown and decomposition of faeces, plants and uneaten food, and more. You’ll recognise them as chemicals that discolour the water, giving a yellow or brown tint, and in the case of phenols, emitting a 'tanky' smell as well.
In this respect, carbon is indispensible in polishing the water and keeping it gin clear. For marine keepers, those phenols can play havoc with marine invertebrate growth, where for freshwater they’re more likely to build up and cause eventual malaise in the fish.
It’s essential to get carbon in the right place in the filter as well. If it is placed too early then it runs the risk of becoming biologically active; that is to say that it will start to get smothered in nitrifying bacteria. If that happens, you lose surface area on the carbon and it becomes redundant. Even worse, when it comes to changing it, you’ll be pulling out a huge glut of your biological filter with it!
The carbon should always be a polishing agent at the end of the filtration process, never at the start. If you have a canister then you want to go foams (mechanical filters) then biological media and then carbon, not the other way around.
How much you need to use varies, based on your tank, the inhabitants and the quality of the carbon. The best carbon you can get has the highest surface area to volume ratio.
If faced with a choice of a few varieties, opt to buy the one that boasts the most surface area compared to its weight. Some brands will happily advertise their surface area on the packet, and this is a good sign that they know what they’re talking about.
Carbon as filter food
In marine tanks, carbon is frequently utilised as a way of encouraging and feeding the growth of anaerobic bacteria.
Anaerobic, heterotrophic bacteria — the kind that guzzle nitrates when there’s no oxygen around — require a carbon source in order to function, unlike the autotrophic bacteria in our filters that convert ammonia and nitrite. That carbon can take a few forms. Some newer products are appearing that use a starch as the carbon source (and with excellent results, I add).
The traditional method is to add a liquid carbon, namely alcohol, to the tank. The alcohol we have in drinks like vodka is ethanol — C2H5OH — which is just right for the bacteria to use. It might seem odd, but, yes, adding the correct amount of vodka to a marine tank with plenty of live rock will reduce both nitrates and phosphates. Different aquarists have had successes with different rates of vodka dosing, but methods that have worked have involved between 0.1 and 0.9ml of 40% alcohol vodka per 100 litres to a tank daily.
Of course, vodka isn’t the only way to get carbon into a tank, but it has given good results so far. Some aquarists have experimented with other ‘everyday’ sources such as vinegar, rice and sugar. The angle here is that these methods introduce carbon to the water column. The catch with that is that there’s every chance an overdose will poison fish. Uh oh.
That doesn’t spell the end for carbon dosing. In the wake of dangers presented by liquid carbons, the market has increasingly steered towards solid carbon sources, namely starches and other carbohydrates, or ‘dry vodka’ dosing. Don’t be deceived by the 'vodka' part in this latter claim, as vodka is not an ingredient at all; it’s just a direct reference to the fact that it’s doing a similar job to vodka dosing methods.
Solid carbon reverses the roles a tad, and rather than bringing carbon to the bacteria (who usually live in rocks or substrate), this method entices bacteria to grow directly on the carbon source. Most solid carbon methods employ the use of a reactor, which is a large tube through which the water from the tank passes over the carbon filter medium. This has the effect of tumbling the media and keeping it in suspension, and as the carbon then develops a film on its surface — made up of nitrate and phosphate-guzzling, carbon-hungry bacteria — this tumbling action knocks the excess biofilm off.
The film now comprised of bacteria and fixed waste, is then either removed through the action of a protein skimmer or is even consumed by corals and other invertebrates in the tank.
Flow rate is essential when it comes to solid carbon dosing. Too fast, and the filter doesn’t become established; too slow, and everything gets smothered in biofilm. Solid carbon is still a fast growing part of the marine fishkeeping hobby.
Carbon as plant food
Carbon is essential for plant growth, but it needs to be in the right form for plants to uptake.
I’m sure most of us are well aware of what photosynthesis is, but to briefly recap it’s the action of plants that utilises water, light and carbon dioxide in order to create carbohydrates and oxygen.
In the aquarium, carbon is added in one of a couple of ways. The preferable method for many is to add carbon dioxide to the water, through the medium of tiny bubbles until it forms a solution in the water. As humans, we guzzle down the stuff as the main ingredient in fizzy drinks: carbonated water. One alternative name for carbonated water is carbonic acid, and that’s one of the reasons why soft drinks are so acidic: because you’re literally drinking acid. Add too much to the tank, and it’ll drop to dangerously low pH levels, which is why a thorough understanding of the use of CO2 in planted tanks is essential and why so many 'budget' CO2 kits can, in fact, be wildly dangerous.
In absence of adequate carbonic acid, plants in tanks will try to find their carbon from elsewhere. Calcium carbonate, the chemical responsible for the alkalinity and carbonate hardness in your tank, is sometimes forcefully secured as an alternative source and can result in faint chalky deposits on plants.
Carbon can also be added in liquid form, and the current vogue of plant growers is the use of glutaraldehyde, CH2(CH2CHO)2. This form of carbon is not without its risks. In fact, in its everyday use, it’s a steriliser for dental gear, a wart cure and a fixer for tanning leather. Overdose it and it’ll ravage fish and invertebrates.
Carbon as dechlorinator
One area where carbon is outstanding is in the removal of chlorine, chloramine and some heavy metals. With that in mind, it’s a pristine choice to treat any incoming tapwater before use with fish, and it can be considerably more economical than using liquid dechlorinators (some of which don’t even remove chloramine!)
To put into context, a typical 500ml bottle of dechlorinator will cost me about £9 and treat around 19,000 litres. Ten bottles will treat about 190,000 litres and cost me £90. A typical carbon dechlorinator treating 350,000 litres can be picked up for around £90 to £115. That’s a big saving…
A carbon dechlorinator goes inline on your water supply. Some need to be permanently installed, which is great for domestic supplies as well as tanks or, if you prefer, you can buy units that simply go inline with hosing.
You pay your money and take your choice.
The lifespan of carbon
Due to its adsorptive nature, carbon eventually exhausts itself when its entire surface is coated in waste. Anyone that tells you an exact lifespan for carbon is a barefaced liar, as each and every tank will have a different volume of waste inside it. In some cases, the carbon might be exhausted within three or four weeks. Most users will have it in their tank for up to six week stints at a time, after which time we generally accept that it can start to leach some of what it has taken out back in to the water.
In that time, you’ll find that carbon is very good at removing chlorine; chloramine; phenols; dyes; some heavy metals such as tin, mercury and iron; and fish medications. Indeed, that’s one of the best reasons to have carbon on hand: to whisk out any accidental overdoses or to remove residual medication after a disease treatment.
PFK answers your frequently asked carbon questions
Where is carbon from?
Carbon comes from lots of different sources. On a universal level, it is formed in the death throes of exploding stars and blasted out into space during their final cough.
For aquaria, granular carbon can come from animal bones, peat, coconut shells, wood and bituminous or lignite coal. The source can have a big effect on just how good a carbon is in action. Effectively, all carbon is just charcoal taken to the next level by cooking it.
To create carbon, these ingredients need to be heated to thousands of degrees centigrade, which gets rid of the impurities and chemicals you don’t want, as well as increasing the surface area. Surface area is essential, as the more you have, the more your carbon can interact with water and the more chemicals it can remove.
For filters, it’s generally accepted that carbon made from bituminous coal is the best. In fact, it’s the choice of water purifiers the world over, and if you have a BRITA filter, then you can bet your boots you’ll have this kind of carbon inside it.
Carbon dioxide is sometimes harvested from furnaces, breweries and other ‘recapture’ sources but is also the by-product of burning coke. It can even be made with certain chemical reactions, when acids meet base substances. The kinds of carbon found in solid carbon pellets are often specifically processed starches created in laboratory calibre conditions.
Can carbon be reactivated in the oven?
No. The myth goes that you can place your old carbon in the oven, turn it up to full heat for a few hours and the carbon refreshes. Unless you have an oven that goes up to 2,000°C or more and have access to facilitators like acid and oxygen, then it’ll do nothing. Besides, who can afford to run an oven like that with today’s energy costs?
Didn’t you say it removes organics? What about trace elements?
Admittedly, it’s not just organic chemicals that carbon removes, and as such it has been implicated as a cause of problems to some fish, even as the cause of a disease.
It’s true that carbon is unselective in what it removes. But because of this, it’s had the finger pointed at it for removing trace elements and even micronutrients that fish need. One spurious extrapolation of this idea is that carbon might even cause head and lateral line erosion (HLLE) or hole in the head (HITH) disease. This was touted as mantra by many aquarists for years until further research suggested that it might instead be certain ferrous chemicals used in phosphate removers that were causing the problem.
Either way, the amount of trace elements that carbon can be accused of removing leaves it off the hook when it comes to causing illness.
Do I still need to perform water changes?
Oh yes. Carbon is not a water change in a bag. Despite it pulling out some chemicals, especially dissolved organics, you will still have a build-up of nitrate and a depletion of minerals that need replacing.
Does it leach phosphate?
Yes, the one downside to activated carbon is that it will increase phosphate levels in the tank, which in turn is implicated in the boosting of many kinds of algae in everyday aquaria.
Really cheap, low quality carbon, heaving with ash, will even boost pH in your tank, sometimes dangerously so. As luck would have it, you’ll usually find that these cheaper brands will also be the worst for leaching phosphate, so with carbon it’s often a case of getting what you pay for. If it looks too cheap to be true, it probably is.
Organic or inorganic?
Whether a compound is organic or not rests heavily on carbon, though not without exceptions.
Most organic chemicals that we can think of usually involve carbon in tandem with hydrogen. So, proteins (carbon, hydrogen, oxygen and nitrogen) and sugars (carbon, hydrogen and oxygen) are among the many organic chemicals that we come across.
It’s not quite enough to class carbon as the single factor, however, and not everything carbon-based is organic. A diamond, for example, is pure carbon, but as inorganic as it gets. Carbon dioxide (carbon and oxygen) is another inorganic carbon form. There are even a couple of organic compounds that do not have the hydrogen bonding, yet they are still classed as organic.
It’s rare that you’ll come across the phrase organic or inorganic carbon in the hobby, but if you do, just know that what we’re referring to is the presence or otherwise of both carbon and hydrogen in a compound!
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With comic canine faces, bird beaks, quirky lips and more facial expressions than Jim Carrey, pufferfish can evoke a smile from even the sourest of sourpusses, admits Nathan Hill.
The most enduring, admired and adored fish in the hobby have to be the many pufferfish varieties. Traditionally speaking, the challenges of keeping puffers have been split into three categories: size, salinity and temperament.
The size issue is mostly a marine problem. Huge Dog-face and Porcupine puffers are far and away the most appealing, but also the largest, as though their cuteness is directly correlated with their size. These bloated jesters, reaching 50–60cm/20-24" or more, are not for the starter aquarist. Nor many experienced ones.
Salt has been the bane of many puffers, mainly because there seems no 'folk wisdom' consensus on exactly which species require brackish conditions, full-blown marine or fresh.
For years, there has been confusion about exactly how much salt to give a Figure eight or Green spotted puffer, resulting in errors, white spot and death.
And lastly, there’s temperament. Pufferfish are well armed, with slicing ‘beaks’ and a tenacious lust to bite absolutely anything that can be bitten. It’s as though they explore the world with their teeth as a primary sense organ, such is their propensity to chomp.
This means that almost everything that has been housed alongside traditional pufferfish has ended up either shredded or decapitated, resulting in lightly stocked tanks and heavy disappointments.
This all changed when the world’s tiniest bundle of adorable appeared in the hobby. The Dwarf Indian puffers, also known as Pygmy puffers and Malabar puffers, Carinotetraodon travancoricus, were a revelation for the everyday aquarist, being small, entirely freshwater and not quite the relentless psychopaths that we naturally expect of any of their relatives. That’s not to say they’ve been problem free.
In some cases, enthusiastic buyers plunge them into community tanks where they immediately race over to say 'hello' to the resident Siamese fighter in the same way my Scottish terrier tries to say 'hello' to squirrels. A little foresight regarding tank mates can go a long way.
Avoid wild fish
The home aquarist should be mindful to try to avoid wild caught specimens when purchasing pufferfish, due to the impact that the hobby, along with other factors, is having on wild stocks. Though some researchers want to classify Carinotetraodon travancoricus as endangered, the IUCN (International Union for Conservation of Nature) Red List sees it fit to class them only as vulnerable. Overfishing for the hobby is cited as one reason, though damming in India, aggressive agriculture and deforestation all plays a part.
The figures suggest that over a five-year period, wild populations fell by up to 40%. Ask your retailer the origins of the fish before buying, as this is one situation where farmed or locally bred fish may indeed be preferable.
Pygmy puffer popularity means that you’ll find these fish in dozens, if not hundreds, of stores around the UK.
Check for plumpness and condition before buying, as some are sold in an undernourished state. If you can, request to see the fish feeding before making your decision.
Being small and readily available, expect to pay anywhere upwards from around £2 per fish, and ask if there are bargains on buying numbers. Remember to keep eyes open for farmed puffers over wild!
Are pygmy puffers poisonous?
Probably not. At least, not in the same sense as their larger Fugu cousins. Puffer poison is well understood in popular culture and not just as a recent phenomenon. Even Captain Cook had a run in with the stuff when half of his sailors fell ill from eating puffer flesh and all his pigs died.
The poison in question is Tetrodotoxin, or TTX, a frankly horrific neurotoxin to succumb to. Eat the wrong bits of Fugu and your body shuts off while you remain conscious. All the involuntary muscles such as the heart and diaphragm stop, and you die. You don’t need much of it either. As much as you can carry on the head of a pin will easily kill an adult human.
Female puffers are thought to be more toxic than males, with ovaries being able to store more of the poison than testes.
Marine puffers might make their own toxin from symbiotic bacteria. However, they might gain it through eating other organisms that produce it such as the algae on the shells of certain shellfish. In the confines of a tank, without access to toxic food sources, there’s little reason why we should expect Carinotetraodon to become too much of a health hazard. That said, you still wouldn’t want to eat one. That’d just be silly.
How to set up a Dwarf Indian pufferfish tank step-by-step
I took the chance to rig up a Fluval Fresh 85 l/19 gal system that I have been sat on for a while for my pufferfish foray.
Once filled with sand and décor, I calculated the volume to be closer to 60 l/13 gal of water, which is perfect for a shoal of six Carinotetraodon travancoricus.
Here’s how I did it...
1. The tank is cleaned and placed on pieces of trimmed absorbent matting to balance out any irregularities between glass and cabinet. The filter and lighting are then installed.
2. Two pieces of lava rock are added at one corner to act as the foundation to build up my ‘riverbank’ edge. I have chosen the side with filter pipes to help obscure them.
3. A single central piece of presoaked Redmoor wood is added to provide an intricate structure for the puffers to explore. It is vital to soak this wood in advance to stop floating.
4. Approximately 15kg of thoroughly washed aquarium silver sand is added to the foundation rocks to create a deep bed. The sand is smoothed down with a credit card to shape.
5. A large flat cobble and smaller subordinate cobbles are added to the middle of the tank. They help to reduce 'sandsliding' and create a transition from flat to bank.
6. Loose twigs are added for effect, and the two marginal pond plants, Equisetum japonicum, are removed from their pots, the roots rinsed and then added to the bank to break the surface.
7. The tank is filled and six bunches of assorted Vallisneria sp. are divided up into individual plants and added to the display using pinsettes, but only along the back and side.
8. The heater is added, and floating ‘nuisance’ plants and algae, taken from a retailer’s pond plant vat, added to the surface. These help reduce the impact of the LED lighting.
- Fluval Fresh 85 l/19 gal aquarium with filtration, heating and LED lighting
- 15kg aquarium silver sand
- 1 medium piece Redmoor wood
- Approximately 6kg of lava rock
- 4-5kg of assorted cobbles, including one large flat cobble
- 2 x Equisetum japonicum pond plants
- 6 x bunched Vallisneria
- Floating duckweed and algae
On the whole, keeping Carinotetraodon travancoricus is so easy you’ll be left wondering why you don’t have tanks of them all over the house. The only single, difficult aspect is feeding, but as long as you’ve got a freezer, then you can easily overcome that obstacle.
By way of return for meeting their requirements, they’ll reward you with some of the most comedic antics that any fish can muster. Give them time and they might even start to breed for you too, without any extra outside help.
Even an old sourpuss like myself has to admit that I spend way more time watching my puffers during the evening than any other fish I’ve owned, and to date I’ve never been able to second guess quite what they’ll do next. Join the pufferfish camp, and I doubt you’ll ever look back.
Dwarf puffers hate flake foods. Offer it and they’ll look at you with indignation. They’ll potter across for a curious scan over then let that flake slump to the base, where it’ll sit festering.
