How’s the learning curve coming along for you? Nathan Hill looks at some of the most common blunders made by aquarists — both new and experienced!
I’ve kept fish for 35 years now, and every week I learn something new. The worst mistake any of us can make is to think that we know it all, and that we have nothing further to pick up.
For some of us the curve is gentle. For others, it’s a hairpin, leading to costly mistakes, dead fish, and frustration. Some aquarists may find themselves snarled up against a problem that requires thorough investigation. But there are also folks who are doomed to make life hard by overlooking some simple, easy to rectify measure.
Here’s a breakdown of some of the most obvious blunders and gaffs that fishkeepers — both old and new — are prone to making. Avoid them at all costs...
Imagine I trap you in a bathtub, but don’t let you out to use the toilet. The more I feed you, the sooner that bathtub’s going to turn foul. It’s just the same with fish.
Unless you’ve a demanding predator, then your fish (and your filters) will benefit most from small, regular feeds instead of big, random splurges.
Offer a little bit of food and see if they can eat it all in 30 seconds. If they nail it all in ten seconds, you’re not adding enough. If it takes them a minute, you’re adding too much. The trick is to find that magical quantity that will allow a 30-second feed at a time, and then add that amount three times in a row, allowing for a 90-second feeding time in total. Remove any uneaten food afterwards with a net.
I’ve spent enough time curled up with stomach cramps to learn this one for all of us. Do not suck hoses to start syphons. You’ll get ill. It’s that simple.
So how do you start a syphon? Consider buying a gravel cleaner with a non-return valve in it. That way, you just bounce the device up and down in the tank, and the water will flow out for you. Alternatively, get a model with a hand-powered pump to start it. Or splash out and get a battery powered model to start the water movement off for you.
Just do not suck on the end of a pipe, I implore you.
Mistaking pollution for disease
Most of us are savvy about this, but some people still refuse to accept that they might be directly responsible for the problems in their fish.
Water issues and illnesses go hand in hand, and it’s rare for aquarium fish to go down with disease if there’s no pressing issue of water quality. The symptoms of the two camps look very similar. Gasping, lethargy, dashing, slimy skin, cloudy eyes, poor colour — all of these are more likely to be the result of pollutants than pathogens.
Test first, reach for the medicines later.
Having shoals that are too small
Some fish are destined to do badly by virtue of being constantly nervous. Shoaling fish are gregarious by nature, and their whole life cycle may depend on their interactions with others.
In the wild, barbs and tetras may live in shoals of hundreds at a time. In those shoals will be complex hierarchies, social ties and breeding opportunities. When kept as three individuals in a tank, all of this innate social programming is redundant.
That could mean shy fish, hidden away, refusing to eat and slowly starving. Or in the case of others it may lead to fin nipping, as fish try to interact with different species as they would their own kind.
Always buy as many of one kind of shoaling fish as you can afford or accommodate. Mixed shoals, and the pick-and-mix option might be great for bags of Haribo, but this approach won’t work with sensitive animals.
Trapping sand and gravel in algae pads
I’ve seen acrylic tanks reduced to tatters in seconds, simply through the use of a badly maintained algae pad.
A piece of grit or gravel is like a diamond cutter once you start rubbing it against the front pane, so make sure you check your pad before and after each use. Rinsing beforehand is essential, and inspect closely. It may sound excessive, but when you’re cursing that 20cm/8in gash in the front of your tank, you’ll understand why you should have done it.
Also, as a pro tip, rinsing algae pads after use is a great way of controlling any pathogens that they might collect.
Washing foams in tapwater
If you’re new here, then this will be one of the most important things to take away from the magazine. Do not wash your filter foams under the tap. The foams contain bacteria, and those bacteria are helping to keep your fish alive by converting harmful wastes. Treat the foam more gently than a newborn puppy, bathe it softly in old tank water, and never, ever expose it to any kind of disinfectant.
Not cleaning pipes
Ever had that moment where you’ve cleaned your external filter, spruced up the foams, plugged it all back in and been greeted by a puff of white and brown bits blasting through your outlets? Annoying, huh?
Biofilm develops in lengths of hosing, and the on/off action during maintenance will loosen it. Clear pipes will develop algae, and trap mulm, too. Eventually these build ups can impair flow, so they need addressing.
Clean your pipes every other time you open the filter. You can buy brushes to get inside them, but I’ve always found that a purge with hot water and a funnel down the sink does the job just as well.
Using one net to catch fish
A net will cost you between £1.50 and £3. Buy two of them.
Catching fish with a single net is stressful for the aquarist and the fish. Professionals struggle, amateurs make a total ham of it. Use one net as a sheepdog to encourage the fish into the other.
Some experts claim success with different coloured nets, using a small, blue net to chase fish into a larger, green one. Others insist that fish are easiest to catch with red nets.
More importantly, get the right size. For average, 2–7.5cm/0.8–3in fish, opt for a net with a 15cm/6in width. Tiny nets are of little use for anything bigger than slow fry, while bigger nets may seem intuitively better for catching, but in practice turn out to be slow and cumbersome.
Also, if dealing with bracer bars or odd shaped tanks, bending the net can make the job considerably easier.
Buying ‘cleaner’ cats and ‘algae eaters’
Your catfish don’t clean their tanks any more than my dog hoovers my floor. Most of them have more specialist diets than the tetras and barbs swimming above them, so scraps simply will not do. Emaciated looking catfish are unlikely to be suffering internal parasites, but very likely to be undernourished. Find out what they eat, and supply it.
By the same token, don’t assume that any fish with a suckermouth is a herbivore. Many of these species, all too often euphemistically labelled as ‘algae eaters’ are devoted carnivores that prefer snail meat and other aquatic inverts, while others grow huge. Review all fish on a case by case basis, and provide the diets they need.
Medicines, tonics, salt — everything! We are a nation of overdosers when it comes to fish, without realising that too much can be more harmful than not enough.
Some tank manufacturers exacerbate the problem by stating displacement volumes instead of actual volumes. So if you buy a tank advertised as 100 l/22 gal, it may in reality hold only 85 l/19 gal of water once you’ve added the substrate and decor.
Calculate easily, and do it for yourself. Measure the length, width and water depth
in centimetres and then get a calculator. Follow the calculation below and you’ll be fine: Length (cm) multiplied by width (cm) multiplied by water depth (cm). Divide that number by 1000 and you have the volume. Multiply this number by 0.9 to deduct 10%, to account for displacement due to substrate and decor, and you have the treatment volume.
For a 120 x 45 x 45cm tank:
120 x 45 x 45 = 243,000.
243,00 divided by 1000
= 243 l.
243 l multiplied by 0.9 = 218.7 litres of water to be treated.
Assuming all tropicals should be kept at 25°C
The word ‘tropical’ has a connotation with being a very particular, set temperature.
The reality of the world is different. Some tropical fish come from high altitudes, or low ones, where the temperature can be far from 25°C/77°F. Some live in open, sun-exposed areas, while others huddle under dense, shaded canopies. Some live in deep holes in the ground, or caves.
Finding out where a fish is from and providing the right temperature is essential. Too cold and it will struggle to grow, and will have weak immunity. Too hot and it will struggle to retain weight, or may die outright.
A temperature of 25°C/77°F is a fair balance for many popular species, but even very common fish like Neon tetra like things cooler, and live shortened lives in hotter climes.
Thinking all snails are bad
The presence of millions of snails is bad, but the snails themselves are amoral, and often helpful agents, just exploiting an easy food source.
There’s a balance. Snails eat debris and detritus in a tank, along with algae and dying plants. They love it. They thrive on it.
The simple equation is the more snails you have, the more food there must be available for them. And the more food they have means that you as the owner and cleaner of the tank are doing something wrong.
Five point snail-eradication plan
1. Clean the gravel thoroughly. Remove uneaten food and mulm.
2. Go through your plants and remove any struggling leaves.
3. Review feeding levels. Are the fish leaving food uneaten?
4. Purchase a snail trap, or use a saucer with snail bait.
5. Purchase some Assassin snails to eat the stragglers.
DO NOT be tempted to:
- Add snail-eating fish like Clown loach.
- Resort to harsh snail killing liquids without addressing waste
- levels first.
- Kill snails and leave them in the tank to decompose.
Taking pity on runts
We all love to nurture the weaklings from a brood — it’s a part of our inbuilt nature as humans to take sympathy on small, struggling things. Look at why puppies and kittens are so popular.
With fish, you might be taking on an impossible task. A fish that lacks fins and cannot swim properly may have a terrible quality of life, may be pecked by tank mates, or may miss out in the competition for meals.
Or you could be inviting disease in to the home. Some deformities can be caused by viral tumours, internal parasites or bacteria. What might look like a cute one-off quirk in a store
tank could be a festering hamper of illness waiting to strike your aquarium.
The sad fact is that fish often have so many young to account for the runts, also-rans and outright failures. When you keep one of those runts alive, allow it to reproduce, and pass on the young, you’re just subjecting others to the same problem later down the line.
What to look for when buying fish:
- Well-formed body and fins. No splits or tears.
- Both eyes intact.
- Mouth opening and closing correctly, no twists in the jaw, no over- or underbite.
- Gill covers that do not leave any of the gill exposed when closed.
- Straight spines, no kinks or ‘S’ shapes.
- No lumps or bumps.
‘Growing’ plants in gravel
This is up there with buying houseplants as aquarium plants. Keep a plant badly, and it’ll die. Before it does, it’ll feed a plethora of snails and release all manner of waste into the water.
For most species, gravel is not conducive to growth. Potted plants may tolerate gravel for a while, but eventually even they will find the substrate too harsh.
If you are stuck with gravel in the tank, you can at least make ‘plant boxes’ using a margarine tub. Fill the tub partway with plant friendly substrates, place it in the tank wherever you want growth, plant greenery into it, and then hide it by covering with a thin layer of the same gravel in the rest of the tank. The plant roots will be happy, and observers will be none the wiser.
A tank in a living room can be surrounded by hazards. Minimise the risk to your fish by knowing the chemicals that can be toxic to your fish.
WORDS: NATHAN HILL
Today, somewhere in the world, someone will be looking at a tank full of dead fish and scratching their head, unable to ascertain why.
It might be something catastrophic that’s happened in the tank, a crash of the filter, or the result of a stuck, overzealous heater.
A lot of mysterious deaths are never solved, because hobbyists focus solely on what’s going on in the tank, and not what’s happening around it. The problem is, extraneous factors can be just as – if not more – deadly than anything that happens within.
If you weren’t aware of the outside influences that can cause a wipe out, then now’s the time to learn. You might be closer to devastation than you think.
Not the obvious problem that people imagine it to be, but sound can cause acute or chronic stress in fish, weakening their immune systems and leaving them wide open to infection. In extreme cases, a sudden, loud noise can be enough to shock a fish into an abrupt and immediate death.
Anything that impacts against a tank has the power to kill. Fish partially detect the world around them through their lateral line system, a sensory accessory that lets them detect the tiniest of changes in water pressure. Subjecting them to a sudden shock like a slap against the glass is the fishy equivalent of me firing a shotgun right by a person’s head. Children are among the worst culprits for tank slapping (which is why you hear so many of them being told off in aquatic stores), but pets and slamming doors can be just as bad.
The rumbling bass notes of a loud TV or stereo are enough to drive terror into most fish, so any tank situated by a speaker is prone to problems. Try to keep the home cinema and the aquarium in separate living quarters.
The air we breathe
The oxygen in your tank comes from the air around it. Subsequently anything in the air nearby can get into the water and cause problems.
Worse still, water is great at attracting airborne pollutants, and collecting and concentrating them. Your lounge might be an atmospheric soup of chemicals, and if it is, then it’s a safe bet that the levels in the water are even higher!
Some day-to-day chemicals are worse than others, and some (if you read the packaging) will even point out that they’re not safe to use in the vicinity of fish tanks. If they do, then take their advice.
Fleaspray is lethal to fish. An active ingredient — permethrin or pyrethrin — is one of the most potent fish killers you’ll find (and it’s not great for humans either). Any recently sprayed pets should be kept well away from even the rooms where fish tanks reside.
Air fresheners are all too often little bundles of death where fish are concerned. The very chemicals that bring fresh smells are frequently toxic to fish at even low doses. Spray fresheners can provide sudden acute poisoning, while slow release plug-in fresheners release chemicals that gradually accumulate. If the packaging doesn’t claim it’s safe with fish, then assume it isn’t.