Bloodworm is never refused, either live or frozen, and other foods are accepted according to individual fish temperaments. Some will also gorge on frozen Daphnia or Cyclops, some will only accept live.
The same applies to brine shrimp and Tubifex. Invest in a mixed pack of frozen foods, such as a quintet with five different ingredients and see which your fish prefer.
Many larger puffers suffer from dentistry issues in aquaria, as their sharp beaks (actually four fused teeth) aren’t worn down from foraging food and crushing mollusc shells. Carinotetraodon succumb less, but it is still something to be aware of, and their diet should include creatures with a hard shell that needs biting through.
Snails are a good choice, and if you know other fishkeepers, I’m sure they’ll be happy to let you take some of theirs away.
Daphnia are another option in helping keep teeth trim and you should make a note to pick up some live ones whenever you see them offered.
Their tank need not be particularly big, unless you’re housing a shoal of them, which you definitely should. Wild Dwarf Indians like to move in large collectives; this is why they’re so easy to catch, and they have a migratory, cyclical lifestyle.
Despite their waspish nature to some other fish, they do enjoy the company of their own kind. Because of their adult size of a mere 3.5cm/1.4" for wild caught specimens and an optimistic 2.5–3cm/0.9-1.2" in aquaria, they’re suited to anything around the 60cm/24" long mark.
Keeping them at a density of one fish for every 10 l/2 gal of swimming space is a pretty safe bet, as long as the sex ratios aren’t skewed heavily towards males. Males will bicker and squabble, and there’s some evidence to suggest that in a young group, the first fish to take male sexual development will release pheromones to inhibit the sex changing of its contemporaries.
Water quality needs to be pristine, and an oversized, but underpowered filter is advised. Their wild waters are slow moving and they don’t have the body shape for turbulence. Where other fish may be streamlined and hydrodynamic, cleaving through water like aquatic gazelles, puffers tend to have all the manoeuvrability of an inebriated cow. Opt for filters that can spread any return flow to the tank over a wide area, minimising any fast torrents or eddies.
Biologically speaking, the filter needs to be big as the fish are messy. With vast appetites and an affinity for spitting chunks of food out, expect pollution to be erratic in poorly managed tanks. Getting in to the habit of removing uneaten scraps with a net or siphon hose after each meal is good practice.
Water chemistry can be slightly acidic or surprisingly alkaline, with records of the fish being collected in rivers anywhere between 6.8 and 8.3 pH. Hardness is equally diverse, and anywhere between 5 and 25°GH they are fine.
Temperature should sit between 22 and 26°C/72 and 79°F, though wild samplings have revealed fish from rivers in excess of 33°C/92°F during summer months.
Decoration is where the aquarist should be indulgent. Unlike many fish that glide about like automated submarines, oblivious to everything around them, Dwarf Indian puffers need to be enraptured at all times. To them, the world is one fascinating place to be explored on the smallest level, through the medium of eyes and teeth.
Wild habitats involve plenty of leaf litter, marginal vegetation and fallen branches, but in aquaria, anything that can be explored will keep them occupied. Be creative with caves, make dense thickets of plant and add as many anomalies as you like — I’ll even forgive the air-powered scuba divers — and they’ll love you for it.
Aim to break up line of sight in case any bickering does occur. Puffers tend to be angry only for as long as they can see the object of their rage. The moment it’s gone, they’ll swan off in child-like wonderment to look at a plant stem, piece of gravel or upturned leaf instead.
Sexing the dwarf puffer
Sexing Carinotetraodon revolves around colours and markings. 'Wrinkly' eyes, actually a scribble of fine lines around the orbits, indicate males, as does the presence of a clear, dark line that runs lengthways over the belly. Males supposedly have a slightly yellower underside, too.
Add other fish at your peril!
Anything slow or cumbersome will be nibbled, and even fast fish such as danios can receive the occasional sly nip.
Shrimps are generally a no go, unless you want them dismembered, and snails are right out; some keepers have managed it, but they’re certainly the exception rather than the rule. Unfortunately, each fish has an individual temperament, so I can only advise you to err on the side of caution. I’ve seen Dwarf Indians kept with guppies, gouramis, catfish and even crabs, but I would only ever consider species-only tanks.
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Nathan Hill explores the origins, benefits and breeding of one of the hobbyâ€™s biggest game changers, the Amano shrimp.
I’m not sure aquascaper Takashi Amano realised just how much he’d change the face of fishkeeping when he asked a local collector to round up a few thousand bland, colourless shrimp for him. Now, three decades on, there are few tanks that haven’t felt the presence of these hard-working, tenacious invertebrates.
My own experiences with these fastidious grazers have been positive through and through. They’ve saved aquascapes as well as my large retail displays (in my aquatic store manager days) and I’ve even had them breed, which is something I didn’t know was remarkable at the time and something that many Amano shrimp adherents will vehemently deny; more on that later.
The true Amano shrimp is Caridina multidentata, but you might see them bandied about under their synonym of Caridina japonica. Certainly when Takashi stumbled across and popularised them in the 1980s, that was the name they were recognised by. It was only in 2006 that revision took place and gave them their current identity of C. multidentata.
If 'japonica' sounds a little Far Eastern to you, then you’re on the right track. This name refers to their Japanese heritage, where Takashi came across them and where many come from today. The original specimens were recorded from the Ogasawara (or Bonin) Islands, though they’re just as happy on mainland Japan too.
Some folks have the impression that Amano shrimp only come from Japan and its immediate vicinity, but this is far from true. In reality, Amano shrimp are also found in Taiwan, the Ryukyu Islands (between the Philippine and East China seas), Fiji and maybe even Madagascar, though this is unlikely. There was contention over the validity of the Madagascan shrimp. As far back as 1965 taxonomists (namely Dr Holthuis) have been marking them out as different and have cited features such as moving rostral teeth as adequate features that have granted them their own species status.
There’s even the strong chance that some of the Amano shrimp on offer in the trade are not true C. multidentata. Caridina make up a huge genus of approximately 280 different species spanning across Asia, Oceania and Africa — there’s even a Caridina species in Lake Victoria. With such an abundance of species, many physically very similar, it’s easy for imposters to slip under the net and enter aquaria. One shaky train of thought is that many 'Amano' shrimp on sale are not true, Japanese specimens but a Taiwanese variant.
These 'Taimanos' are identified by two features: the first being their shorter, compact rostrum, and the second being their inherent laziness. Supposedly, these false shrimp also breed entirely in freshwater, which is something that C. multidentata do not do. But aside from that they have the same, nondescript colours and similar markings.
There are even hints of an Indonesian variant doing the rounds, but these are also contested on a species level; they have a straight rostrum and not a crested one. Buyers beware, and be diligent. True Amano shrimp should be relentless workers, and that’s exactly what fuels their popularity. Tirelessly padding away with their tiny maxillipeds, they will graze on almost all forms of algae with just the dreaded Black beard algae and some cyanobacteria types being sometimes averse to their palates.
Lacking cutting or biting mouthparts, at best they can softly rasp away at surfaces taking away the topmost film. This inability to cause harm makes them ideal workers in tanks where there are small fish and even fry, which they will largely ignore. My own experiences have seen the occasional, bold Amano tootling off with a prize in the form of a fish egg, but their impacts on breeding populations are negligible at best.
Some aquascapers have griped and bickered that their Amanos have damaged planting, but this is unfair condemnation. Amano shrimp will indeed rasp away at plants but are only able to take away material that is already dead or dying. It’s not unusual to find perfectly cut holes in leaves, where plants have degraded through nutrient deficiencies and the shrimp have cleaned the site up. Much like maggots in a wound, they’ll only eat the bad and leave the healthy.
Second to none
The benefit to the aquarist in keeping these shrimp is huge. Their eating efficiency and digestive capacity is second to none, and, in part, a reaction to what can be an oligotrophic lifestyle.
In the aquarium they will pick up on almost any waste, be it uneaten food, fish faeces, decaying plants, or whatever, and convert it into tiny packages of shrimp waste, almost like large grains of jet black sand. These can then be easily siphoned from the tank during a water change.
Regardless of how good a cleaner they are, remember that Amano shrimp do not impact on nitrate levels at all. It does not matter if you have ten or two hundred of them, you’ll still need to water-change just as frequently!
There’s little reason to consider a biotope for these creatures, but if the idea appeals then simply go in for a large tank with big rocks and boulders inside it. Alternatively, Amano shrimp can be found in swamps with a handful of mossy plants and organic litter.
Don’t be scared of a little turbulence either. In their natural range, Amano shrimp are often subject to middling to strong flows and have a better grip on surfaces than you might expect.
Tolerant creatures (Picture above by George Farmer)
Amano shrimp tolerate a range of water conditions with the exception of the usual suspects that are ammonia and nitrite. Some sources cite Caridina as being indifferent to nitrite, but this isn’t always the case. Although nitrite reacts in different ways to shrimp blood as it does to fish blood (contact with the latter forms the lethal methaemoglobin), at high doses it can still cause a degree of mortality and difficulty.
As well as ammonia and nitrite, heavy metals should be avoided so remove any rocks with striated lines of metal through them and avoid lead weights for plants. Although these become issues in mainly softer, acidic water, even in hard systems they can form dangerous levels.
Aquascapers are occasionally worried about the heavy metals found in plant nutrients, but to my knowledge there is no credible evidence that even a major overdose of ferts causes health issues or fatalities in Amano shrimp.
Avoid salt, too. Though this chemical is essential for the rearing of larval shrimp, the adults have no tolerance of it and even background levels used as tonics (3g per litre) can be lethal to them. Hardness needn’t be high, but GH should not be below 6° for successful moulting. Temperatures are tolerated between 18 and 27°C/64.4°F and 80.6°F, and fluctuations between day and night largely ignored.
One area of caution is the use of CO2, especially where Amanos are in planted tanks. Excess CO2 will drive the pH down, and below 6.0pH they will struggle.
They will go up much higher and all the way to 7.5pH without problems. Above this they don’t fare as well and their lifespans will be shortened. Caridina multidentata are pretty resilient when it comes to diseases and aren’t affected by the gamut of usual fish ailments.
White spot and fin rot is not something they’ll experience. In fact, aside the problems of Planarian flatworms that sometimes fight to get under the carapaces of shrimp there are few health issues. Some commercial shrimp suffer fungal issues and many fancy types carry a small flatworm on top of their heads called Scutariella japonica, a miniature symbiont that does little except eat particles of shrimp food and lay eggs in the gills. Amano shrimp, however, seem rarely afflicted by this.
The biggest danger to your shrimp is poisoning, especially from airborne insecticides and more so from imported aquarium plants that haven’t been properly rinsed. Subjected to these chemicals, shrimp will rapidly turn from transparent to white and/or pink and lose all composure and momentum. Shortly afterwards they will be immobile on the base of the tank with only their tiny pleopods twitching, and then they will die. There is no cure for poisoning once it takes hold, so avoidance is the only sure course.
Keep them correctly and you can expect a lifespan of up to four years from your shrimp, over which time they can reach up to 5cm/2" in length.
Choosing the best filter for the job
Filtration for Amano shrimp needs to be unable to suck them in, but they also benefit from having access to sponge filter media where they will nibble at the biofilm and waste contained within. Foam, air-powered filters are a good choice, but better still is the Hamburg mat. This involves placing an entire sheet of foam within two guide rails to create a filter 'wall'. An uplift is then placed behind the mat, just like the uplift of an undergravel filter, and water pulled through the foam and back over the top into the tank.
Hamburgs provide a huge filtration surface, as well as an ongoing source of food for shrimp, and cost pennies to put together. Your local aquatic store can likely give you more advice and the parts required to put one together if you choose.
How well do your Amanos grow?
All crustaceans need to shed their shell in order to grow, and this stage is called moulting.Shrimp moult more when they are younger and, subsequently, growing faster, though adults may moult on around a monthly basis. This also helps to keep the shell healthy and free of pathogens.
With insufficient GH in the water, moulting is impaired. Some keepers rattle sabres over whether or not to leave the shell in the tank once the shrimp has shed.
In theory, the shrimp will ingest some of their own shells and regain some of the valuable chitin within. But in reality if diet is appropriate and GH levels adequate, then this will be surplus to requirements.
That said, there’s no harm in leaving the shell in the tank for grazing purposes.
Differences between prawn and shrimp
People often ask what the difference is between a prawn and a shrimp, and everyone likes to hold a pet theory about what constitutes each.
In reality there is no difference between the two words, and they are arbitrarily assigned to whatever takes the whim of the user. Scientifically the two names carry no meaning, so you should feel free to call your own tank inhabitants a troupe of Amano prawns if that’s what you prefer. So there you have it. Prawn and shrimp are common names, which vary considerably depending on where you are.
If you’re in America you might be sold prawn as shrimp, and in the UK you’ll get the reverse but it’s nothing deeper than that.
How many legs do shrimp have?
Shrimp belong to the order Decapoda, like crabs and lobsters. The common feature between them is that their ancestral progenitor had, at some stage, ten pairs of legs.
Looking at a shrimp it might appear obvious that nowadays they have anything but ten pairs, but the point still holds. They have just adapted and changed the forms and roles of their legs, so that the ten pairs are now divided up between the pereopods, or walking legs, and maxillipeds, or mouthpart legs. The swimming legs, the pleopods, at the rear end are a different matter altogether and are not classed as legs in the same sense.
Copper and crustaceans don’t mix!
Most medications come with clear warnings that they shouldn’t be used with shrimp and for good reason. Anything containing copper compounds is lethal to crustaceans and needs to be avoided.
The reason it is so dangerous is down to the blood of the shrimp. We humans use haemoglobin, which is basically iron that makes up our blood cells, to carry our oxygen around. Crustaceans, however, have blood cells made up of haemocyanin, which uses copper instead of iron to carry oxygen. When using copper-based medications this blood is affected, ruining the crustacean’s ability to ventilate.
Some keepers are reluctant to use water that has been stored in a hot water tank or run through copper piping for fear of contamination, though this only tends to be reported as an issue in new plumbing systems that have not had the chance to calcify inside. An offshoot of having copper-based blood is that unlike our own, which is red, in shrimp and other crustaceans it is blue.
Breeding antics (Picture above by ãµã†ã‘, Creative Commons)
Caridina multidentata is incredibly difficult to breed. Though the leaner males will frequently engage with the plumper, larger females, raising the larvae (sometimes called the Zoea) requires a marine and brackish stage.
Wild shrimp live coastally, where they release their young downstream into the sea. After some four to five weeks, during which the Zoea frequently moult and fatten up on plankton, they become parva, which move back upstream to restart their lives in freshwater mode. This explains their distribution over so many sea bound islands. As the females become increasingly pregnant (or berried) they will show a telltale darkening in the first segment of their abdomens.
My own Amano shrimp bred more by extreme coincidence than skill of any kind. Kept in a 120cm/47.2" cube tank with diabolically slow flow, the tank and adjoining system would be periodically treated with salt to help new arrival fish.
Also in the tank were large, adult Piranha who frequently bred. With ample surface cover in the form of dense duckweed, I would periodically tap the surface growth while holding a net underneath to frighten the Piranha fry into the net. Each and every time I did that, I would yield around 50 to 100 shrimplets for every juvenile Piranha. My only explanation is that with such slow flow and large volume my tank may have developed a slightly saline 'layer' within it, in which the young shrimp had enough salt to survive. Either that, or I had a species that wasn’t the true Caridina multidentata all along.
Other diligent breeders have had stabs at breeding Amanos, usually involving a separate larval system rigged up with seawater, with mixed success. It’s certainly possible to do, but unless you’ve got something close to lab-grade facilities, including plankton sources, then I wouldn’t hold out too much hope for you!
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If Bruce Lee had been a fish, it would probably have been a Siamese fighter! Nathan Hill spotlights this fish from the Far East, which performs just like the martial arts icon - and shows no mercy in combat...
The Siamese fighting fish is a dual-purpose animal. Depending on its audience, it might be brightly coloured with draped fins trailing. It may be compact and squat, short fins pert and erect, drab coloured and with a head full of mean thoughts.
Both examples are of the same fish: the Far Eastern Betta splendens and one of the most contentious pets in the hobby.
Plakats, the true Thai fighters, have long histories. Indigenous Thai peoples have probably kept them for 700 years or more. Farmers, began collecting and breeding the fish they found in rice paddies but, due to increasing use of agricultural chemicals, not so many are found there today.
Official reports of fights began in the 1800s and the King of Siam — as the country was then known — licensed Betta fights as well as owning a collection himself.
By the 1840s he gifted Danish zoologist Theodor Cantor some of the fish, which Cantor named Macropodus pugnax. Later, the ichthyologist Charles Tate Regan formally described and gave it the name we know it by today — Betta splendens.
Even this reflects a fighting heritage, being named after the Ikan Bettah people of Asia who were fearless warriors.