Cigarette smoke is heaving with toxic nicotine, and though I’ve found nothing to verify it, I imagine that e-cigs could do the same. Some fish can be surprisingly tolerant (like goldfish) while marines are incredibly fragile. I’ve seen a whole reef tank wiped out
by a single cigar before.
Deodorants and perfumes are the reasons that many tanks in adolescents’ bedrooms can fail. Always spray them in a different room to your tank, and if perfume has been applied to wrists, then keep your hands out of the tank.
Polish is a tricky one, as nobody wants to live in a grotty room. Airborne polish is a huge issue, while impregnated on a cloth is less so. Spray the polish on to your cloth elsewhere in the house, and then use it to wipe in the tank’s vicinity, but be vigilant for signs of stress and poisoning in fish when doing so.
Paint and varnish can be as bad as each other. Don’t think for an instant that you can just cover the tank and paint around it. You’ll need to move everything out while you refresh your walls or skirting boards.
Hand soap and hand sanitising gels are great for hygiene, but it’s essential you use them after going into the tank, not before. I’ve even known aquaria wiped out by people who had been doing the dishes and still had soap residue on their skin.
If you use the same bucket to clean the car, windows, floor and aquarium, you’re asking for trouble from the cocktail of deadly chemicals clinging to the bucket’s sides — even if you rinse it out.
Insecticides may be less of an issue for fish, but outright lethal to inverts like shrimps. To leave some Eastern countries, plants need to be sprayed with chemicals that kill hitch hiking bugs and beasts. New plants that haven’t been soaked or rinsed appropriately are a common cause of shrimp deaths, making their flesh turn opaque before they die. With some insecticides, a rinse of your new plants won’t be enough, and instead they may need several days of soaking.
Fish medicine can be alarmingly toxic. Too many newcomers (and quite a few old hands) think ‘if one drop will fix the disease, two will fix it in half the time!’ Medications are designed to work at a set dose, usually just enough to be lethal to pathogens, but not quite lethal enough to harm fish. Overdoses can cause major organ damage, clubbing gills and ravaging kidneys.
Always carry out water tests away from the tank and never place the sample on top of the aquarium while you wait for the results. A spillage could prove deadly to your fish.
Salt should be handled with care. Used to excess it will accumulate in the water, and can start to dehydrate fish. It may sound odd, but it happens much more than you might think.
How to spot a case of poisoning
Symptoms can vary between fish, as well as pending which chemicals have affected them, but there are a few general things to watch out for.
Enhanced colours can often be associated with toxins in the water, as can typical stress markings such as dark bars or spots on the body.
Gasping at the surface can be from water-borne problems like ammonia, but it can easily be an introduced chemical that’s irritating the gills.
Lethargic behaviour and resting in one spot may be a natural behaviour for some fish, but when all are doing it, you’ll need to investigate.
Erratic behaviour, flicking, or trying to jump from the tank can be from a sudden change of pH, but it can also be an escape reaction from something nasty that has gotten in to the water.
How to fix it
If you don’t know the mantra already, then recite it until it’s firmly in there. “The solution to pollution is dilution!” Now say it fifty times in a row.
Water changes are essential in suspected poisoning cases. The sooner you can dilute down the offending chemical, the better. In mild cases, a course of 20% daily changes over a week will help, while outright emergencies may require 50% or more of the water in one go. There are no hard and fast rules, but remember that if you take out more then you also risk upsetting the filter.
Some media will help, especially carbon. For a quick removal of many unknowns, keep an Arcadia Polyfilter handy. They’re not cheap, and they’re quite short lived, but they can be the difference between dead fish and live ones in a crisis.
Of course, the best thing is to not poison your fish in the first place, so the moment you suspect it has occurred, you’ll want to snoop about the room and find out what’s causing the problem — then eradicate it!
The type of substrate you decide on will have big effect on how much time you’ll need to spend on its maintenance. Our guide will ensure you stay on top of what’s on the bottom.
WORDS: NATHAN HILL
A couple of weeks into owning your set-up, you’re probably looking at the bottom of your layout and thinking ‘that doesn’t look right…’
Different types of substrate need different approaches when it comes to cleaning. If you’ve gone for bleached white sand under a barrage of intense lighting, you’ll probably need to be in there, sifting away daily. If you’ve gone in for a planting substrate, you might never clean it, once.
Here’s how to deal with some of the more readily available substrates out there.
Controversial, but if you have a tank decked out with high-end, high cost planting substrates like ADA Powersand, you either know what you’re doing or you’ve made a big mistake.
Planting substrates are mainly designed to trap and slowly release nutrients to plant roots, and often come pre-loaded with food — that means ammonia. The moment you start trying to rake through them, you release those nutrients into the water column, and that in turn will lead to an outbreak of algae.
How to clean them
- Before going in the tank: Usually you don’t!
- Once in the tank: Some aquascapers suggest removing a section of the substrate every few weeks or months, and cleaning before replacing. Others don’t. My own advice is to run a gravel cleaner about an inch above the surface of any exposed parts, so that you lift any waste without disturbing the substrate itself.
- Heaving with nutrients and perfect for almost all kinds of plant growth.
- Useless for burrowing catfish or excessively dirty tanks.
- Limited choice of colours and grain size.
- Often tends to have a slightly acidic (and rarely alkaline) influence on water chemistry.
Fine natural gravel
Some modern aquarists might be a bit sniffy about this ‘outdated’ substrate, but it still has its place — by which I mean it is a total breeze to clean.
Gravels, and most famously the classic ‘Dorset pea gravel’ became a hobby staple during a time when tanks relied on undergravel filtration. Subsequently they have found themselves on the fringe of fashion, but many tank owners still persevere!
How to clean it
- Before going in the tank: Rinse thoroughly to remove any fine dust. A sieve is fastest, if you blast around 1 or 2kg at a time under a coldwater tap, shaking and swilling like chips in a fryer. Alternatively, place into a bucket and stir continuously while applying running cold water and letting the bucket overflow. Ensure the water is running off clean before draining and adding to the tank.
- Once in the tank: Use a gravel cleaner with syphon to draw water out of the tank and plunge the gravel cleaner deep into the gravel at the same time. The water will lift the gravel, swill and rinse it, then when the gravel cleaner is lifted it will drop back out. A battery or air powered vaccum will do a similar job, but less effectively. You’ll need to do this at least every two weeks, though weekly is considerably better. Monitor how dirty the gravel is each time and adjust as needed.
- The easiest gravel to clean by a mile.
- Inert in freshwater, rarely causes a slight alkaline elevation.
- Looks good in many settings.
- Hides obvious small particles of waste from view.
- Awful rooting medium for most plants.
- Can harm catfish bristles and burrowing species.
- Improper cleaning will lead to nitrate spikes and disease hotbeds.
Silver sand is the choice for numerous biotopes, as it’s similar to substrates found in lakes and rivers the world over. It can be bought in almost any aquatic store, and similar looking substitutes like playpit sand are available where it isn’t.
Despite some detractors claiming potential gut or gill problems associated with using it, it remains one of the most popular modern substrates going.
How to clean it
- Before going in the tank: Slowly, slowly is the key here. Place around 5–8cm depth in a bucket at a time, and stir continuously and vigorously while flushing with cold water. Note, this stage may take a long time, but you need to be thorough as it is hard to remove sand dust once it is in the tank. Don’t try putting it in a sieve as you’ll lose the lot!
- Once in the tank: A gravel cleaner and syphon will just lift the sand out of the tank, though you can use that to your advantage. When particularly dirty, it may pay to remove some sand with a hose this way and rinse it as though going in the tank for the first time — just be careful to limit this to 25% of the total sand, in order not to disrupt filtration. Personally, I like to gently rake my fingers through silver sand on a weekly basis, allowing any muck to lift and drop back down to the surface. Then using a syphon hose, I skim just above the surface of the sand, removing the deposits. This method will result in a fractional loss of sand, which is cheap enough to replace as needed.
- Natural looking.
- Great for catfish whiskers and fish that burrow.
- Almost always inert, doesn’t affect chemistry.
- Many plant roots love it.
- Cannot be used for deep substrates as it can turn anaerobic.
- Can look dirty very quickly.
- Can find its way into filters easily.
- Excitable fish may stir up a tank into a sandstorm.
- Strong filter flows may move it, leaving craters and sand drifts.
Love them, hate them, ignore them, but coloured gravels are often part of the appeal for a new fishkeeper. Not all coloured substrates are the same, either in size, quality or durability, so even cleaning for the first use can be a disappointment.
Before anything, get some of your proposed gravel, put it in a jug with some water, give it a couple of days and test for ammonia. Some coloured gravels are reported to leach ammonia compounds, and if they do, I’d personally bin them — or you can soak them until it goes away.
How to clean them
- Before going in the tank: Rinse gently in a colander or sieve under gently running tapwater. In many cases, some of the colour will run off, leading the aquarist to panic and stop rinsing. You need to keep going until the water runs clear, but do be gentle! The same problem will arise if placing the gravel in a bucket and stirring while gently flushing. Note that some gravels come coated in a resin that will hold in the colour, and for these you can be vigorous, though paradoxically they’ll be amongst the cleanest out of the bag.
- Once in the tank: Gravel cleaners and syphons will need to be used at least weekly to keep coloured gravel clean. The lighter the colour, the quicker algae will start to smother it, and you may find that white gravel only lasts one or two days before needing syphoning again. Be particularly careful with black gravel as it can harbour a lot of solid waste without you noticing, and may turn your tank into a ticking time-bomb of sewage.
- Pretty, if you like that sort of thing.
- Easy enough to clean once in place.
- Some fish will freak out over bright substrates.
- Some types may contain ammonia sources.
- Colours may bleach over time.
- Coarse grains will affect catfish and burrowing fish.
- Can get dirty very fast.
Coral sand has a limited use these days, being restricted to marine set-ups, and hardwater tanks (usually African). It’s actually the product of fish that eat corals, and pass the tiny coral ‘sand’ fragments out in their faeces.
Because it is riddled with calcium carbonate, it will make soft water hard, and subsequently alkaline. Never be inclined to use it in acidic tanks!
How to clean it
- Before going in the tank: Place around 5–7cm of sand in a bucket and flush with cold water while stirring vigorously. Ensure all the sand is turned over as you do this. When the water eventually runs clear, the sand is ready for use.
- Once in the tank: Use a gravel cleaner and syphon weekly or fortnightly and clean as though you would fine gravel (see previous page). In between syphoning sessions, waste from the surface can be removed with a battery powered gravel vacuum, or by wafting a fine net above it and lifting out any waste.
- Acts as a buffer in hardwater tanks.
- Fine enough for some burrowing species such as eels.
- Very attractive in the right setting.
- Intense light will cause algae growth.
- Useless in acidic and softwater tanks.
- Some grades can be very dusty initially, requiring prolonged cleaning.
- Fine particles are sometimes implicated in gill problems in some fish.
Top tips for healthier substrates
Never leave the roots of plants behind when extracting them, as they’ll decompose and churn out nitrates. Rather than pulling plants out, try digging them out.
When cleaning substrates before adding them to your tank, use cold water instead of hot. Some substrates can give the illusion of cloudy run-off water when hot water is used, when in reality they are clean. Microbubbles may be a culprit here
Use nets to remove uneaten food and debris rather than letting it settle on the base.
For marine tanks, lay your sand out thinly on a tray and run over it with a powerful magnet before use. It’s rare, but occasional metal fragments in substrates are not unknown.
The joy of snails! While poorly managed snail populations can become epidemics, having a few Malaysian trumpet snails among the substrate can help turn it over and prevent stagnant patches.
Older aquariums can have issues of their own, leading to dead fish and terrible water. The tragedy is that it’s so simple to avoid this kind of problem, says Nathan Hill.
If you’ve kept fish for anything more than a couple of days, then you’ll be either directly or indirectly intimate with the problem of new tank syndrome, often abbreviated to NTS.
I won’t dwell. We should all know the basics of new tank syndrome, though discussion about the exact mechanisms is heated. Fish make waste, the filter struggles to cope with that waste, and contingency plans need to be in place. You might prefer ex-situ tank maturation or in-situ. These are arguments for another time.
Unfortunately for many fish, too many aquarists assume that new tank syndrome is the only water worry they’ll ever face. They imagine that this initial establishment period is the only time they’ll struggle with instability.
Because of this, they may be caught out by an equally dangerous, yet easily avoidable problem later down the line: old tank syndrome, or OTS.
In old tank syndrome, the definition of 'old' is open to some discussion. Tanks that have been running successfully for months or years may slowly turn bad, or they might suddenly crash altogether, with multiple casualties and a befuddled owner.
The problem all too frequently lingers unseen, and then manifests itself in a way that leads to conflict between fishkeeper and retailer.