Fans of Siamese fighters hate misinformation and are keen to dispel 'myths'. Uppermost is that fighters are fine in small, unheated or unfiltered aquaria.
The idea that Betta can thrive in tiny bodies of water emanates from breeders who keep and rear them in cups, bottles, jars or tiny bowls. There are also reports that they are occasionally found in natural pools as small as the flooded footprints of cattle.
It’s hard to believe that a footprint could become a long-term home, though not possible to rule out short-term. Betta countries of origin — Thailand, Malaysia, Vietnam and Cambodia — are subject to flash floods and dry seasons, and the fish might become stranded in pools during receding periods.
It’s also possible to imagine one attempting to cross land, bounding from one pool to another, inadvertantly stranding itself in a temporary body of water mid-way.
Undisputed is that Betta are kept in tiny tanks by professional keepers and fighters, and it’s equally impossible to deny that some of the most visually amazing fish have been produced this way. Their resilient physiology comes into play, along with that perpetually helpful labyrinth organ.
Wild fighter environments are slow flowing. Betta are not powerful swimmers, preferring to use their pectoral fins for mobility. As well as rice paddies, they inhabit ponds, marshes, floodplains, canals and even lazy rivers — but never anywhere torrential.
They live in shallows and need access to the surface. Wild Betta splendens are rarely found deeper than 50cm/20” and any more in a home tank is wasted.
Siamese fighters are obligatory air breathers once past the fry stage. If denied access to frequently gasp they will suffocate. Many fishkeeper newcomers are fazed by this activity, but it is quite natural.
Larger tanks are better and should always be well decorated. Even though fancy Betta in the UK are far removed from their origins they thrive in an environment that mimics the wilderness.
The natural range of a male is around 1m square/ /11’ square, which they prowl for passing females or rivals seeking to expand their own territories
Offer 60cm/24” or more for a male and certainly not under 45cm/18”. Depth is not essential, nor open spaces. Go for dense planting and twiggy ornamentation. Some keepers avoid sharp objects, fearing they’ll tear those delicate fins but, provided the fish isn’t battered by rampant currents, this isn’t an issue.
Any plants are suitable, but if opting for a natural biotope try regional foliage, including Leersia hexandra, Ipomoea aquatic, Ceratopteris thalictroides, Nymphaea stellata, Hydrilla verticillata, Ceratophyllum demersum, Ottelia alismoides and Salvinia cucullata.
However, any dense, bushy planting will be explored, though, come breeding time, the fish may start to disassemble softer-leafed varieties. Planting wants to be intense and the fish are often found nestled among 75% plant cover or more.
Never use tanks with mirrored backs as the fish will react violently to their own reflected image and exhaust themselves trying to reach their non-existent foe.
Placing two males together is a non-starter. Though females are feisty, males contest to the death.
Males and females can be tricky in small aquaria. Males often reject the female’s presence until ready to spawn and domestic assaults are commonplace.
Females are identified by their shorter fins, smaller bodies and smaller 'throat flap' which males flare in combat. When they first meet he may flare, while she develops a dark bar on her flank. Rival males don’t do this and respond to flaring with reciprocal flaring and attacks.
Long finned or Betta-looking fish may be seen as rivals and treated accordingly. Long-finned guppies have also been savaged by a jealous fighter.
Fancy fighters are also delicate flowers. Many other fish cannot resist those long fins and certain barbs and tetras can strip a Betta to a ragged sausage in minutes!
Don’t confuse 'fighting' fish as meaning that they can hold their own against allcomers. The faster, more agile and curious will shred a Betta and once those fins are stripped any recovery will take months — if ever.
Fighters won’t tolerate poor water quality. Though they can exist in water with low oxygen and high carbon dioxide, they don’t always thrive in polluted waters.
Just as other fish they have no defence against ammonia or nitrite poisoning, aside the lowered toxicity of ammonia often offered by their acidic environments.
Aquarium conditions should be as those for other fish, with no ammonia or nitrite and minimal nitrates. Create these with light stocking and mild flow filtration. Avoid any powerful internal or external canisters, opting instead for slow hang-on or air-driven filters.
Native water hardness varies from source to source and readings between 4-20°DH pose no problems. A pH value between 6.0-8.0 will keep all but the most fickle happy.
Temperature is open to debate. Fighters are often marketed for unheated tanks and, although they can tolerate a range of temperatures, thresholds tend to be higher than lower.
Fish kept in cooler water often have health issues relating to slow metabolism and take long to repair after physical damage. They may also develop bloat and become susceptible to pathogenic infections if kept chronically cold.
Most keepers opt for between 24-30°C/75-86°F, as there’s no definitive consensus. Fighting Plakat have been kept up to 38°C/100°F with no ill effects.
Salt is offered to keep fighters in fine fettle, but the benefits are negligible and can be detrimental over a long period. It should only be used to treat specific problems and avoided as a daily tonic.
What is a Plakat?
Plakat translates as 'biting fish'. Technically, a range of Betta species reared for fighting may be Plakat, though in this feature I’m only applying the term to short-finned Betta splendens.
Types of domestic Betta bred as pets, not fighters, are Plakat cheen. These have elegant fins, colourful scales and are less aggressive.
Shorter finned Plakat are Plakat morh, or Plakat luk morh — meaning Plakats from earthenware, pertaining to how they are kept. Having thicker scales, less colour and almost psychopathic aggression, their purpose is clear.
Betta, other than Plakat morh, also appear at bouts. Plakat pah (Plakats from jungle) usually refers to Betta imbellis. Occasionally Betta imbellis, Betta splendens and other Betta species have been crossed to make deceptively powerful but fraudulent Plakat pah. You even have Plakat thung — Plakats from flooded areas.
Fighters are bubblenesters, with the male using his adhesive saliva and pieces of vegetation to create a nest in a quiet part of the tank.
Breeding tanks should be 45 l/9.9 gal or more and plenty of hiding places for the female are sensible. Keep pH at around neutral and temperature at 25-26°C/77-79°F Bare-bottomed tanks will be easier to clean too.
The male and female will come together underneath the nest, becoming intensely coloured, and the two will interlock to form connecting horseshoe shapes. As this occurs she releases her eggs and he his sperm. Afterwards the male collects the sinking eggs and spits them into the nest.
After spawning, remove the female as the male will then turn on her to protect the brood.
Expect the first young to hatch after a couple of days.
During that time he will still look after them. Remove the male from the fry after two days, just before the young start to swim, for at that point he may be getting ready to eat them.
Rearing babies is easy with a mixture of Liquifry no.1, freshly hatched Artemia and infusoria.
Leaf litter will also help promote tiny organisms the fry will browse on as they grow.
Fighters take a wide range of foods, but are happiest grazing through small, live meals.
Colour-enhancing flakes are available, as are dedicated Betta foods, but to see these fish at their very best offer plenty of frozen and live Daphnia, Cyclops and occasionally bloodworm.
Don’t be averse to offering the occasional flaked pea to help stave off constipation and bloat, which fighters can get when fed excess dry food.
Some breeders allow the fish to eat at leisure by having live foods like Daphnia constantly in the tank. Though many fighters are not gluttonous, plenty are fussy and keeping weight on them can become an issue.
Betta can miss out in community tanks with faster fish, so ensure they always get their fill.
Siamese fighters are not long lived. Wild specimens can expect a year or two until conditions such as drought or predation take them and in the aquaria don’t expect them to reach ripe old ages.
Bear in mind that the fish sold in stores will already be around six months of age, so expect a realistic year to eighteen months from them.
There are many reports of domestic fighters reaching four or five years in the aquarium and there’s one contentious report of steroid use prolonging life to more than seven years.
A taste for almond
Plakat breeders and keepers have long recognised the merits of having almond leaves in Betta tanks. Not only do these acidify the water as they release tannins, but also have health benefits.
They contain antifungal and antibacterial chemicals for their own protection and these leach into the water where they have a mild disinfectant value.
Some chemicals are known, like the flavonoids quercetin and kaempferol. Other constituents like saponines and phytosterols are also present and almond leaf derivatives are often used as herbal medicines.
These agents aid recovery in true fighters and it’s thought that the presence of almond toughens the scales and skin to make them more durable battlers.
Are fish fights still legal anywhere?
Put two fighting fish together in the UK and you’ve violated the Animal Welfare Act, facing a fine and ban from keeping fish.
However, other countries have more vague legislation and Thailand is introducing a range of measures which would also end cock fighting there.
Restrictions on fighting fish are in place there but not from a welfare perspective, rather on volume of unregulated gambling. At the moment you can fight, but can’t put money on any outcomes.
Other Far Eastern countries have taken mixed and contradictory approaches and contests still regularly take place in Cambodia, Malaysia and Vietnam.
Genetic strains of fighting fish
Wild Betta splendens have experienced selective line tinkering and now a vast range of colours, fin and body shapes are available. These include, but are not limited to:
- Plakat – wild-type fighter.
- Halfmoon Plakat (HMPK) – short ‘D’ shaped tail.
- Crown tail Plakat – short tail but heavily spiked.
- Veil tail – long, drooping tails and most commonly seen on sale.
- Crown tail – like the Veiltail, but with extended fin rays, giving ragged effect.
- Comb tail – a crowntail with much shorter extensions.
- Spade tail – tail culminates in sharp point.
- Halfmoon – tail ‘D’ shaped, but not over 180° spread.
- Over Halfmoon –short tail spreading more than the 180° ‘D’ of a standard Halfmoon.
- Delta tail – tail with less spread than a Halfmoon, with sharp edging.
- Halfsun – Halfmoon tail with slight crowning.
- Double tail – tail split so that top and bottom halves appear distinct.
- Rose tail – overgrown tail which appears ruffled and rose-like.
- Dumbo –variant with hugely enlarged pectoral fins, like elephant ears (pictured above).
New crosses and finnages are constantly being developed and it’s not unusual to encounter a mixture of shapes and strains.
The making of a champion
In Thailand there’s more to fighting Plakat than just putting two together and (illegally) placing bets. There are distinct fighting characteristics as well as different Plakat forms.
Considerations include family, using phrases like ‘harsh’ or ‘crazy’ to describe its background. There’s bloodline or origin and age, though colour is less of a factor.
Fish will be categorised by fighting style, using terms like ‘strong mouth’, ‘chase’, ‘force bite’, and ‘good skin’. Fighting focus is recorded as ‘face’, ‘fins’, ‘stomach’, ‘ear’ and so on. Even teeth types and stamina are taken in to account.
Good history fish command high prices and figures of US $65/£42.50 or more per fish are not unknown.
Four forms of Plakat body shape are usually recognised.
There are snake-fish head/long bodies (Plachon) noted as fast, aggressive and with sharp bites; short head/short body types (Plamor) considered slower, but tough; sharp curve mouth/long body types (Plakrai) being very fast with strong bites and the hybrid (Plasang) which is often a smaller blend of wild and line-bred fish.
There are also noted styles of combat and techniques include double hits, turn-back hits and even persistent hits.
If a fish loses a bout but survives, he may be released back into the wild, or, if he showed potential, used for breeding. He may be retired and kept as a pet, or even end up in a water tank to help keep nuisance mosquito and midge larvae in check.
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Nathan Hill reveals a fish more feared for its hunting prowess above water than in it.
For many, the Silver arowana is the definitive big fish. Related to mighty Arapaima, this fish is not only coveted but in some cases culturally revered — or at least its Asiatic cousins are.
Visually, there’s little mistaking an American arowana for anything else. Having gigantic scales, stylish wispy beards and powerful, sleek body, they look unlike anything else that roams the waters.
South America is home to two species; the Silver arowana (Osteoglossum bicirrhosum) and the lesser-seen Black arowana (Osteoglossum ferreirai).
In juveniles, the differences are quite apparent; one silvery sheened, the other with clearly blackened flanks. In adult form, though there are noted differences in body colour, the most prominent contrasts being in the fins — the Black arowana having considerably darker dorsal, anal and caudal fins, with red and yellow outlines to them on show.
Silver arowana are endemic to South America, in the Amazon basin through French Guiana, Peru and Brazil, and it’s speculated that they haven’t become more widespread only because they can’t navigate rapids and torrential flows.
In the wild, these are spectacular hunters, though at the top of their game above the waterline rather than under it. Their ability to launch from the water has the locals calling them 'water monkeys' — and leaping is something at which they excel.
Reaching for insects
This behaviour is a response to life in the flooded forests where they are common. Here, limited food resources are dispersed over vast areas and niches must be found to exploit what there is.
They are also found hunting along shorelines, inhabiting blackwater lagoons, as well as the littoral zones of rivers and lakes. They are always in shallower areas of water too where the depths offer no benefits.
They launch to snatch at terrestrial insects, but they’re not particularly fussy. Spiders form a large part of the diet, as do beetles, which may be their preference if gut analyses are indicative. Small birds have been eaten, even snakes hanging from overhangs. Other less usual snacks can include crabs, snails and even monkey droppings.
When they leap they often get a side salad of the vegetation the prey had sat on, though it’s not considered essential to offer them green food supplements.
In the aquarium, this propensity to feed from above the waterline is not catered for by all that many aquarists. Instead it’s expected that the fish will take a variety of dried, fresh and frozen foods below the water surface.
Unfortunately this damages the fish and results in a condition called ‘drop eye’ whereby one or both eyes permanently look down, eventually refusing to return to normal. It’s a direct result of adapting to feed from meals on the base of aquaria.
Foreign keepers who use live fish to feed their arowana report the same symptom.
Always try to offer a floating food or train your fish to take from the surface alone. That means interacting and getting involved at every mealtime to get your fish accustomed to feeding from specific points in the tank — and offering a little at a time so food does not sink past.
'Drop eye' also seems more prevalent when these fish are kept alongside other species that swim beneath them.
Some speculate that arowana have superb eyesight and can make compensating calculations for refraction prior to leaping. However, it seems likelier that the reason for the monstrous maw is a morphological offset to compensate for rubbish vision!
Arowana in the wild often take surprisingly small meals per leap, and mouth size may compensate for terrible aim, or at least increase chances of snatching food.
Just because they have an almighty opening they do not necessarily need gigantic meals. Even for adults, crickets and locusts, earthworms, prawns, mussels, cockles and chunks of fish are more than ample.
Striking above or below water affects posture. When priming for an airborne launch they form a spectacular, anguine ‘S’ shape before take-off, though if underwater will often opt for a ‘C’ shaped curve.
Wild fish have been noted to hide behind fallen trees when in hunting mode, curled and waiting…
That gigantic mouth is also used for spawning. American arowana are mouthbrooders, with the male carrying the young a good two months until their yolk sacs are depleted. Often both wild and farmed fish are harvested at this stage, with adult males being frightened or coerced into dropping their young into the nets of collectors and then traded.
Don’t buy an arowana while it still has its yolk sac, as at this stage it will not yet be feeding. Moving yolked juveniles is irresponsible as, if ruptured in transit, the fish is almost certainly doomed.
Spawning arowana form pairs while young, though trying to pair them off in an aquarium is rather futile. Dedicated breeders use huge concrete or clay pools and a massive area is required for success.
Given the high commercial value of exporting arowana, there have been numerous disputes and accusations involving wild harvesters — giant otters once being blamed for reducing stocks, although evidence was lacking.
Given that arowana spawn only once a year, it’s now considered likely that excess harvesting is impacting on populations.
The drawback in keeping these fish is their size. Even aquarium specimens attain around 90cm/36”, and wild fish can be larger still.
Some sources cite a 240 x 90 x 90cm/95 x 35 x 35” tank as sufficient for a single adult, but not everyone would agree. Based on the ‘six times’ rule a 6m/20’ tank is required, which eliminates nearly every private aquarist, aside those with tropical ponds.
Essential if keeping arowana is a well fitting, jump-proof hood. If left open topped they will leap. They just can’t help themselves!
Also be wary for your own safety. That giant, toothy mouth and urge to fly at anything slightly food shaped means that the aquarist can soon become the snack if any food is inappropriately offered via the fingertips.
If wanting to see that jumping behaviour you’ll need long tongs or some kind of feeding stick.
Setting up a tank, aside the size issue, is easy. In a nutshell arowana are not fussed what’s going on beneath them, so décor is redundant. For authenticity opt for plenty of fallen branches, leaf litter and fine sands, but also be aware these big fish also produce lots of waste and frequent water changes, and waste syphoning is essential.
There’s good reason so many Far Eastern keepers opt to house theirs in barren tanks devoid of any décor.
As appealing as these are, don’t be inclined to buy a juvenile unless certain you can provide for it. Young fish are visually more pleasing than adults and it’s easy to get suckered in. Yet later you may struggle to find anyone sympathetic to requests for rehoming and you’ll be lumbered with a fish that may be bigger and more demanding than a small dog.