Imagine the scene, if you will. A fishkeeper has a tank that they’ve kept successfully for two years. In that time, some fish have grown, while others — conceivably through old age — have died. The plants are large, maybe a little leggy, but still alive, and overall there is no reason to suspect any underlying malaise.
This fishkeeper opts to buy some more fish from a local store, deciding to pick up some delicate tetra types, given how 'mature' their tank is. A day or two after adding the fish, problems are noted. They look bedraggled, and show the first signs of whitespot. Not long after, the tank is knee deep in a full scale Ichthyopthirius pandemic, with old and new fish dying everywhere.
The immediate impression of the fishkeeper is that they have been sold diseased fish, and so they return to the store to confront the retailer and demand replacements — only to discover that every one of the original tetras still in store is the absolute picture of health.
As is their right, the retailer requests a sample of the fishkeeper’s aquarium water before a resolution can be made, and that sample, when it arrives, turns out to be diabolical beyond compare. So bad, in fact, that even without the new fish, the tank would have been weeks away from a wipeout anyway.
And that is how most people meet old tank syndrome.
More to water than filters
If I was going for an easy sale in a store, and I had to describe a filter’s function as simply as possible, then I might be inclined to say that 'it takes all the toxic waste and makes it safe for the fish to live with'. I suspect that for a lot of casual fishkeepers, that’s the impression they have in mind. Fish make waste, filter resolves waste, problem solved.
If only it was that that simple.
Filters only convert waste, and certainly not into something safe. Ammonia from fish is converted through nitrite and into nitrate. That much we all know, right? Water chemistry 101 right here.
Nitrate isn’t exactly a 'nice' chemical to have around. In humans, it’s implicated as a carcinogenic, while the lethal levels for different fish are slowly being understood.
As long as the filter is working, and as long as the fish are producing waste, then there will be nitrate produced.
It would be wrong to say that some fish develop a tolerance for nitrate, because that implies that they can be unharmed by it. Rather, I consider long-term nitrate exposure in fish as analogous to alcoholism in humans. It slowly affects organs, reduces lifespans, and plays havoc with immune systems. To be in optimal health, they need to live lives devoid of it. Like drink in humans, a little bit of it might not be a major problem. A lot of it is.
The problem is that aside some slight loss of condition, maybe dull colours or lethargic behaviour, there’s little to see that suggests a fish is suffering in high nitrate levels.
Even worse, if a fish is then taken from water where there is very little nitrate (such as in the case of my hypothetical retailer earlier) and suddenly exposed to high nitrate, then it is likely to shock it. To stay with the drinking analogy, someone unhealthy but used to drinking heavily would cope better with a ten pint boozing session than a person in perfect health who has been a lifelong teetotaller. Think Rab C. Nesbitt versus a nun. It’s a crude way to explain it, but that’s pretty much what happens.
There’s also phosphate to consider. Phosphate is introduced courtesy of the foods we offer our fish. It is not metabolised to any degree, and ends up excreted as waste.
Phosphate has questionable health impacts on fish, and is much better understood to inhibit invertebrates. Marine keepers in particular struggle to control it. As phosphate builds, the most obvious symptom is increased algae growth. In waterways, excess phosphate leads to eutrophication (it is the prime cause of eutrophication), which turns rivers and lakes bright green with algae, stripping the water of oxygen and killing the inhabitants. Such pandemics are not well known in aquaria, though that’s not to say they never happen.
Again, all of this is very easy to avoid.
The acid effect
The worst culprits for OTS are tanks that become victims of their own success.
An underlying problem involves the hardness — the mineral content — of the water. Carbonates play a vital role in buffering aquarium pH, as well as providing a source of carbon for some plants and bacteria: specifically those bacteria helping to convert fish waste.
When carbonates become depleted, two problems follow. Firstly, the osmoregulation of many fish (the way in which they regulate their minerals in the body) is compromised, sometimes to lethal extents. Secondly, without the buffering effect of minerals to keep it in place, pH in the tank can drop or swing wildly, leading to acute acidosis. Either of these can kill a fish outright, and both will cause acute and chronic stress.
Bacterial action inside the filter further alters pH. Biological bacteria, as they work, produce quantities of hydrogen ions. In water, these take the form of hydronium, and the amount of hydronium relative to the amount of hydroxide dictates how acidic the tank is. The more hydronium, the lower the pH, and with a busy filter churning the stuff out, pH levels can soon plummet. Combine that with the simultaneous removal of buffering carbonates as already mentioned, and you have a pH disaster in the waiting.
To make things even worse, if the pH does drop too far then it will stop the filter from working properly. In acidic conditions, the bacteria that convert ammonia struggle to function, and below 6.0pH they might stop working altogether.
Prevention trumps cure
Every parameter mentioned here can be tested, inexpensively and easily. Liquid kits, dip strips, monitoring devices — there is no excuse. Folks who say they can visually assess their tanks are deluding themselves, at the peril of their fish. You cannot ‘see’ the nitrate content of a tank any more than I can 'see' the alcohol content of a glass of gin.
Over the years, there has been something of a misunderstanding. Many aquarists are only keen to test — or in some cases have their retailer test for them — while they are cycling the filter at the start of the tank’s life, and wrongly assume that once that’s out of the way it’s plain sailing.
Testing for the chemicals associated with old tanks needs to be performed weekly, or fortnightly at least. Nitrate, GH, KH, phosphate and pH are all reliable indicators for the health of your tank. At an absolute minimum, nitrate and pH need to be closely watched.
Start by testing your water supply, whether you use tapwater or RO mixes purchased from a store. Unless you are deliberately altering the water in the tank with acidic products like Catappa leaves, then a difference of 0.5pH between the aquarium and the water source is a huge cause for concern. Nitrate levels always need to be low, but if the tank water tests at 40ppm greater than the water source, alarm bells should be ringing.
If you test for phosphate, then levels in the tank should be no higher than 0.5ppm greater than those in the water source. At 5ppm or more, action is essential.
GH and KH levels in the tank should be no more than a couple of degrees lower than source, though it’s likely that KH will deplete faster out of the two. Unless you’re keeping incredibly softwater fish, a tank reading below 5°KH is a warning that cannot be ignored.
Testing is one thing, but the actual process of prevention counts for even more.
The way these issues are avoided is simple: water changes, gravel cleaning and maintenance. There’s no short cut here, and no way to avoid the inevitable. Old tank syndrome is caused by a lack of tank care, plain and simple.
Water changes will fix most things. Taking old water out and replacing it with fresh will dilute down the levels of nitrates and phosphates. Because the newer water will be richer in minerals, it will also help to boost hardness, increasing the GH and KH, and stabilising pH.
If the tank is in a bad way, then opt for a course of small changes — one won’t be enough. Changing 25% daily or every other day will slowly bring things back to where they need to be.
If things really are extreme, to the point of a tank crash, you may want to perform a larger change of 50–75%, though this is a drastic measure. Adding a mineral product such Tropic Marin Remineral Tropic will help instantly boost the GH and KH. An excess of ammonia in the water may be treated with the likes of API Ammo Lock. Nitrates and phosphates can be reduced by using dedicated resin media placed into the filter.
Essentially, all of these points need to be tackled at once. Addressing nitrate levels while the pH plummets is like washing a car while the engine is on fire.
Cleaning gravel is paramount to avoiding OTS. All of the 'hidden' waste down amongst the substrate will gobble up carbonates, and churn out more nitrates than a rotting tree. Left too long, aquarists can even face the rare but lethal hazard of hydrogen sulphide production, where oxygen levels in the gravel drop so low that the 'wrong' kinds of bacteria can proliferate.
A simple gravel syphon will keep on top of this collected slurry. Using a cleaner like the Fluval AquaVac+ will pull up much of it, though it’s just as easy to combine gravel cleaning with a water change and kill two birds with the same stone.
Maintenance is essential, especially for the filter and any plants. Filters accumulate waste much like the gravel does, while some media which removes the likes of nitrates can become exhausted and release much of what it has trapped back into the tank. Frequent changing of resin media, and regular cleaning of sponges is vital.
Plants can also contribute to OTS if kept poorly. Old leaves may drop or degrade, and then they’ll start to rot — meaning more carbonate depletion and more nitrates!
By combining regular water testing with regular water changes and maintenance, there’s no reason for anyone to suffer from old tank syndrome.
You never know, those basic chores might even save you from having an embarrassing fracas with your retailer one day over dead fish..
Potential causes of OTS
- Inadequate water changes.
- Overstocked fish levels.
- Dirty gravel.
- Uneaten food.
- Unwashed filters.
- Dead fish/shrimps/snails.
- Decaying plant matter.
- Low GH or KH water supply.
- High nitrate water supply.
Unsightly and agonising, gas bubbles in fish are a horrific infliction - and usually man made! We explain more.
The symptoms of gas bubble disease are obvious. They are small or large pockets of shiny, silvery gas trapped beneath the flesh in some grotesque, glistening lump.
These may be unsightly and look painful, or have more serious health implications. If bubbles start to form inside around the vital organs, such as the brain, liver or heart, then death can be rapid and without warning.
Even outside the fish they can be major health problems. Bubbles around the mouth will hinder feeding, those behind the eye affect vision and bubbles on the body make swimming difficult or painful.
The name 'disease' gives a false connotation that this is in some way a pathogenic condition, but it’s rarely the case. Sometimes, although incredibly unlikely, bacteria may get behind an eye and produce gases as a result of their growth.
Usually the condition is brought about by problems in filtration and circulation. This is more apparent in marine tanks where the density of the water allows for the formation of smaller bubbles than in freshwater — although both types of fish can become sick because of gas embolisms.
Most often, the culprit is an ill-fitting pipe. As water travels through filters, even the tiniest gap or lesion in the hosing can draw in a tiny Venturi of air. This suction of tiny strings of bubbles can start to accumulate in the water until a level of saturation is reached.
These micro-bubbles then enter the fish via the gill, where they start to accumulate in the blood, sticking to each other and forming ever larger bubbles. The process soon accelerates, to devastating effect.
Another, lesser known way for these bubbles to enter fish is through sudden additions of cold water to the tank.
Colder water holds more dissolved gases than tropical water, and, as it warms, these gases will precipitate into tiny bubbles. Just take a cold glass of water to bed one night and look at the formed bubbles in the morning. You’ll see how much there is.
If cold water is added and fish breathe it, the same process will happen inside them. As the fluid warms it releases gas that then forms tiny bubbles inside. The bubbles accumulate and once again we have a problem.
Over time gas bubble disease will cure itself, assuming that the cause of the bubbles is addressed. At the first sign of this problem, check all piping thoroughly and find where the air’s getting in.
Never consider bursting the bubbles. This will harm the affected fish, leave it open to infection, and the stress will often lead to secondary infections. Rectify the cause and leave the fish alone — every time.
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No aquarist wants to see hole in the head (HITH), or head and lateral line erosion (HLLE) in his or her fish. We investigate the orgins of this difficult to treat ailment.
HITH and HLLE are basically the same thing; the first confined to the head region and more prevalent on freshwater fishes, the other starting at the head and moving down the sensory canals that run the flanks of marine fishes’ bodies.
As aquarium diseases go, it’s quite an enigma. We can recognise the symptoms, albeit in the latter stages of an outbreak, but defining the cause is much more of a challenge. Treatment is more difficult again.
There are pathogens associated with the condition, diplomonad species of Hexamita, Spironucleus and Octomitus, but whether these are causes or opportunists making the most out of a bad situation is unclear.
In post-mortem examinations, both have at some point been implicated as connected, but to simply blame the pathogen is to miss out a big part of the story.
An infected fish usually develops pale, eroding holes over the head which can then proceed to move either side of the body. These patches of degradation enlarge, making the fish look as if it is being eaten alive by some unseen bug.
At this stage the fish is in real trouble. Not only is its immune system being heavily taxed, but the open lesions provide an entry point for other pathogens that can cause systemic illnesses — much like the bacteria that can enter a human body through a decayed tooth and lead to heart issues.
Causes of HLLE have been long debated, although nobody can say with certainty what is the main trigger. Activated carbon, specifically the dust it produces, has been linked with outbreaks in marine fish such as tangs.
Fish seem to improve when taken from tanks with activated carbon and those unexposed to it have a lower likelihood of infection.
Other factors discussed include nutritional deficiencies, especially key vitamins and dietary iodine. Improvements in nutrition have been shown to benefit affected fish.
It seems water quality can equally play a role. Fish kept in aquariums with high nitrate (NO3) levels succumb to the illness more readily than those that don’t.