Scientific name: Osteoglossum bicirrhosum
Maximum size: 90cm/35” aquarium, 120cm/47” wild.
Feeding: Slight omnivore with heavy carnivore leanings. Fish, prawns, mussel, cockle, all insect matter, crab, squid, even some lean terrestrial meats will be taken.
Water chemistry: Acidic water, pH ranging from 5.8 to 7.0, hardness below 14°DH.
Compatibility: It can be kept with other fish too large to be eaten, though this may increase incidence of 'drop eye'.
Distribution: Black and white water floodplains of Brazil, Peru, French Guiana. Introduced elsewhere by humans.
Breeding: Not known in aquaria.
Difficulty level: Juveniles easy, adults extremely hard.
Scientific name: Osteoglossum ferreirai
Maximum size: 90cm/35” aquarium, 90cm+/ 35’+ wild
Feeding: Slight omnivore with carnivore leanings and eats the same as Silver arowana. Wild specimens have even been reported with remains of small monkeys in among gut content
Water chemistry: Acidic water, pH 5.8 to 7.0. Hardness below 15°DH
Captivity: Keep this with fish too large to be eaten, though tank mates may be linked to 'drop eye.'
Distribution: Negro river basin.
Difficulty level: Juveniles easy, adults extremely hard.
Noting the arowana’s large scales, huge mouth and dragon-like appearance, Far Eastern culture associates this fish with money and wealth.
In Chinese culture fish are indicative of abundance, while dragons are associated with wealth and prosperity.
The arowana’s ability to combine the two features in one handy package makes them highly desirable to keep.
Asian varieties are so highly prized that they are even anecdotally connected to some Triad gangs and gangsters.
Post-natal booster food
Arowana make for excellent eating, given their low fat, high protein nature. The Caboclo people of the Amazon feed them to women who have recently given birth, so highly regarded is the fish’s nutritional value.
See some of the other articles in this series:
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When Jeremy Gay persuaded a PFK photographer to finally upgrade his reef tank, it was with the proviso that he helped out with the new one.
If there was one bit of advice I could offer to any reef tank owner, I would say be patient. PFK’s resident photographer Neil Hepworth first got into marines nearly ten years ago, and in that time he has continually run just the one tank.
I helped Neil out with his first tank too, because when he took up reefkeeping he had not kept fish before. It was a 1.2m/4' tank with a wooden cabinet and hood, and I specced it out with a combination of spare electrical goods and purchased products. The tank wasn’t drilled to connect up to a sump, and back then it was an issue just finding a protein skimmer that would fit on such a tank with both a box hood and glass bracing bars.
The initial set-up ran as a basic Berlin system with lots of good quality live rock, powerheads, fluorescent lighting and a protein skimmer. My initial advice was to have just soft corals but within a few years that same tank was home to both LPS and SPS corals. This was achieved without a calcium reactor or supplements, but thanks to Neil’s diligence to water changes and maintenance.
Make no mistake though, that set-up was not without its problems. There were several large wipe outs of corals and fish, many still unexplained to this day, and years of salt spray from the skimmer meant that much of the back of the wooden hood eventually disintegrated.
So, nearly ten years and two house moves later, we were out on a Shoptour, steered cleverly by me to include a tank manufacturer, and Neil eventually agreed to buy a new tank.
Time for a change
Tank fashions have changed quite a bit in ten years, and this time Neil wanted to change the smooth woodgrain of his polished aquarium for the clean lines of a modern-looking gloss white cabinet. I tried to get him to buy a rimless, open-topped aquarium like the one I was planning for myself, but Neil opted for an open-topped pelmet instead. I quizzed the tank builders as to options for the pelmet, because if you make it too high the tank can look top heavy, clumsy and even dated.
We got the pelmet height down to 100mm instead of the usual 150mm or more, and for the cabinet design itself we opted for minimalist design with push open doors, no handles and a very clean, Japanese style.
Marine equipment can look very daunting and nothing is more scary to the inexperienced fishkeeper than a sump tank. It took me years to convince Neil that sumps were better for reef tanks and that, if you do it right, they don’t flood. He wasn’t so sure, but I gave him my guarantee that I would design and build his new tank as if it were my own and that I would run him through what happens in a powercut when we set the tank up. He eventually agreed.
The cabinet was 120 x 75 x 60cm/47.2 x 29.5 x 23.6” so had lots of room for a sump, and I made sure that three large holes were drilled in the back for ventilation. The sump, I told the builder, I wanted to be 91.4 x 45.7 x 45.7cm/3’ x 18” x 18” with three chambers: one 30.4cm/12” chamber to house a nice big protein skimmer, one 45.7cm/18” chamber after that to act as an algae refugium and deep sand bed, and a 15.2cm/6” chamber after that for return pump.
The cabinet and sump were also large enough to include a calcium reactor, phosphate reactor or pellet reactor and an automatic top-up, but Neil felt that the sump and refugium were about as far an evolutionary step as he wanted to take — for now anyway!
I’d played about with quite a few sumps and weirs by the time I helped Neil out with his, so I was pretty clear on what I wanted: a corner weir, ideally square or rectangular, in black, with both top and bottom scavenging weirs to drag water from the surface and from the substrate at the same time.
I also wanted three holes drilled in the base of the corner weir — one for an outlet pipe, one for an inlet pipe and a spare outlet pipe to prevent accidental flooding. I also specified that I wanted room to make one into a 'durso' using 90 degree elbows, and if you ever want to, you could even ask for a fourth hole and pipework to run the pump’s power cables down into the cabinet from the main display tank. The tank builder said they did triangular not rectangular weirs, but they could do everything else I requested.
We could have ordered the bulkheads and pipework from elsewhere, but with there being both metric and imperial pipe fittings and hole cutters out there, one way of ensuring that the manufacturer would drill the right size holes was to get him to supply the fittings too.
One of the most frequently asked questions of the PFK team is how to move tanks. This was Neil’s predicament too, only there was lots of space around it. The tanks were positioned next to each other for the changeover. I supplied lots of empty RO drums, we siphoned as much tankwater as we could in a short time, briefly exposing both rock and corals, and then pushed the old tank out of the way.
Thanks to Neil’s oak floor we just about managed to get some carpet under the cabinet to make sliding it easier, and within five minutes we had turned off, siphoned, slid, filled up and turned back on again, and both fish and corals were none the worse for the experience. That bought us infinite amounts of time to put the new tank in its place and plumb-in and glue the pipe fittings.
My plan was to do the whole changeover within the space of a day. The original tank had a gross volume of about 200 l/43.9 gal, yet the new tank and sump held over 500 l/ 109.9 gal. Neil had an RO unit so I advised him to collect at least 12 drums worth of pure RO before putting it into the pond tub that I lent him, with heaters, circulation pump and airstone to mix up 300 l/ 65.9 gal of salt.
Once mixed he could then pump the saltwater into the 12 drums (hired from an aquatic shop), store them inside the house in the warm and then he would be ready to go on the day of the changeover.
We also made sure we had plenty of buckets, towels, siphon tubes, a new larger heater, a plastic tub to put all the rock and corals into and that no one else would be in the house, or in the way, on that day. I advised Neil to cut feeding down in the days up to the move and for a few days afterwards to cut down waste produced.
With the sump plumbed in and the pipe cement cured in the new tank, it was time to move everything over. My plan was to make the move as seamless as possible by moving all the rock, all the substrate and as much of the water from the old tank as we could.
We placed a black plastic Laguna pond tub on the living room floor and proceeded to move what live rock pieces we could into it. As the water got deeper in the tub, the corals could go in and then the rest of the rock, leaving the old tank clear of décor so we could catch the fish. The fish went into the tub too, along with the old powerheads and heater. Although not lit, this tub would now be perfectly biologically stable for as long as we needed it to be.
The old tank substrate I opted to put into the new tank sump was part sand bed and part biological starter colony. This would move many critters over as well as beneficial bacteria.
The old tank had the now dated rock-wall look, with all the rock being stacked up against the back. From what he had seen in some of the tanks he had photographed, Neil wanted some central rock bommies, which I was more than happy to help with.
I would use acrylic rods to thread the rock onto. Self-supporting narrow bommies mean better water circulation than rock walls and with less detritus build-up or dead spots. We bought some acrylic rods from a reef store, a masonry drill bit with a slightly larger diameter than the rods and in no time had created a bommie stretching the full height of the 60.9cm/24” tall tank.
We then poured all of the new saltwater into the new tank, topped up with enough old saltwater to fill the sump and get the system going, plugged in the new heater and return pump, checked the water and when it was it was up to temperature, moved over the fish and corals.
Yes the water was cloudy, as you might expect, but corals can deal with this and fish and corals were all fine when the water cleared the next day. The old tank was emptied, taken outside and the job done before Neil’s partner got home from work. I got Neil to buy some Spaghetti algae, Chaetomorpha spp, to place into the new sump chamber on the day of changeover. This I advised should be lit 24/7.
Again we built up the new equipment over time, buying from wherever we could. Neil’s always felt a bit guilty about keeping marines so wanted some eco-credentials. I told him LED lighting would be a no brainer and fitted the tank with two TMC Aquaray LED tiles to light each of the bommies and four TMC Aquaray LED strips to provide additional light if needed. The effect is dramatic and striking, and the lack of light spill from the LEDs and the central bommies mean that you get a nice blue infinity effect from behind, aiding the feel of depth in the tank.
The lighting rig also means that Neil isn’t getting heat issues like he did with the old tank; they’re silent because they don’t use fans, they use less energy than his previous lights on a smaller tank, and their slim profiles mean that they don’t protrude past the outer line of the slim, open topped pelmet so the whole build looks really modern and clean.
Neil moved the circulation pumps across from the old tank, but within a few weeks it was obvious that they weren’t moving the water enough. On my advice, and after a talk-through the features, Neil replaced the pumps with two VorTech MP40esW from EcoTech Marine.
Despite forking out a few thousand pounds on the new set-up in all, Neil loves his new tank. With its design and build, the simple methodology it’s running, plus the new lights and pumps, we managed to come up with a reef tank that will last another ten years and has bags of potential.
Being a keen gardener, Neil likes to buy small coral frags and nurture them over time, and the more spacious aquarium and its open aquascape will allow the corals to grow pretty big, without coming up against the confines of the tank walls. As the corals grow and increase in number the aquascape will look a lot better.
Would I have done anything differently in hindsight? Well, Neil doesn’t mind but that triangular corner weir is quite large, a little too large for my tastes. I’ve since bought and long-term tested the discrete Xinout pipe fittings from Italian company X-Aqua on my own tank; they do away with the need for a weir. For the price though, and considering the Xinout’s limited scavenging capabilities, I would still consider a nice black, rectangular corner weir for future projects, and I do still like my rimless tanks with nice chunky Optiwhite glass throughout.
I did set-up such a modern reef tank for myself not long after Neil’s, using the Zeovit method and I really liked it. So, if I had Neil’s tank now I’d run the full Zeovit, Zeolite and bacteria method with an automatic top-up, which is something I wouldn’t be without on any marine tank.
And finally, because the tank is in a lovely large dining room, there’s plenty of space to have opted for a 244 x 60.9 x 60.9cm/8 x 2 x 2’ tank, instead of the 121.9 x 60.9 x 60.9cm/4 x 2 x 2’!
Tank size: 121.9 x 60.9 x 60.9cm/4 x 2 x 2' custom-built tank, sump and cabinet from Aquariums Ltd, which is no longer trading.
Sump: 91.4 x 45.7 x 45.7cm/3' x 18" x 18" with room for protein skimmer and algae refugium.
Lighting: 2 x AquaBeam 1000 Ultra Reef White and 4 x AquaBeam 500 LED strips on MMS mounting system.
Protein skimmer: Hydor Performer skimmer.
Return pump: Tunze Silence 1073.020.
Circulation pumps: 2 x VorTech MP40esW.
Filtration method: Berlin hybrid — live rock, protein skimmer and algae refugium.
Live rock: 30 kilos.
Chemical filtration: API Bio Chem Zorb (carbon) and Rowaphos phosphate remover.
How we created our reef tank step-by-step
1. Polystyrene goes down under the tank and the bulkhead fittings are connected and sealed with silicone.
2. Standpipes are in place, complete with Durso overflow method to reduce noise.
3. The sump is placed inside the cabinet, again on a layer of polystyrene to cushion it.
4. Ball valve and pipework are fitted under the tank. The ball valve reduces noise.
5. Existing live rock, fish and corals are placed in a black tub so that the old tank can be emptied and removed.
6. New bommie formation is created by threading rock onto an acrylic rod.
7. The bommie is lifted onto the rod and placed into the new tank, which is being filled at the same time.
8. Chaetomorpha algae is placed into the algae refugium, along with some small live rock pieces and the old sand substrate.
9. A TMC GroBeam tile is fitted over the algae refugium in the sump, again using a rail system for support.
10. The tank is filled and fish and corals are moved over. The water is cloudy but parameters are stable and match the old tank.
11. The next day the tank is clear and the fish and corals start to make an appearance.
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Gobies can be found in almost all bodies of water, including the coldest oceans to freshwater mountain streams. And there are plenty of marine gobies that are perfect for the reef aquarium, as Dave Wolfenden explains.
Some gobies are so incredibly adaptable that they have even evolved to exploit a partly terrestrial lifestyle in the shape of the endearing mudskippers.
They are all part of the Gobiidae, one of the largest of all fish families, and there’s even a considerable choice for marine aquaria. Despite their small size, these fish can have bags of personality, usually making them excellent reef choices.
Because of their size, gobies should not be kept in the aggressive fish-only system as they will be harassed by many larger species and many predators will snack on them. However, most will be superb for the reef aquarium, providing any chosen tank mates are peaceful.
Certain gobies, though, can be intolerant of conspecifics or even heterospecifics that look similar, especially in limited space.
This is the result of often strong territorial behaviours tying individuals to small patches of home reef. Limit stocking to one goby of each genus unless there’s plenty of room.
Most will adapt well to captive diets and a variety of small fresh, frozen and artificial feeds is important. Many will fend for themselves in a mature reef system with natural plankton populations. Sleeper gobies, for instance, will process the aquarium’s substrate to extract the invertebrate life.
While gobies can find a reasonable amount of food in a typical aquarium, some supplementary feeding will prevent individuals becoming emaciated. Gobies in general fare best in well-established systems and a refugium can help to provide supplementary live food.
Gobies are generally sensitive to medications, because of their scale-less skin.
They’re not the most parasite-prone fish, thanks to their thick mucous coat which helps trap pathogens, but they can nevertheless still suffer from parasitic and other diseases.
Be cautious when treating for ailments. Prophylactic care for newly-acquired specimens is ill advised. Instead, try plenty of TLC and optimal water quality, plus plenty of food. If medication is necessary, don’t overdose.
When selecting specimens, avoid any looking emaciated. These may have been starved for some time and are too thin to recover.
Which species of goby is right for you?
Some of the most commonly encountered gobies in the marine hobby include Sleeper gobies (Valenciennea) which are prodigious sifters of sandy substrate, hence the alternative name of sifter gobies.
These spend much of their time ingesting sand and extracting tiny invertebrates. For this reason, they can be used as efficient cleaner crew as their constant turning of the substrate helps to maintain the sand bed.
Ensure rockwork is securely placed, as meandering gobies can easily topple piles of live rock.
Bear in mind too that they may frequently spit mouthfuls of sand over corals and other invertebrates, so strategic coral placement must be a consideration.
Blue-cheeked sifters (V. strigata) — pictured above — are often imported from the Indo-Pacific. Specimens grow to around 15cm/6” in the aquarium and earn their common name from electric blue markings on a yellow face.
Also noteworthy is the Chalk goby (V. sexguttata), again from the Indo-Pacific and reaching a similar length.
The Jam sandwich goby (V. helsdingenii) from the Indo-West Pacific, with its alternate black and white bands, looks particularly striking and again is a very attractive reef addition.
This species will reach 15cm/6” and it’s worth trying to establish pairs, as males are identifiable courtesy of their elongated dorsal fin filament.
Neon gobies are the alternative cleaners (picture above by Nick Hobgood, Creative Commons)
Several species are known collectively as 'neon gobies' and belong to the Elacatinus genus – formerly Gobiosoma. Most hail from the Caribbean and other regions of the western Atlantic.
Most commonly offered are the ‘true’ Neon goby (E. oceanops) or the Sharknose goby (E. evelynae) and both grow up 5cm/2”.
Other species may be encountered, although identification can be difficult.
These fish make a viable alternative to cleaner wrasses of the Labroides genus. They adapt well to captive diets, although will supplement diet by performing useful cleaning of 'clients'.
They will set up cleaning stations, but can defend these against other cleaner gobies — so ensure ample room if attempting to keep more than one.
Several genera of gobies form a mutualistic partnership with shrimps — notably Pistol shrimps of the Alpheus genus.