Even stray voltage has been accused of bringing about the disease, with tanks that carry electrical currents supposedly enhancing susceptibility.
Role of stress
We can say with some clarity that stress plays a significant role and at the first instance of the illness any adverse conditions must be rectified immediately.
Treatment is reported to be effective in some cases, but not in others. A range of anti-pathogenic medicines is available, although many aquarists will lean towards those that contain the active ingredient metronidazole.
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Jeremy Gay shows how you can easily create your own quarantine tank on a budget.
A quarantine tank will save lives. Fish can be slowly acclimatised and screened for infectious diseases, sick ones can be medicated and you can even breed in one!
The components for one of these are the most important purchases you’ll ever make — and this complete example would set you back just over £62.
The legendary Clearseal 46 x 25 x 25cm/18 x 10 x 10” aquarium has been used in the set-up shown above, complete with plastic hood and polystyrene tile cushioning underneath. It’s large enough to quarantine fish up to about 10cm/4” in length and small enough to be portable.
You don’t want a light in the hood as bright light will stress sick fish and break down medication. The lid also prevents irritated fish from jumping out.
Air-powered sponge filter
This provides gentle mechanical and biological filtration, along with extra aeration at the same time. Sick fish can’t swim against strong currents and will tire quickly. No provision for chemical media means that you won’t accidentally remove a medication with carbon either.
Essential for tropical fish, place a combined heater/thermostat diagonally across the rear tank glass to spread heat evenly.
Choose a model that’s easy for you to adjust and that can heat up to more than 30°C/86°F — a key factor in fighting parasites like whitespot.
Don’t underestimate the usefulness of this piece of earthenware. Cave spawners will breed on it and shy fish will hide in it. It’s also useful for sick fish, as they can back up into it and feel more secure.
It won’t affect water quality or medications either.
This is essential for at-a-glance temperature monitoring. Heat can be an effective weapon in fighting parasites, so this way you can ensure that everything in the tank is as it should be.
These give cover to nervous fish. The designs here are pre-weighted by a resin base. They are fine with medications and won’t affect water quality by dying off and polluting the aquarium.
Quarantine tanks are left bare for a reason. Part of the life cycle of some parasites involves a stage that lives in the substrate — so by having bare glass it will interrupt reproduction and, in the case of large parasites or worms, will help you spot them on the tank base.
Get a test kit
Fish won’t get better in poor water so it must be monitored at all times. Run your quarantine water as you would in your main tank, making sure that the water conditions are ideal for the species housed. Optimum water quality will aid recovery.
How can I avoid new tank syndrome?
This question often arises when quarantine tanks are discussed. If you maintain one with no fish the bacteria will die off through lack of food — causing you problems when you do eventually add fish.
Prevent this by placing the sponge of the filter inside a filter in your main tank. Then, if you need the quarantine tank for new fish, sick fish or breeding, move the mature sponge over to instantly provide filtration.
If the fish is sick, when you have finished treating, either sterilise or replace the old sponge with new and place back inside the main tank’s filter for re-maturing.
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Suddenly discovered a tragedy in your aquarium and not sure how to handle the situation? Here are five tips to help spot any problem and hopefully prevent more casualties.
Check your fish every day when feeding them and do a quick head count and health check. Are they all there? Six Neons, three Corydoras? Are they all doing what they should be?
If a fish is missing check the corners of the tank and open the hood to find out where it is, as any hanging around by the filter instead of with friends is a bad sign.
You may not be able to see the missing fish at all. If so, step up your search and assume it is dead. Depending on species and length of decomposition, the corpse could be stuck to filter inlets, floating at the surface, lying on the bottom, under décor like rocks or wood or caught in plants.
Check all areas until the fish is found. If it’s dead, move to step two.
Any dead fish should be removed, as its body will quickly rot in the warm, bacteria-laden water. A corpse will pollute water, risking the health of other fish in the tank.
If it died from disease the last thing you want is other fish consuming its body parts, so remove immediately.
If you have found the corpse quickly enough you may be able to give it a quick once-over diagnostic check.
Are the fins intact? Ragged or split fins and scuffed skin may mean the fish was bullied or beaten to death, as is often the case with Malawi cichlids.
Is the body bloated as in the picture of the goldfish above? This could indicate an internal infection.
4. Test water
Every time you find a dead fish you must test the water to check everything is OK, as water quality, or failure of it, is the biggest cause of fish deaths. Test water straight away and be prepared to remedy it if anything rears its ugly head, like ammonia.
For an emergency water change, arm yourself with a syphon and bucket, dechlorinator, thermometer, filter bacteria booster and, of course, a test kit that tests for ammonia, nitrite, nitrate and pH.
5. Seek advice
Water test results will go one of two ways. They will either indicate fine, in which case you must look at other causes, or they will alert you to a water quality issue that in itself will need addressing.
If the water is fine you need to look at other factors like disease, starvation, long-term stress through inappropriate conditions, like softwater fish in hard water, or the least likely, but still possible, old age.
If it was part of a species group in your aquarium what are the other fish looking like? If they are OK this is a good sign. If they are all acting differently or looking decidedly ropey they might soon be dead too.
Write down the results of your water test, along with all the other details of your tank, like tank size, filter model, time set up and food, and consult an expert.
Is it playing possum?
Be wary that some catfish like to wedge themselves into tight spaces, making it look like they’ve become trapped and have died.
Humbug catfish in particular do this, and many have met their fate by being removed along with their wooden home.
What’s the best way to get rid of the fish corpse?
Flushing is tempting and quite hygienic, though we doubt your local water board will appreciate various exotic fish species potentially blocking their soil pipe network.
There may also be a disease risk to native species via the waterway too, so don’t do it.
Binning is an option, though hot days will mean an awful smell, flies and maggots. Seal the corpse in a polythene bag to avoid this — though the smell will still escape!
Burial is safe and may be a good option for larger fish to avoid rotting corpses in bins. Incineration via bonfire is also possible, though you will then be left with debris.
How many deaths are deemed acceptable in a community tank?
It depends on how many fish you have and what they are.
Generally, small fish like Neon tetras and smaller are quite short lived, whereas large catfish and cichlids are long lived.
So if you have say 50 assorted small fish, all added at different times, you may lose a dozen a year for various reasons.
It’s when you lose several of them at once, or different species at once, that the alarm bells should start ringing loudly.