Several genera form such symbioses with shrimps, including Stonogobiops, Ctenogobiops, Cryptocentrus and Amblyeleotris. The basis of this relationship is that the shrimp are good at building burrows but have poor eyesight. The gobies have good vision and are given lodgings in the shrimp’s burrows in return for acting as reliable lookouts.
A shrimp will keep in constant contact with the goby via its antennae and both shrimp and goby retreat to the burrow at the first sign of danger.
If attempting to recreate this relationship, provide a deep substrate of varied material, from fine sand through coarse coral chips to live rock rubble. The best shrimp with which to attempt such a pairing is Randall’s shrimp (Alpheus randalli) — identifiable courtesy of its red-banded legs.
More gobies worth seeking out include the Yasha (Stonogobiops yasha) from the Western Pacific, which grows to 5cm/2”. This is very attractive but pricey.
Also check out the Dracula goby (S. dracula) from the Indo-Pacific, which grows to 7cm/2.8” and sports red and orange bands.
From the Amblyeleotris genus there’s A. aurora (above). The Aurora goby, from the Indian Ocean, grows to 10cm/4” and is stunning with orange bands. A. randalli, up to 12cm/4.7” and from the Western Pacific, has a gorgeous sail-like dorsal fin.
The cool customer
The Catalina goby (Lythrypnus dalli) is sometimes offered — and it sure has that grab factor!
Note that striking range body punctuated with bright blue vertical markings, as pictured here.
However, this species, which grows to 6cm/2.4”, is really sub-tropical from the Gulf of California and surrounding regions. As such it fares best in temperatures slightly below those in a typical reef aquarium, requiring around 18-21°C/64-70°F.
It is possible to maintain, although it requires a dedicated aquarium decorated with coarse sand and rubble, and capable of providing the cooler conditions this fish needs.
As such, this fish should not be purchased as an addition to an existing tropical reef aquarium.
Amblygobius: lovers of midwater
This genus contains a few occasionally imported species and they tend to spend much of their time in mid-water — in contrast to others of the family.
One of the most challenging of the genus is the Court jester (A. rainfordi) — pictured above — from the Indo-Pacific. Growing to around 5cm/2”. This diminutive fish requires copious amounts of filamentous algae, which is lacking in many reef aquarium systems.
Hector’s goby (A. hectori), which is also sometimes referred to as the Gold court jester and from the Indo-West Pacific, assumes strikingly similar markings, albeit with different coloration, and its husbandry needs are comparable to the Court jester
The Banded goby (A. phalaena) is less challenging to look after. From the Pacific, this species reaches 12cm/4.7” and looks stout and chunky, and occurs in various colour morphs.
Banded gobies, as a group, will spend a considerable amount of their time sifting through the substrate for food and will be therefore less reliant on filamentous algae than certain other members of the genus.
Gobiodon gobies get a grip
Members of this genus can usually be found perched on branches of stony corals such as Acropora. Being highly benthic, their ventral fins are often modified into suckers, allowing them to adhere to their host coral, even in some pretty strong surges of water.
These timid fish need to be provided with very small foods, but they can be among the most endearing and best value fish you’ll keep. They’re ideal for smaller SPS-dominated systems.
Particularly engaging is the Okinawa or Yellow goby (G. okinawae) — pictured above — from the Western Pacific. It grows to 3cm/1.2” and sports a white patch on its cheek — the only marking on an otherwise entirely yellow body.
This species appears to be an obligate dweller of Acropora in the wild and the best captive system would also incorporate such corals.
Once an individual is established in the aquarium it will perch on its coral, seemingly demanding all your attention and becoming a true and affectionate pet.
Also noteworthy are the Citron goby (G. citrinus) from the Indo-West Pacific. It grows to 6cm/2.4” and has a distinctive yellow coloration.
There’s also the stunning Green clown goby (G. histrio). This is a striking fish, with red markings on a vivid green body, but reaches only 3.5cm/1.4”. It also originates from the Indo-West Pacific.
Can I breed gobies?
Plenty of marine goby species will spawn in the aquarium if pairs can be established, but many of them are aggressive towards conspecifics.
Many can change sex too, making the establishment of pairs no problem for individuals living in the wild – as every member of the species is a potential partner!
The coral gobies (Gobiodon spp.), for example, appear to be bidirectional protogynous hermaphrodites — starting out as females but can undergo a sex change if necessary.
However, such gender bending is reversible and males may turn back into females if required.
The main challenge with breeding arises from an ability to successfully rear the tiny larvae, which need first feedings of rotifers, followed by enriched Artemia nauplii.
Gobies, however, can be a good bet if planning on a first breeding project for marines. Neon gobies (Elacatinus spp.) are probably the best prospect, as they will spawn in even small tanks if conditioned with varied regular feeds.
PVC pipes will provide a suitable love nest and the resultant larvae should be moved to rearing tanks with identical water chemistry to their original system.
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Is there such a thing as the perfect community cichlid? Nathan Hill profiles a real stunner that certainly comes close.
Cichlids often come with a cost. Some beauties become giants, while others carry psychotic degrees of rage. Some like their water softer than marshmallow and others harder than granite. They are a fickle crowd.
One small group of African cichlids sits somewhere close to a perfect balance. As well as being quite small, their aggression only flares when their offspring are confronted by offending mouths.
They have sublime colours; so much so that their common names reflect this.
They don’t pick on their females, feed willingly, and, if provided with a little privacy, will quite happily go and spawn. And once they have, they’re happy to raise the fry up themselves. These are the Kribensis — fish that have become an aquarium standard for the community keeper.
Technically, the original Kribensis was a single species —Pelvicachromis taeniatus — which was originally misdescribed as Pelmatochromis kribensis (which also managed to gobble up what is now Pelvicachromis pulcher in the confusion) and later revised.
But, just to really confuse things, many aquarists choose to use 'Kribensis' as a colloquial catchall to refer to any of the seven species of Pelvicachromis. For the majority, P. pulcher is the 'standard' Krib and I use that association here.
P. pulcher is an aquarist’s dream. It carries the most startling colours — alternative names are the Palette cichlid, or the Rainbow krib — and it has the pointed trailing fins that one would expect from a far more expensive species. If I had to design the perfect domestic fish from scratch, it’d likely be a Krib.
The only possible drawback to these fish is their innate shyness. Kribs are not especially bold, though there are rare exceptions. To see them at their best, the inclusion of dither fish will be needed — more on them later.
All Pelvicachromis species prefer riverine conditions and are restricted to the African continent: chiefly West and West Central Africa. Only in the rarest of cases do they make an appearance in some slower moving or static flooded area.
P. pulcher inhabits a range from Benin, into Nigeria and Cameroon, and always in similar habitats.
There’s a myth that to this day keeps doing the rounds, unsupported by sound referencing, that Kribensis are found in brackish waters. In reality they cover a vast delta that stretches from around 150km inland to the sea, but repeated surveys have shown that Pelvicachromis are only found in the fresh, usually soft waters, and never in brackish conditions.
The idea of the brackish Krib seems to have arisen many years ago, possibly started by Baensch in his aquarium atlas, but has not been subsequently corrected.
To put the record straight, every bit of quantifiable evidence points strongly at Kribs being obligatory freshwater inhabitants that are quite unsuitable for life in a brackish system.
In studies of their range, the number of collectable P. pulcher substantially drops off as researchers come progressively closer to brackish water regions.
So these fish are not big fans of salt, then.
'Frynapping' (Picture of juvenile above by Tino Strauss, Creative Commons)
Changing sizes of Kribs are found at different points of rivers. The shallowest regions are home to the smallest as well as large numbers of females. Where in most areas a one male to one female ratio is maintained, in shallow regions this tilts hugely in favour of females and 1:2 is the norm. This is most likely a response to predation issues because natural eaters of the Krib — Lates, Hepsetus and Hydrocynus, for example — avoid such shallows. For a young or female Krib, there is safety in a few inches of water.
To further decrease risks, especially those presented to their own offspring, Kribs are known to 'frynap' each other’s offspring or rather to take on board clusters of fry from other breeding pairs. It is suspected that increasing numbers in a brood dilutes the risk of losing one’s own fry to a predator attack.
The fluviatile habitats of Kribs are quite fast moving, with water rushing past at somewhere between 10-50cm/3.9" -19.7" per second. That’s hardly a gushing torrent as you’d find in whitewater areas but a lot livelier than you’ll find in the majority of aquaria.
Such a flow affects the environment that the fish live in, so in this case the presence of fine leaf litter or mulm, which is where Kribs live, is sometimes reduced. Instead, riverbanks tend to be teeming with plant life, and the only debris found is large and heavy with smaller pieces being washed away.
Rounded stones and heavy branches are what a wild P. pulcher would recognise in its habitat, along with a clutter-free substrate of fine and coarse sand, and occasional larger leaves.
There are very few wild P. pulcher in the hobby, and equally scarce are wild specimens of the other Pelvicachromis species, though they do arise. The reasons for this are simple — their origins are dangerous places where the risk of murder or kidnap, particularly the kidnap of a wealthy fish scientist or merchant, is great. Boko Haram kidnappings of western workers are frequent.
To our benefit, the fish breed quickly and prolifically enough for the hobby to be supplied exclusively by tank produced and farmed individuals.
To our loss, we run risks of inbreeding and miss out on huge amounts of potential information about their wild nature.
For example, we know of many colour variations in males of any species of Pelvicachromis, and several populations of each species appear to exist in different regions. It’s not uncommon to see Pelvicachromis species offered with names hinting to their tribe and provenance. One might see P. taeniatus 'Nyete' or 'Moliwe' which will differ substantially to P. taeniatus 'Niger red'.
There are various communities and forums dedicated to the identification and breeding of these variants, and if interested I’d encourage you to investigate because there’s more to it than I could hope to even give an overview of here.
The Krib’s crib
Setting up a tank for Kribensis is easy. Whether you want to slip them into a community or go for something more biotope-based, you only need worry about water parameters for these fish to fit right in.
Plan for a tank of no less than 90cm/36" long. If going for a single pair, 60cm/24" should be
the smallest you use. Though Kribs don’t get huge, they’ll be grateful for extra space.
If planning on biotope, then sand, branches and cobbles are the prime choice of décor. For planting, provide opulent growth. Tangles of Crinum species and banks of Cyperus, Ceratophyllum and Ceratopteris, plus ample Anubias and Bolbitis fastened to the wood will provide abundant cover.
For authentic fish, think of Brycinus longipinnis tetra, and Pareutropius buffei catfish (above). Aphyosemion gulare killifish are abundant in the same areas as P. pulcher and make a pleasing enough companion.
The water for wild Kribs needs to be neutral to slightly acidic with a pH value of between 5.6 and 7.0 and a hardness as low as 2-3°KH. Temperature should be somewhere between 24-27°C/75-80°F for daily maintenance.
However, that’s wild Kribs and the farmed counterparts are considerably more tolerant of a much wider range of conditions.
In the community tank aim for water that is neutral pH, of hardness up to 7°KH, and has a temperature of about 25- 26°C/77-79°F.
Avoid housing community Kribs with other cichlids that may not share the laid-back approach to life. Fish like Blue acara or Jewel cichlids are likely to pick a fight with a Krib and should be avoided.
Likewise, catfish careening about the base of the tank and ousting Kribs from their homes will not be appreciated. House them alongside smaller, peaceful fishes with similar water tolerances for best effect.
One feature that is an absolute must for the Krib tank is the cave. Kribs love to have a home of their own in which they will eventually pair and spawn. This can take the form of an old terracotta flowerpot, a hollowed coconut shell, a custom designed catfish cave, or even a length of large bore hosing.
Whatever you opt for, ensure the Krib has a safe retreat to which it can return at any time. Bare, open tanks will always lead to disaster.
One thing that everyone needs to have a stab at is breeding Kribensis. Few fish display such a vibrant spawning dress, and it is rare for a pair to be so aggressive that either partner is wounded.
Sexing P. pulcher is child’s play, and in the exceptional, rare circumstance that your supplier can’t do it for you then you can step in and easily do it yourself.
In adult Kribensis, the male (pictured above) is always the larger of the pair, reaching up to a maximum of 12cm/4.8". Clear indications of his sex are the design of his tail, which will be slightly diamond shaped. His dorsal and anal fins will be trailing and pointed at the tips. Some keepers like to base sex on the presence of ocelli (eye spots) in the dorsal and caudal fins, but this is not reliable.
Females can display these frequently; even more so with farmed variants.
The male will sometimes have a pronounced red throat, starting at the chin and moving right down over the belly.
Females (pictured above by Tino Strauss, Creative Commons) are always smaller, up to 8cm/3.1" or so, and squat by comparison. They lack the male’s torpedo shape. As long as they’re not stressed they’ll exhibit brighter colours than males too, though note that in the female it is only ever the belly that becomes red and not so much the throat.
The female’s fins are also indicative — her having a rounded, spade shaped tail and rounded dorsal and anal fin tips.
Breeding takes place on the inside roof of a cave after a dance and display during which the female forms a vague 'L'-shape with her body. Spawning activity can sometimes be encouraged by pushing the temperature up a couple of degrees but to no higher than 27°C/80.6°F. Without caves present, expect nothing.
When the pair spawn, there can be some defensive behaviour from the male, who protects the immediate area while the female tends to the young. For the first nine to ten days she may make no appearance at all and will hide away while the male patrols.
At this stage, removing any community bottom dwellers would be wise because they may be struck by the defensive male — especially inoffensive fish like Corydoras that may stumble into the target area quite by accident.
On emergence, you should note quite large fry — which is great as it makes feeding simple! Artemia nauplii are taken (though not ideal), and finely crushed, protein-rich flake food and fry food is soon accepted. Expect the parents to stay with the young for three to four weeks until they eventually start to drift apart.
You need do nothing but feed, sit back and watch as all of this unfolds. And being peaceful, colourful fish in high demand, many retailers are even sympathetic to rehoming your offspring. Get them up to a decent size and you may even be offered a credit note for your efforts.
Note that the pH value of the water the fish breed and rear in has an affect on the sex ratio of the young. At a pH of 7.0, there’s an approximate balance of males to females, though as the water becomes more acidic the number of females increases considerably.
Fresh and green food for thought
All Pelvicachromis species get referred to as omnivores in stores, but the reality is of a strongly herbivorous fish with a taste for algae types and one that ingests a fair amount of sand into the bargain.
In studies conducted on wild fish, crustacean food was found in the bellies of under a quarter of all Kribs with detritus and higher plant matter (fragments of leaves and stems) being found in the majority.
What might be of surprise is the amount of algae ingested. Diatomaceous algae (think the sludgy algae that sometimes occurs on substrates) featured highly, as did blue-green and plain green algae types.
In every single belly looked at, sand was present making it rather clear that the fish were ingesting substrate as they rooted around for algae and detritus. It’s suspected that they even digest the nutritious biofilm that forms on individual grains.
In the aquarium, plant-based foods should be abundant, and Kribs will eventually disassemble softer leafed plants in the tank.
When choosing a food, look carefully at the packaging. Many ‘plant’ foods or algae flakes actually contain very little greenery, and the main ingredient will be fish.
Ideally, you want a veg-heavy flake food if you want fish that aren’t distorted or stunted.
Supplement with plenty of fresh greenery such as blanched spinach and dandelion, flaked pea, and any of the seaweed products frequently marketed for marine keepers.
If you are supermarket shopping, don’t be shy; acquire a little nori seaweed for your fish — I am sure the irony of being fed a sushi ingredient will be lost on them…
What the dither?
Dither fish are smaller fish and cohabit sympatrically with other species. They act as a good indicator to other fish on the presence of predators. Like a landed flock of birds, dither fish will scatter and vanish when threatened.
This presents an excellent visual guide for those fish with the sense to watch them. When dithers are out and about, it’s a good sign that the coast is clear, but if they suddenly disappear then it might be time to do the same!
Small dither fish in aquaria are often species like Zebra danios that are always out and about and immensely active. Their presence reassures more nervous fishes and encourages them to come out of hiding in to the open.
Be careful not to choose dither fish that are too ravenous or aggressive. You may find that adding too hostile a dither fish to a tank has the reverse effect, and the very fish you want to encourage out becomes all too aware of the risk to its fins if it does emerge.
Common name: Rainbow Krib.
Scientific name: Pelvicachromis pulcher.
Origin: Nigeria, Cameroon, Benin.
Size: Male 12cm; female 8cm.
Notes: Widely available, though wild caught specimens rare.
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Nathan Hill reveals a fish thatâ€™s a symbol of sustainability, bringing hope and financial support to the very people who need it.
One definition of the word cardinal is: 'paramount, or of foremost importance'. For the indigenous peoples of the Rio Negro it’s patently clear just how important the Cardinal tetra really is.
This fish provides them with income without overexploiting natural reserves, which helps to retain the unspoilt nature of their homeland and cultural heritage.
The Cardinal tetra (Paracheirodon axelrodi) could be the most economically important ornamental fish on this planet. From South America, in a distribution that ebbs from Brazil across to Venezuela and Colombia, it is the staple fish that every hobbyist has seen and most will have kept.
For its novel appeal — and few freshwater fish have such a striking iridescence — there is a serious side to the Cardinal and that’s the topic of sustainability. As well as being a global aquarium favourite, the handling of the Cardinal represents an attainable ethical ideal; a perfect working example of how responsible fish collection can be performed. It’s not lightly that the supporters behind the Cardinal tetra trade bandy their optimistic slogan: 'Buy a fish, save a tree'.
Buying Cardinal tetras preserves foliage and peoples in those regions of South America where the fish proliferate.
Project Piaba, established in 1989 under the coordination of Ning Labbish Chao, has sought to refine, investigate and promote tetra harvesting for optimal benefit to the communities there.
Rather than shameless profiteering with exports, Chao has put into place a project that now sees financial benefits to a wider medley of individuals.
Later in the project’s life, financial injection from philanthropist Dr. Herbert Axelrod gave rise to the Dr. H R Axelrod Ornamental Fish Laboratory, which was further upgraded to the Centre for Aquatic Conservation.
Since then Piaba has provided education, scholarships for students, and promoted awareness of its cause.
Figures vary from source to source, but bolder claims cite numbers of up to 30 million fish exported annually from the Rio Negro and conservative estimates of up to 15,000,000 fish reflect the scale of the operations.
Paracheirodon axelrodi accounts for around 80% of these total exports. This in turn provides an income for roughly 60% of the riverine inhabitants of the Negro. Many families rely on it for their daily sustenance, but we aquarists so easily take it for granted.
There have been concerns over the impact of removing so many fish from the region, but on the grander scale of things the figures are small.
It is understood that billons of Cardinals perish each and every year due to the onset and subsequent decline of the rainy seasons. The Cardinal’s wildlife cycle could be considered closer to annual fish like killifish.
Any wild Cardinal reaching more than two years of age is considered a true veteran.
The benefits of distributing income from these fish are clear. It lessens the divide between rich and poor in a region where inequality could be rife. Moreover, it means indigenous peoples need not resort to alternative methods of generating income, such as ‘hack and slash’ tactics to destroy forestry to make way for short-term crop gains.
South America has been under the scrutiny of the affluent world for some time in its approach to razing huge areas to make fast gains on maize, cattle harvests or even contraband like cocaine. Projects like Piaba that serve to undermine the 'here today, gone tomorrow' strategies of aggressive farming, are pivotal in preserving large expanses of wilderness.
Without even realising it, money from Cardinals that you have purchased has likely trickled into the preservation of riverside regions or the rainforest.
Paracheirodon axelrodi is the original double-take fish. Even non-fishkeepers are hypnotised by its sharp, crisp markings and the way that the fish almost glows as though it has created itsown light.
The colours are attributed to iridiophores, and these, along with the cytoplasm and guanine layers in the fish’s skin, have long been subject to research.
Cardinals have a degree of control over their own colours, increasing the cytoplasm layer in their skin in the daytime, altering the refractive properties and, subsequently the wavelengths of light reflected. This is worth bearing in mind when buying some, because a retailer hates to be asked for 'six of the greener ones'. Given mere minutes, any markings may become very different.
In their natural range of the tannin-stained, rich-red rivers of the Rio Negro and Rio Orinoco, those colours serve as communication and predator deflectors. They are pretty, but a predator can find it hard to determine exactly where the fish is. Is the body actually in the water, or can it see the reflection of the fish bouncing from the underside of the water’s surface?
Pending region of capture, markings can fundamentally differ. Those from the Rio Orinoco have a blue stripe that reaches just short of the soft, fleshy adipose fin, while those from the Rio Negro have blue that extends beyond.
Orinoco fish also have wider red sections in the caudal peduncle. There are golden and silver-striped forms, rarely seen in the trade, as well as farmed colour morphs, mostly from the Czech Republic.
Come the night the colours change, with the red fading while the blue band alters to reflect more blue and UV light, contrasting their greener, daytime forms.
It’s understood that night time induces a shift in the spectral detection range of their corneas too, their eyes shifting wavelength so they can still see each other.Feeding and keeping
Cardinals are moderately easy to sustain, as testified by the endless thousands of community tanks that house them.
To see them at their best, recreate the wild environment. A tank of 80cm/31” or more works well for small shoals, though many keepers have housed them in tanks at 45cm/18” or less. A larger tank is preferable for relaxed fish and stronger shoaling inclinations.
Filtration need only generate light flow as these fish aren’t familiar with swirling torrents. I advise an internal canister or a small external filter connected to a spray bar to distribute weaker currents.
Lighting need not be intense, as the reflective nature of the fish will bounce off whatever is available. Low output T5 or even T8 tubes work wonders without bleaching the fish into the background.
Consider the kinds of branches and litter that would fall into slow moving Amazonian rivers or flooded forest canopies where the fish spend time during each flooded season.
Fine sands, wood tangles, mats of leaf litter, seed pods, some floating greenery and large doses of blackwater extract will create a home from home. If using external canisters, peat can be used in one of the chambers to release tannic and humic acid.
If that’s too environmentally unsound, or if you lack a canister, use almond leaves or alder cones to create those dark conditions that are so loved by Cardinals.
Cardinals are found alongside huge ranges of other fish in the wild, including hatchets, pencilfish, corydoras and loricariid catfish such as otocinclus, and a long list of other tetras, cichlids and more. Researching a Cardinal’s tank mates is part of the fun!
Keep temperatures higher, ideally at 28°C/82°F, although if this becomes prohibitive for the other fish they will tolerate much lower and may even start to breed when things cool to 24°C/75°F.
Feed a mix of dried and frozen foods, and live Daphnia when available. Wild morsels of choice include mesofauna — tiny bugs that occur naturally on leaf litter — and tiny insects and crustaceans. Colour-enhancing flakes work wonders at bringing out the red in the flanks.
The fish will also take a degree of algae food but generally swing to the carnivorous end of the omnivore spectrum.
Be vigilant with new purchases. As most are wild harvested, they can bring in unwanted pathogens.
Monitored exports have revealed fish that carry Gyrodactylus, Ichthyopthirius, Piscinoodinium, Procamallanus worms and the dreaded Neon tetra disease, Pleistophora. Be aware of the signs of any of these illnesses, and watch new arrivals like a hawk for the first fortnight: assuming you haven’t quarantined them first.
Despite being delicate in the aquarium, Cardinals withstand some conditions that no other fish can — particularly a level of acidity that would kill others.
In the wild, they’ll usually be found in waters with a pH value somewhere between 5.5 and 6.0. In extremes they have been recorded at 3.5pH, with zero-associated hardness — the pH of a typical orange. In tests it’s found that lethality starts to take its toll at 3.35pH.
This extreme tolerance is only possible in water-borne humic acid, which helps to reduce sodium loss in the fish. In typical acidosis it’s often the osmoregulatory effect of losing sodium that kills.
Many people misunderstand this acidic tolerance and have applied Cardinals to incredibly low pH tanks in absence of humic acids where they have perished. Although such low pH levels are tolerated, for most Cardinal keepers they are unnecessary and the fish will be happy at a pH value of 6.0 for its entire life.
The man behind the name (picture above by George Farmer)
It’s impossible to talk of the Cardinal without referring to Dr. Herbert R Axelrod — the person they’re named after and who has popularised the species.
A man simmering with character, Herbert has an ebullient history during which he advised Sir Winston Churchill on goldfish, collected alongside the Japanese emperor Hirohito, caught wild Amazonian beasts for Walt Disney, liaised with King Leopold III of Belgium and was invited by the then president of Brazil, Humberto Castelo Branco, to help draw up conservation plans for the Amazon.
As well as gaining degrees in physics, biology, mathematics and chemistry, Herbert also found the time to learn at least six languages, so it’s difficult to imagine how he found the opportunity to explore the world at the same time as establishing his huge publishing empire —which survives to this day.
Explore Herbert did, and he had a hand in introducing many new species of fish that carry his name. The echoes of 'axelrodi' and 'herbertaxelrodi' in the monikers of many varieties really bear testimony to Herbert’s aquatic doggedness.
Herbert came across the Cardinal in 1954, thinking the fish to be a new giant variant of the Neon tetra.
Returning with some to America, he noted that they behaved and spawned differently to classic Neons, and he sent some to Dr. Leonard P Schultz at the Smithsonian institute.
Leonard buzzed at the new fish. He pointed out that it was not just a new species but at the time belonged to a fresh genus separate from the Neon due to its different dentition.
Eventually in 1956 the fish was described and named Cheirodon axelrodi — later revised to Paracheirodon alongside Neons — in Herbert’s honour.
There was initially some professional friction because taxonomists Weitzman and Myers had also described this fish and they had called it Hyphessobrycon cardinalis.
Over the next 18 months debate raged until the International Commission of Zoological Nomenclature swung towards axelrodi.
On a few levels the 'discovery' of the Cardinal is far from undisputed. First of all, we know that South American natives were aware of these fish for millennia, so any claim to be the 'first' is hopelessly optimistic.
It transpires that the real Western 'discoverer' was most likely the limnological researcher Harold Sioli, who stumbled on them two years prior to Herbert in 1952. However, thinking they were a variety of Neon he made nothing of his find.
There are also reports of the fish being transported around South America by Captain Malm, a Brazilian pilot, who distributed but never described them or took the 'discovery' further.
Irrespective of who cast eyes on the Cardinal first, what remains undisputed is that Herbert was a pioneer who put them on the fishkeeping map.
Despite any disputes over discovery, it’s a happy outcome that the fish now supports communities, protects habitat and cultures, and pleases aquarists across the globe.
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Dave Wolfenden explains how slug and snail molluscs can make your reef tank a cleaner, happier place.
Gastropods, which includes slugs and snails, are a diverse group. They comprise some 40,000 species whose habits range from grazing herbivores to out-and-out predators.
Many can be usefully employed in the aquarium for their janitorial capabilities, primarily for their ability to graze away nuisance algae.
Correct identification of any can be tricky, however, and it’s important to determine the habits and size of any purchase to prevent nasty surprises.
This genus name is inspired by the shells’ resemblance to a turban. Many snails are sold generically as ‘turbo snails’, although the real deal refers to only a few specific gastropods, identifiable by their rounded shell shape and their operculum — a flap used to close off the aperture.
Overstocking is a common mistake when adding these to the aquarium. One per 50 l/11 gal is usually a sufficient ratio, as algal growth needs to be able to sustain any Turbo population.
Tectus and Trochus
These are also sold as the 'giant turbo', due to their resemblance, and larger ultimate size — some growing to more than 8cm/3.1” across. They usually have a smooth shell too.
Being large, overstocking is common as a surprising amount of algal growth is needed to sustain them. Aim for no more than one snail per 100 l/22 gal.
Frequently offered is the Banded trochus (Trochus histrio) from the Indo-Pacific, which is a good value and hardy grazer.
Snails of the Cerithium genus are often available as part of the reef aquarium’s janitorial crew and these cone-shaped molluscs are always an excellent choice because of their excellent grazing and scavenging abilities.
These hardy snails are also frequently sold as 'turbos' and handy on account of their small size, making them ideal for nano systems. Consider one snail per 25 l/5.5 gal. Astraea tecta is worth considering, if only because of its attractive pyramid-shaped shell.
The conches of the Strombidae family can greatly enhance the captive reef and some species can make short work of algae as well as consuming detritus in hard-to-reach places.
The Caribbean queen conch (Strombus gigas) grows to 30cm/12”, making it unsuitable for home aquaria. Instead, opt for one of the smaller sand-sifting conches (Strombus spp). These plough through the substrate, consuming detritus and filamentous algae, so provide a suitable sand bed.
These can make excellent grazers, although there are exceptions and research and positive species ID is essential. They’re characterised by highly polished shells, at least partially covered by the mollusc’s mantle during movement.
The most commonly kept species in the aquarium are the Money cowrie (Cypraea moneta) — pictured above — and the Ring cowrie (C. [Monetaria] annulus). Both of these Indo-Pacific creatures are small and make great janitors.
The Tiger cowrie (C. tigris) can be iffy. Characterised by its mottled brown and beige shell, this Indo-Pacific species grows to some 10cm/4”, depending on where it was collected. These can dislodge rockwork as they bumble around and, while useful scavengers, may also predate on sessile invertebrates. Anemones, soft corals and sponges can all be potential victims.
If it’s weird you want, how about one that looks like lettuce?
The sea hare is a completely different nudibranch. It is so called because of the ‘bunny ear’ appendages known as rhinophores and used for chemical detection.
Sea hares may use extensions of the mantle to swim, which is quite a sight.
Some species are challenging, due to specialised feeding requirements, but a few may be attempted by the dedicated.
For example, the Frilly sea hare (Elysia crispata, formerly known as Tridachia crispata) at up to 8cm/3.1” and from the Caribbean is a strict herbivore. It requires plenty of algae and mature live rock, but a specimen can be sustained in a reef aquarium.
This species has highly variable coloration, but it’s easy to see why adults are given the common name of Lettuce sea slug, thanks to the bizarre folded lobes adorning the mollusc’s body.
Several imported gastropods shouldn’t be contemplated by responsible marine aquarists. These include:
Even potentially deadly, they are sometimes seen in the trade and are not restricted under the UK’s Dangerous Wild Animal legislation.
Members of the Conus genus predate other animals, including fish and other molluscs. They may be inactive during the day, burying themselves in the substrate. However, at night, they emerge to stalk their prey.
With a touch as deft as a ninja warrior, they can ambush sleeping fish and other hapless victims, spearing them with a modified disposable radula linked to a poison glad. The poisons are known as conotoxins and among the most potent neurotoxins known to science.
You can recognise most members of the genus, thanks to their distinctive shell morphology, as it’s easy to see why they’re called cone shells.
The Geography cone (C. geographus) — pictured above — is from the Indo-West Pacific and grows to 10cm/4”, while the Literary cone (C. litteratus), up to 13cm/5.1” and from the Indo-Pacific, has distinctive brown spots on its yellow shell. The Textile cone (C. textile) growing to 10cm/4”, is also an Indo-Pacific species and has a beautiful shell, making it highly prized. Just don’t think about keeping one, as all are also venomous predators!
True sea slugs or nudibranchs (meaning ‘naked gills’) comprise some of the ocean’s most psychedelic animals and their stunning coloration betrays their toxicity to would-be predators.
In fact, their distasteful nature is often due to their ability to sequester (store) the stinging cells (cnidocytes) from their prey, such as corals and hydroids. The undischarged cells are known as kleptocnidae (‘stolen stings’) and can be deployed against any potential predator.
The aposematic (warning) coloration of nudibranchs seems universally recognised, as they are given a wide berth. Many species are tiny, but some range up to nearly 0.5m/1.6’ long.
Occasionally seen and quite expensive is the Spanish dancer (Hexabrachus sanguineus). This 40cm/16” creature has a wide distribution from the tropical Atlantic to the Indo-Pacific and there’s great coloration diversity among individuals.
Its common name is inspired by its habit of ‘dancing’ flamenco-style when swimming, courtesy of flapping actions of its mantle.
These are difficult to maintain, due to their diet of sponges — and this species is among the least fussy of nudibranchs. Incidentally, this plays host on the reef to the Emperor shrimp (Periclimines imperator), which hitches a ride as well as feeding on its mucus secretions.
While their beauty makes them highly desirable, feeding habits make nudibranchs a poor choice and responsible aquarists should avoid them.
Many species are obligate feeders of one particular prey species of coral or hydroid — in other words, they can only survive on that species and will starve if their natural diet is not provided.
Species ID is complicated and matching a nudibranch to its natural diet, plus providing adequate quantities of that diet, is beyond the realms of most.
Murexes (Murex spp.) are occasionally picked up by some unwitting reefkeepers who live to quickly regret their decision when this predatory snail has finished off other molluscs in the tank as well as tubeworms.
To be fair, it’s easy to see why murexes are so appealing, thanks to their bizarre shell shapes adorned with prominent spikes.
However, these fascinating and expensive gastropods are not suitable for most reef systems, although they can be successfully kept in a FOWLR (Fish Only With Live Rock) aquarium system with a few fish.
Never use any copper remedies
Gastropods are extremely sensitive to copper, so never subject them to copper-based medication — and grazers need to be introduced to systems with sufficient algal growth to prevent starvation.
Supplementary feeding may be necessary in certain cases.
Gently does it
Gastropods, as with all molluscs, fare badly if subjected to rapid changes in temperature and/or water chemistry. For this reason, take extra care and plenty of time when acclimatising them and use the drip method to ensure fine control when altering water parameters after transport.
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Neale Monks advises a PFK reader on the causes of "stunting" in the aquarium.
Q. I am aware that some species of fish produce a growth inhibiting hormone that can have marked effects in a densely stocked aquarium.
Is this hormone removed from the water by filtering it through carbon?
Peter Russell, email
A. You are correct that there is some evidence that chemicals produced by fish as they grow can suppress the growth of other fish of the same species in their immediate environment. This is primarily an issue for fish farmers, and I believe most of the evidence for this phenomenon comes from studies of cyprinids (such as carp) and salmonids (such as trout).
It's important to note that some fish clearly don't work this way, for example Tilapia (cichlids farmed as food) can grow to large sizes seemingly regardless of stocking density provided water quality is adequate. Aquarists will also be aware that catfish like plecs, Channel catfish and Iridescent catfish also seem to reach large sizes, even in overstocked tanks.
In any case, while chemicals produced by growing fish may be responsible for "stunting" under some circumstances, other factors may be at play as well. An overcrowded tank is an unhealthy environment, and unhealthy fish won't grow as well as healthy fish.
High nitrate levels for example are often characteristic of overstocked tanks, and even if not immediately toxic, nitrate does have an appreciable effect on the health of your fish. Fish grow continually through their lives, but they grow more quickly when young, so if kept in an aquarium that's too small for the first year or two, a fish may never reach its largest size no matter how well it's kept thereafter.
You can often see this with Clown loaches, a species that rarely reaches its full size in captivity because so few people keep them in adequately large aquaria as youngsters, let alone as adults.
So while (fresh) carbon should remove hormones from the water, aquarium size and water changes are factors that affect nitrate level. If you want a fish to reach its full potential, the key thing is to keep it in a clean, spacious tank, and not to rely on chemical media to remove dissolved metabolites or hormones.
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Dave Wolfenden offers advice for a reader who's having a turf war in his reef tank.
Q. I was wondering you might be able to offer some help with controlling an algae outbreak in my aquarium. The algae seems to grow from the coraline algae and is a very dark green, wiry and hard grass-like algae. It requires a bit of force to remove it.
My parameters are: NH3 nil, N02 nil, N03 <5ppm, Phosphate nil, pH 8, KH 10°, calcium 420ppm, sg. 1.026, temperature 25°C/77°F — done using API tests except pH (Salifert).
Lighting is TMC AquaBeams with white and blue LEDS mixed on each strip, controlled at 70-75% with the TMC controller. Lights are on fade from 10am till 12noon, on fully til 6pm and fade off by 8pm.
For filtration I'm running two powerheads, V2 400 skimmer, Fluval 306 with just Rowaphos and Purigen which is replaced monthly. The tank is 125 l/27 gal and has 25% water changes weekly.
Stock is a False clown, Yellow goby, Sixline wrasse, Coral beauty, two Yellow-tailed blue damsels and a Red Scooter Blenny, along with a green Bubble anemone, a Knobbly toadstool coral, Jasmine coral, plus colonies of Zoanthus and Blue mushrooms, two feather dusters, hermits, Turbos and a Cleaner shrimp. There’s 12kg of live rock in the tank.
The issue probably began way over a year ago when I was running standard fluorescent bulbs. But now I'm considering a larger upgrade so I would like to figure a way of controlling it or beating it if possible. Can you help?
A. From your description, I’d suggest that this might be a species of Cladophora, which also answers to the name of 'brush alga'. It’s quite tough stuff, and as you’ve discovered it’s pretty resilient too. It commonly ‘hitch hikes’ on live rock, and can appear many months after the rock is introduced. There are two approaches to controlling algae — limiting nutrient input and removal — either manually or through biological agents.
Manual removal can help to an extent, but the algae will simply grow back. Not many herbivores touch these wiry algae, and your choice is limited anyway due to the size of your system and its existing inhabitants. A tang isn’t an option as even a small specimen needs much more room. An Emerald crab (Mithraculus sculptus) might eat it, but these can be quite aggressive and cause their own problems.
On balance, I’d suggest that you concentrate on limiting nutrients, specifically nitrate and phosphate, to put the squeeze on this unwanted visitor. Although your readings for both phosphate and nitrate look fine, here’s the thing: there may be unacceptable amounts of these algal fertilisers being generated in the system, but the algae is actually assimilating them, meaning they are not being detected by your test kit.
Review feed input to the system, and make sure that excess food is not being added. Washing frozen feeds to get rid of residue can be useful to limit nutrient input. Ensure that the skimmer is functioning optimally, and give the tank’s substrate a really good clean on a regular basis.
Although you’re already performing 25% water changes weekly, I’d suggest increasing the frequency of these to twice a week, and if you’re not already using RO water, then seriously consider it.
It might be worth thinking about upping the tank’s mechanical filtration, and — if it’s not the case already — part of your external filter could incorporate a mechanical sponge, which should be frequently rinsed in tap water to prevent build up of detritus, and to stop the media from becoming a biological filter (which may contribute to high nitrate levels).
Algal issues arise due to an excess of nutrients, and by reducing the input of these (and ensuring their swift removal from the system) it is possible to curb the problem — in time...
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Dave Hulse offers advice to a PFK reader whose goldfish is experiencing buoyancy problems.
Q. I have two Ryukins in a 200 l/44 gal tank. One of them has started to have trouble swimming and I think it must be something to do with his swimbladder.
Sometimes it’s OK and swims around normally, but it seems worse in the evenings, after feeding, when he seems to have trouble staying the right way up.
I give the fish flake and pellet food for goldfish. The water conditions are all testing OK and at the moment the other fish seems to be fine.
J. Davies, email
A. Ryukins, like some other fancy goldfish varieties, are especially susceptible to these kinds of problems, as their fancy body form contorts the spine and internal organs, placing greater pressure on the swimbladder.
Also as the fish takes extruded pellet or flake food from the water surface, it gasps in air which can enter the swimbladder, again causing buoyancy problems.
It does sound as though this problem is due to excessive air intake during feeding, especially as your fish seem to be otherwise OK.
Feed a quality sinking pellets food to minimise air intake and offer bloodworm and similar 'wet' foods on a regular basis. Bloodworms help by encouraging the passage of food through the intestine, which can dislodge any blockages that might lead to swimbladder problems.
Fasting your fish for a couple of days may also help.
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Dave Woldenden has some advice for a reefkeeper who's been inspired by a recent holiday.
Q. A recent holiday to the Red Sea has inspired me to set up an aquarium hosting corals and fish from that area. I have some experience of keeping marine fish and invertebrates, and plan on using a 580 l/128 gal tank. What can you suggest as suitable inhabitants?
Ray Burns, Portsmouth
A. This sounds like a great idea for a themed aquarium, and there are plenty of possibilities. Lots of fish and invertebrates in the trade occur in the Red Sea, although obtaining specifically endemic species could be pretty expensive, and you’ll need some luck getting hold of some of the more specialised animals.
For me, the quintessential Red Sea fish would be the readily-available wreckfish Pseudanthias squamipinnis, and I’d base a biotope around this fish if you’re after a really authentic Red Sea look — you’ll certainly have enough room for a great aquascape.
Instead of constructing a wall of rock at the back of the tank, I’d create a fairly extensive sand zone, with substrates varying from fine sand to larger chunks of rubble. Dominating the sand zone, I’d build up a live rock coral 'head' (or 'bommie') – some creative use of cable ties, PVC pipes and epoxy resin can yield something more interesting than a mere stack of rocks.
This hardscaping can form the focal point of the system, and may be used to house, for example SPS corals such as Bird’s nest coral (Seriatopora hystrix) and Cauliflower coral (Pocillopora verrucosa), both of which are common in the Red Sea. These are quite demanding, however, and as an alternative soft corals such as pulsing Heteroxenia fuscescens (pictured above by Derek Keats, Creative Commons), Anthelia or Sarcophyton might be more to your liking — as well as being more forgiving.
You could keep a shoal of six or so wreckfish, but make sure the group contains only one male (sexing is easy, with males having an elongated third dorsal fin ray and a more intense purple coloration). Other fish of note include the Orchid dottyback (Pseudochromis fridmani), a Red Sea endemic, and Purple tang (Zebrasoma xanthurum).
If you’re interested in clownfish, then you’d really have to look at seeking out a pair of the endemic Red Sea clownfish (Amphiprion bicinctus) and if you can maintain optimal water quality, a Bubble tip anemone (Entacmaea quadricolor) placed on the coral head would provide an ideal home.
There are plenty of other possibilities, but that’s my suggestion. Personally, I think it’s an opportunity to create something really different, and rather than go crazy with a 'pick and mix' approach, judicious selection of a few species will yield results. As they say, sometimes less is more...
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Nothing seems to compare to the fearless Mantis shrimp. It has the brains and weaponry to make it the most special of agents, as Nathan Hill explains...
If humanity destroys itself tomorrow who takes over the world? Rats? Cockroaches? I’d hazard that the seas would become the domain of the Mantis shrimps.
Mantids are natural-born record breakers and perfect examples of niche adaptations thrown up through evolution. They have probably the best eyes in the world and an explosive, superhuman punch.
Despite the name, Mantis shrimps are not shrimps at all; there’s little 'prawny' about them, despite their shared crustacean origins. They look like a cross between the secret lovechild of a praying mantis — from where they derive the mantid part of their name — and a lobster, and the front of the former seems to have been grafted to the rear of the latter.
There are some 400 species of Mantis shrimp too, ranging from midgets of just a few centimetres to beasts longer than a man’s forearm,
There are two ways by which you’re likely to meet one in an aquarium; deliberate purchase, or accidental addition via live rock. Their survival skills are up there with Bear Grylls.
Unceremoniously uprooted with a piece of rock, packaged in a dry box, subject to changes of temperature, and exposed to horrendous water in a curing tank — mantids have frequently endured all of that without so much as a shrug.
Get one in your tank and it will start to make a dinner platter of the other inhabitants — but removing such a stowaway Mantis can be a challenge as they move fast to secrete themselves away in a cave at the first hint of danger.
The first sign of their presence may be some mutilated fish and inverts, so get searching for their rock of residence.
Given how many aquarists are mantid fans as projects in their own right, that might be all you need to do. Simply stick them and their rock in another tank and you’ll have a free, fascinating pet — plus it’s a perfect excuse to get another aquarium in the house!
Smash and grab
It’s impossible to talk of a Mantis shrimp without referring to its weapons of mass destruction, in the form of raptorial appendages — either being a spearer/grabber (pictured above with its long, hinged arms) or a smasher (pictured below, showing off one of his toughened, high speed hammers). These either lunge and spear prey or deliver a devastating hammer blow that stuns and physically shatters their opponents.
Size for size, smashers have the most powerful 'punch' of any creature. Although their clubs have the acceleration of a .22 rifle bullet, they don’t have the velocity, but this isn’t to undermine their power. The speed of a smasher’s club is around 20m/66’ a second, or 45mph, and this can result in prey receiving a right old belt of up to 1,500 Newtons.
These clubs even lower the pressure of the water ahead of them, causing it to vaporise and cavitate. In a moment this cavitation collapses, releasing a second burst of energy of up to another 590 Newtons against the prey. This creates not only heat and an audible sound but also a momentary explosion of light. When a Mantis strikes, its hapless victim literally sees stars!
The punch is driven by a muscle and lock mechanism inside the arm that causes huge amounts of energy to be retained. Once withdrawn, the whole arm is tensed and ready to shoot forward, much like a crossbow. All the Mantis need do is release the lock!
Just prior to moulting, a Mantis gets volatile, smashing everything in range. Yet for a short period over the moulting cycle it is helpless, and instead resorts to bluffing, waving its arms and showing two colourful patches directly connected to its strike power.
It’s thought that this behaviour fools rival mantids into thinking it’s still fighting fit.
Shields at dawn
The tail of a Mantis is surely an armoured work of art.
Impact resistant, the chemical structure of their telsons has long been analysed and military intelligence sources in particular want to know more about what makes them so tough.
When two smashers meet they may go tail on, exposing only this hardy part to their foe which will smash against it. In return the other smashes back. Such fights are often just ritualistic and may result in both shrimps retreating.
However, in the event of one clubber invading another’s cave or burrow, this tail is the first line of defence to block attempts at entry.
During their reproductive phases, mantids fluoresce to show their receptiveness. It’s easy to seek suitable partners when their bright patches are shining.
Eyes that see so much more
Mantis eyes are extraordinary. While humans have three colour receptors a Mantis shrimp can have up to 16 of them.
Having 11 or 12 of those receptors devoted to colours, they see the world in a far wider spectrum than we could ever hope to imagine, including way up into the infrared and down into the ultraviolet wavelengths.
There are also colour filters and even polarization receptors so, unlike any other animal, Mantis shrimp can see polarised light and the reasoning behind this may well be down to breeding or other means of communication.
The ability to display in polarising light means that mantids can potentially make contact with each other without the risk of revealing themselves to other predators.
This ability to communicate in colour could also be pretty essential for these shrimps when they begin to seek out a mate.
Though the two eyes appear on stalks, they are comprised of 10,000 individually processed ommatidia, so not only do they have independent vision at the top of each stalk but the very shape and curvature of each eye enables depth perception. They can therefore focus on several objects at once.
Mantids also have an acute sense of smell, combined with an ability to learn fast.
When a Mantis first meets an octopus, for example, a fight will ensue. After that it remembers what an octopus smells like and when it comes across a burrow with octopus aroma, it will instantly tense up, assume a battle stance and enter cautiously.
These creatures have no fear of the high toxic Blue Ring octopus, clubbing it until the venom sac ruptures and the danger of being poisoned passes as it dissipates into the water.
Whether they map their neighbourhoods visually or through smell isn’t fully understood, but we do know that when a Mantis sets up a home it learns its surroundings intimately and can find its way about with ease.
Can I keep them?
You’ll need to keep this shrimp solo and set up a tank specifically for it. Other moving inverts will be bludgeoned, fish minced and sessile inverts and corals knocked over.
This is a creature destined for a sandy, rocky tank, imitating its natural range.
The likeliest offering you’ll come across is the Peacock mantis (Odontodactylus scyllarus). These brightly coloured, highly intelligent pets are both long lived and reach a reasonable 18cm/7”, so although a huge tank is not essential it’s better to provide one if keeping a Mantis long term.
Given that some species live longer than 20 years, and typically Peacock keepers report seven to ten years, it’s an inhabitant you’ll be looking after for quite a while.
Provide a tank of around 120cm/4’ long, and offer a thick, sandy substrate as mantids are burrowers and will freak out in a bare tank. Add a few pieces of live rock and it will excavate a cave for itself in next to no time.
Keep lighting low and high-intensity LEDs or metal halides are not needed. Even a single T8 tube will provide all that’s necessary.
Feeding is a doddle but if done badly is dangerous, as can be the case with maintenance. It’s not for nothing that these creatures are nicknamed 'the thumb splitters'.
Never try to hand feed. Even tongs and tweezers can be knocked clean from your fingers, broken, or snatched and carried back to their lair. Mantis are fast and indiscriminate and can easily tear flesh and crack fingernails in two.
Peacocks have little fear of novel objects and when you change water, they will approach to investigate. Always know exactly where your Mantis is when you work on the tank — as it’ll know exactly where you are!
Aside that, their requirements are minimal. Feeding can involve any snails, shrimp, squid and pieces of fish, which they will take greedily. Don’t overfeed them and once every few days is adequate.
Run the Mantis tank as you would a FOWLR system, using a good skimmer — given their rich, meaty diet — and external or sump filtration.
Although they have no particular water needs, mantids won’t do well in poor water quality and can succumb in polluted conditions.
Tease them at your peril!
There are a few reports of large smashers breaking aquarium glass and it is a real, if low likelihood hazard.
They like to strike at anything, so if you happen to be on the other side of the glass, teasing them with a shiny key or food, don’t be too surprised if they dispose of the pane to get to it.
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Do your dreams of broad-beaked bottom dwellers come to nought? Most are too big for a life behind glass, but Nathan Hill finds a smaller specimen that might just 'fit the bill'.
The freshwater habitats of South America are amongst the most diverse and heavily life-fortified of any on the planet. Little wonder, then, that from time to time they should throw up curios and novelties that catch our attention.
Shovelnosed, or Duck-billed catfish of the Amazon are moderately well known, at least from a gourmet point of view. This subset of chunky, heavyweight pimelodids makes up a large portion of the fish marketed for tables on the South American continent, and why not? They are abundant, adaptable, and have even managed to encroach new territories on the back of damming activity.
For the aquarist, many shovelnoses are an unrealistic and fanciful dream. With sizes scaling up into the realms of several feet, the tank or pond sizes required to keep one of these 'big cats' is prohibitive, especially in price.
Sorubim lima, the classic or original shovelnose, sits on the fringe of the beaked collective, and keeping it confined to glass is not only feasible, but realistic, as long as liberties aren’t taken.
Lord love a duck!
They are fast growing fish, so any attempt to house them must be committed from the offset. Though final adult size is contested – somewhere between 30/12” and 55cm/22” for a tank bound specimen – the galloping rate at which they get there is not. As a rule, it is less than usual for a lima to take over two and a half to three years of its predicted ten-year lifespan to stampede to full size.
The notion of small tanks acting as some organic pace car, slowing this growth rate down, is flawed, and attempts to keep these fish confined to tiny spaces will lead to stunted growth, and grossly overloaded biofilters. A fish that can weigh in at 1.3kg fully grown eats a lot, and what goes in one end…
There are five species in the Sorubim genus, though four of these are rarer than S. lima in making an appearance, or at the least being correctly identified and sold under the right name.
In its natural range, wide across the Amazon, and featuring in the Orinoco, Tocantins, Parnaiba and Parana basins (the last of which it has been helped to colonise through damming) S. lima overlaps some other species in its own genus, not just sympatrically, but syntopically.
Given that S. lima and S. elongatus are frequently found together, as are S. lima and S. maniradii, it would be more surprising if some of these other types had not made their way into the trade through accidental channels.
Across their conquered expanse, S. lima prefer to live in lowland regions, and are found in both lotic (river) and lentic (lake) environments, though they hands-down favour the former.
Ducks in the water
S. lima aren’t afraid of a little water movement when adult, and finding them in churning, fast flowing whitewaters is commonplace. Here, they dwell over a clay or mud substrate, becoming more active at night, and spending the daytime sequestered amongst the shadows of rocks, or hunkered down within a tangle of fallen branches or tree roots. When recreating a tank environment, though clay is impractical, a soft, fine substrate should be considered.
Temperature in their range varies seasonally between 23 and 30°C, though a constant anywhere between is fine for aquarium care. Typical pH at points of capture will be sat between extremes of 6.0 and 7.8pH, though neutral to slightly acidic conditions are favoured. Hardness needn’t be high, and anything up to and including 18°dH is tolerated, though lower is better. Oxygen should be exorbitant, to replicate those whitewater conditions, and dissolved pollutants need to be low.
Sorubim fare badly with any levels of ammonia or nitrite, and even nitrate levels above 20ppm can lead to the fish producing excessive amounts of mucous that then visibly slough off from the body. This is a warning sign to look out for, and always indicates something amiss in chemistry or quality of water.
Tankmates and feeding are open to some debate. Some keepers have got on well with a host of species alongside S. lima, while others report shy cats that are bullied away and become emaciated.
It’s a no-brainer that particularly aggressive fish like larger cichlids will intimidate most fish, though it’s also worth avoiding other night active species that are particularly outgoing.
Sorubim prefer to feed in subdued lighting, though long-term captives tend to feed at any time of day. In fact, a darker tank all round is suggested, and a perfect excuse to put an old T8 to use. Combined with tangles of wood and reasonable flow, this will create a home from home.
Feeding the ducks (Picture above by Sitron, Creative Commons)
Adults are out and out piscivores, and fish in the diet will never be turned down. Though our American counterparts are fond of using live goldfish, there are health ramifications, as well as legal ones in the UK. Besides which, live feeding with fish is entirely unnecessary.
Chunks of white and oily fish (this latter being messy, and only used sparingly) can be offered alongside other meaty goodies like prawns, squid, earthworm and bloodworm.
Juveniles prefer to focus on aquatic invertebrates and insect prey, moving on to eating fish when they hit 10cm/4” or so. If weaned from young, then it’s likely a Sorubim will even take multiple forms of dry food, and watching them quaff down all sorts of tablets and pellets over the years leaves me in no doubt to their ease of feeding.
Adults only need infrequent feeds, once every two or three days. They are not creatures of habit, and will happily go for staggered periods between chow.
When young, Sorubim cluster together in large numbers and take to living in thick beds of deep grasses, where they spend most of their time upright.
Given their superb camouflage at this point in life – their elongate black caudal lobes and whiskers making them look just like dead vegetation – it’s not clear whether their upright behaviour is defensive, or one of an ambush predator, or, most likely, both.
At this stage, they fill up on insects, crustaceans and other inverts, only emerging from the foliage as they switch to a fishy diet. However, a part of that ‘upright’ behaviour seems to stay with them, and they often headstand as adults.
The latin name, like so many with fish, simply derives from the local vernacular for Pimelodid type catfish. With indigenous peoples calling all such cats Sorubi, it didn’t take long for taxonomists to latch on to it…
Why the long face?
Sorubim are instantly recognisable by that long, handsome proboscis, hanging from the front end like Popeye’s Alice the Goon.
Underneath resides a true cave of a mouth, ever hungry for any fish that can fit inside. The 'lima' part of their name actually translates as ‘file’ in reference to the abrasive inside surface of that gape, filled as it is with tiny, villiform teeth.
The snout is reportedly used to grub around in substrates to flush out prey, though this behaviour seems to be held back in most aquaria.
Like many catfish, it’s noted that Sorubim have weak electrodecetion abilities, and that shovel is peppered with ampullary sensors, such as those sharks and rays carry.
Combined with the vast, antennae like whiskers, these cats are well equipped to hunt down prey.
Don’t duck out!
The final issue to be addressed if planning a lima of your own is the size of their home. These are social fish that prefer to be in small groups, and that equates to an increase in the size required. Seeing a solitary 30cm/12” specimen in a 120cm/48” tank is a sorry sight, even if the fish is relatively day-dormant.
For a group of three, I’d be considering a tank of around 300cm/10’ in length, with a width of 90cm/3’. Depth should be considered too, given their periodic headstanding antics. Anything over 50cm/20” should accommodate this reasonably.
As a parting thought, do consider the long term care of your Shovelnose. As hard as it is to anticipate what tomorrow might hold, if you’re in any doubts about economic stability, then maybe avoid them. If you find yourself unable to house one anymore, you’ll find both retailers and public aquaria unsympathetic. As for selling one on at adult or semi adult size – forget about it!
Syntopic v. sympatric
Sympatric fish are those that simply share a particular river, pond, lake, and so on, maybe passing each other by every now and then, or never meeting eye to eye, with one at the surface and one at the base.
Syntopic fish tend to live in exactly the same niche, so if a sand-dwelling riverbank inhabitant shares that exact territory with another species, the two are syntopic (as well as sympatric).
See some of the other articles in this series:
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Not all butterflies flit gently. Nathan Hill homes in on a bizarre waterborne namesake that moves with lightning reactions.
Beneath the surface of still waters a wide, wedge-shaped brown fish hangs motionless. It views the world above and below with diligence, ready to pounce on food or launch itself like a missile at the first hint of trouble.
This is the Butterfly fish (Pantodon buchholzi) and a common sight in any store professing to know anything about curiosities. Its ease of keeping makes it popular with outlets catering for beginners.
At first glance it’s hard to work out which way the fish is pointing. In some cases, newcomers may fail to identify it as a fish at all.
Different league (picture by Isidro Martínez, Creative Commons)
Two anatomical features put Pantodon in a different league: the pectoral fins and the eyes.
From above, massive and triangulated pectorals look more aerodynamic than hydrodynamic, hence the fish’s common name. The fins look beyond sensible proportion, but this is not recent evolution, Butterflies being examples of older teleost fishes.
The fins are part camouflage, part escape route. Spread wide they emulate fallen foliage and with graceful movements the fish can saunter without giving their position away to potential predators or prey.
However, in times of crisis those fins can become ailerons as the fish launches from the water, rising as much as twice its own body length high, before linear flight brings it down and away from the danger.
The pectorals do the catapulting, while most other fish use their caudal fin — the tail — as the main driver.
The eyes are possibly even more spectacular.The internal configuration is genius and, had this fish been created by man, it would have been a combination of Japanese innovation and German engineering.
Pantodon have simultaneous air and water vision. With multiple retinal hemispheres in the eye, a dedicated portion of the visual angle is directed upwards, scanning for insects. Part of the eye is dedicated to viewing straight into the water column and a third section views predators below in a most remarkable way.
Rather than dedicate some of the eye downwards, as in the case of the Four-eyed fish (Anableps anableps), the Butterfly has a further region of retina directed to the water’s surface at such an angle that it views a reflection of what is beneath it. It makes a mirror of the very water it is looking out of.
Pantodon have evolved extra neurons and pathways in the brain to cater for this remarkable ability and such clusters of neurons are unknown in any other fish species.
These eyes, combined with those impressive launching abilities, combine with a response time to danger that we humans can only imagine.
The fish will register a hazard within five milliseconds (ms). Just ten ms later its fins respond, giving a total reflex time of 15ms. A typical human eye blasted with a puff of air generally takes 30-50ms before the stimulus registers.
This fish has also developed a kind of mechanoreception, currently known in only one other surface-feeding predator.
A Butterfly can detect the distance of prey hitting the water’s surface with pinpoint accuracy. If an insect touches the top of its aquaria anywhere between 5-20cm/2-8” away, it can lunge that exact distance.
It does so with detection performed by the lateral line, and the first few waves in a train that reach it are enough to give a location. This mechanism stays active at night, and in the aquarium they manoeuvre in the dark towards droplets of water.
Pantodon can be tricked in a laboratory by producing wave frequencies from a surface probe that represent a different distance of a falling object. The fish will base its strike distance on the information received and not the location of the probe.
Pantodon have almost stopped evolving. Scientists revealed that two geographically separated populations split over 57 million years ago and since then had indulged in no change to their phenotypes —the physical body.
It would appear that whether isolated in the Niger basin or the Congo basin, there’s no further requirement to tweak the body to fit in any more successfully.
However their genotypes – the gene sequences – have been subject to massive change, totaling nearly a 15% difference in their mitochondrial genomes.
By organism standards this is huge, and it’s not yet known whether the two populations can actually interbreed. Scientists generally say ‘no’ but anecdotal evidence may hint at the contrary.
Taxonomically, Pantodon buchholzi was always the outsider, with only one species found within its solitary genus. From a categorisation perspective, this is quite the Duck-billed platypus.
These fish can even breathe atmospheric air, expelling and gasping in one sudden movement. Unlike some fish that pass air through a vascularised stomach, Pantodon breathe through their swimbladders, having to exhale exhaust gases. These breaths will take place typically at around 10-30 times every hour.
Atmospheric breathing is a problem for domestic aquarists, increasing opportunities for airborne toxins to enter the fish as well as compounding issues in cold environments.
Pantodon aren’t fans of cold air and a chilly fish house with lukewarm aquaria but an arctic atmosphere can spell trouble.
How to set up home for an oddball of your own
Butterflies are among the easiest oddballs to keep, and setting up a harmonious tank is a project that every inquisitive aquarist should try at some stage.
Found from a range of waters over Cameroon, Gabon, Nigeria, Sierra Leone, Benin, and the Democratic Republic of Congo, their typical habitat will often be generic, although those fish they share their homes with may vary from place to place.
These fish inhabit either very slow moving or static waters, sometimes with abundant surface cover and sometimes with sparse. Decoration and planting is not critical, as they are far more concerned with what happens above the surface than beneath it.
Even if the fish pay no attention, a biotope can still be effective and décor should be steered toward a riverbank with steep inclines, tangled wood and plenty of vegetation.
Anubias species make good choices, as do Crinum natans and Bolbitis plants. Floating plants should be considered, although true African species are rarely seen in the hobby. Opt for some invasive Salvinia and keep surface movement minimal to see Pantodon at their most natural.
Pantodon like substrates to be dark. Coloured gravels are anathema to them and shouldn’t be considered.
Lighting should be dull. Pantodon are crepuscular fish, tending to do nothing when the sun is intense. In a bright tank they will usually stay dormant for long periods, so shading and an abundance of floating plants will help to increase roaming.
Given that bright lights are out, garish tank mates are redundant in the Butterfly tank. Congo tetras are often used, as are Brycinus longipinnis and Micralestes tetra, but the range can be so much more interesting. More fascinating companions can include elephant-nose mormyrids, African knifefishes, Ctenopoma species, and smaller, docile Synodontis catfish.
Small tetra and shrimp are not viable. Pantodon mouths are upward-slanting black holes, capable of fitting in astonishingly big fish and a brave tetra or a shrimp venturing high in the water will be consumed.
Pantodon are not critical of temperature, sitting cosy between 23-30°C/73-86°F. They like water soft and slightly acidic, but not the hostile and corrosive levels of some tetra: 6.2 to 7.2 pH keeps them happy and they approve of tannins.
They don’t get too big, reaching a maximum 12cm/4.7” in length, so a tank of 60cm/24” or more for one for much of its life is fine.
Sexing is easy, but breeding less so. Gender is identified by the shape of the rear edge of the anal fin. In females this is straight, but males are more convex in shape.
Males have a unique copulatory organ with folded structures in pouches covered by a bony plate. After chasing the female, he positions himself above her. Fertilisation is believed to be internal and eggs laid into the water. These clear, floating offspring rapidly turn dark and the female may produce them over several days — and up to 100 eggs per day.
The fry are difficult to raise, initially requiring tiny infusoria. Producing the food isn’t a problem, but getting it in the right place is. Unless it’s at the surface, the fry won’t be interested.
The fry should be removed, lest the parents eat them.
There’s no need to wean adult Pantodon on to dried foods, as they will take them from the offset. However, ensure any food remains on the surface as these fish will not drop into the water column to fetch it. Insects are taken without a thought.
Anything is accepted, with flies, spiders, woodlice and beetles all going smoothly down the hatch.
A true flyer? (picture by Toniher, Creative Commons)
Some scientists believe Pantodon is capable of more powered flight, given the anatomy of the muscles on the trunk and the connections to the pectorals.
However, as much as the fish may kink mid-glide, and though the fins may be tilted and twisted to aim, this cannot be considered flying in the true powered sense.
See some of the other articles in this series:
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Bob Mehen offers advice for a reader with a group of Clown loaches that are growing well - with the exception of one, which hasn't grown at all...
Q. About 12-18 months ago, I bought five very small (2.5cm/1") Clown loaches.
Four of them are now 7-8cm/2.75-3.25" — but the other one hasn’t grown!
All five are very healthy and look immaculate. There’s no sign of bullying, in fact the tiny one seems extra-happy — he’s out most of the time and schools with my five Chain loaches.
The other Clown loaches do school together but spend time hiding away, which I know is normal.
I’ve almost 50 years' experience of fishkeeping and have never come across this before in a fish that would normally reach such large proportions, meaning the relatively small size is so obvious.
If all five Clowns were tiny, I’d presume there was something wrong. But this doesn’t make sense.
Other stock includes eight Red-line torpedo barbs (around 10cm/4" long) four Marbled hatchets, a Snowball plec (I've had this for about five years) two 10cm/4" Pearl gouramis, a 15cm/6" Bristlenose (also about five years old) and the usual selection of Neons, Rummy noses, Corydoras and so on.
The tank is 260 l/57 gal and has been running about five years. It’s well-planted and I’ve had no deaths in the last year. The fish are fed a wide range of dried foods. I change about 80 l/18 gal of water every 2-3 weeks.
A. There are a number of reasons that could explain why one of your Clown loaches is remaining small, while its companions grow.
These are social fish and soon establish a rigid pecking order usually with a large, dominant female at the top, and the smallest male at the bottom.
It is possible that in your small group this smallest fish is unable to get the food it requires and its growth is suffering as a result.
Clown loaches are largely nocturnal so you may not be witnessing this behaviour as it is occurring after the lights are out. This could also explain this small loach's active daytime behaviour as it searches for food away from the larger sleeping fish.
Larger groups usually help spread out any bullying and allow all the fish to get their share, but this isn’t possible in your tank. These fish can easily top 12"/30cm and at that size need a tank considerably larger than your current one – 1.8m x 60 x 60cm/6'x2'x2' or larger is usually recommended for a group long term.
While your other Clowns have certainly grown since introduction I would expect them to be bigger than 7cm/2.75" by now. While they take many years to reach their full adult size, early growth should be rapid and I’d expect them to be nearer 10-15cm/4-6" each if conditions were ideal. Your stock levels do appear high for the tank's volume and stunting and its associated health problems could already be an issue for these fish.
It’s also possible this small fish is simply a 'runt' and despite your best efforts will never match the growth rates of the others or perhaps is suffering from a gut parasite infestation, but your reports of its general good health and vigour make this seem less likely.
Diet could also be a contributory factor – adding a selection of fresh and frozen foods such as bloodworm, brine shrimp, cucumber and blanched peas to supplement your current choices will be beneficial.
However, in the long term these fish simply need a bigger tank and if this isn’t feasible they’re probably best re-homed.
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