When can I restock with fish after any deaths?
It depends on what the cause of death was. If the water quality was perfect and all other fish, including members of its own species, appear OK and look free of disease you could restock within a week.
Leaving it for a full seven days is best, as if others die within that time you’ll know there’s an underlying problem.
Don’t be tempted to restock and add lots of others, as this in itself can cause a water quality issue. Add a few fish each week and observe behaviour.
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Think you know all about salt? Nathan Hill looks at startling new research that may change your mind.
Salt may not be the cure-all for certain illnesses. After decades touted as the comprehensive remedy, new findings suggests that in some cases sodium chloride (NaCl) actually helps particular parasites.
Researchers, writing in the journal Aquaculture, have tested this treatment not on species unfamiliar to the trade, such as trout, but focussing closer to home on the guppy (Poecilia reticulata) and two known species of Gyrodactylus fluke (G. bullatarudis and G. turnbulli).
This host and parasite combination can be a nuisance. Guppies are natural hosts for both species and in the crowded, stressful conditions in which they are transported and kept the parasite often overcomes the fish’s weakened immune system.
To replicate real life conditions, the researchers selected a variety of known used dosage rates — from long-term low level baths within the regions of 1-7grams per litre to shorter-term dips of higher concentrations as far as 33g/l. They used a range of online forums to determine ‘folk dosage’ of salt, basing studies against actual parameters used by aquarists.
It should come as no surprise to find a direct link between higher dose rates and increased mortality of the parasites, but one result is certain to ruffle feathers. This is the discovery that at a long-term bath at the lower dose rate of 3g/l – a level often touted as good for fluke control – the Gyrodactylus grew faster than on those control fish simply in dechlorinated water. The salt actually helped the parasites establish themselves!
At a higher concentration of 7g/l, a positive effect was seen with both species of fluke hindered. These levels are acceptable to guppies with their higher tolerance of salt, but would be difficult to apply to more sensitive species.
Best results were attained against both species of fluke from a short- term dip. Subjected to a 25g/l bath for 15 minutes (adults) and five minutes (juveniles), all G. turnbulli were eradicated, with 73% of G. bullatarudis going the same way.
Evidently, dipping is more effective in controlling these flukes, although it was noted that, post-treatment, elevated levels of mortality were observed in the juvenile fish.
Speculation regarding why the long-term dose rate increased parasite growth involves the nature of the pathogen itself. The fact that it inhabits the mucous layer of the fish could be to its advantage.
Gyrodactylus flukes feed on mucous, but this layer also protects them from factors in the external environment. Initially, on adding salt to water, fish will increase their mucous production, providing both cover and nutrition to the very pathogen we are trying to control.
Eventually, as mucous cells are depleted, this would both starve and expose the parasites. However, if we need to expose fish to medications that cause them to annihilate their own immune responses, then something has gone very wrong.
This is not to debunk salt as a medication, but it indicates that between pathogens there are marked differences in using salt as a disease control. For example, salt is more effective at lower, ongoing doses in controlling whitespot when the problem is not confined to parasites hiding within the mucous of the fish, but rather free swimming as theronts searching for a host.
When whitespot infection is both below the mucous and embedded in the skin, it’s unlikely that short-term baths will have any effect against this kind of pathogenic behaviour.
Prevention is always preferable in trying to cure established illness and medicines should be used only to treat specific pathogens.
However, guppy keepers should think twice before dosing their aquarium at 3g/l of salt, ‘just in case’ they get Gyrodactylus. In trying to do the right thing they may be promoting the very disease they want to control.
Nathan Hill answers your most frequent questions about one of the most lethal killers of aquarium fish.
What actually is NTS?
New tanks ruin many a hobbyist’s first excursion into fishkeeping. All aquaria require a period of running in, or establishing before holding their first full compliment of fish. New tank syndrome (NTS) is caused when this introductory phase is imbalanced by adding too many fish at once
The problem begins to manifest itself as fish produce wastes that build up in the aquaria. Bacteria will then culture inside the filter and consume this harmful waste. However, these require many weeks of growth before they can cope with the amount produced.
Adding too many fish at one time will produce fish waste quicker than the bacteria can reproduce to consume it. Once waste production exceeds bacterial growth, fish will be subject to poisonous levels of their own pollution, causing illness.
How does it kill the fish?
The toxins fish produce are highly poisonous. In the initial stage of new tank syndrome there’s a build-up of caustic ammonia, although the amount that will actually harm fish depends heavily on other factors, such as pH and temperature. A hot, alkaline tank is much more dangerous than a cooler, acidic one.
Ammonia burns the fish and the symptoms are obvious. The fish gasps at the surface, its delicate gill membranes having been damaged — or it just tries to escape the hell of the aquarium’s conditions.
Nitrite is another nasty produced in this initial phase. It kills by altering the blood of the fish, saturating it with something called methemoglobin which then competes with hemoglobin for the uptake of oxygen.
Methemoglobin adheres to oxygen but does not release it, causing the iron in the blood to rust and become useless. In this way the fish will actually suffocate from within.
Both chemicals, when present in the water, will eliminate the immune system of the fish and leave them susceptible to further diseases and infections.
Why does it last so long?
The bacteria required to convert these chemicals take a long time to find their correct home in the filter, as well as paradoxically being inhibited by the high levels of the very waste that they’re supposed to be consuming.
Other factors inhibit their growth, such as oxygen level which needs to be very high.
However, the biggest hindrance to the growth of bacteria is usually down to any incorrect cleaning of the filter medium on which they are growing.
What do the bacteria need to grow?
Food is important, in the form of fish waste. They also need somewhere to live and often a filter will have a dedicated home in the form of filter media with a high surface area. All the better to house more bacteria (pictured above).
Possibly the most pressing requirement is oxygen. They require so much of the stuff to function and the moment levels start to drop then water quality will rapidly follow suit.
Why has it affected me?
You’re not alone if you suffer. Everyone who sets up a new aquarium, from absolute beginners, through breeders, to hi-tech public aquaria, will be subject to new tank syndrome of one severity or another. It’s perfectly normal and sadly an unavoidable part of the fishkeeping process.
How do I address the problem?
There’s no easy fix. Many people have tried to find one and although we seem to have some short cuts, there’s no real way to avoid it.
What do I need to see me through?
The most important things you’ll need are a length of syphon hose, good supply of dechlorinator, reliable test kits and a reserved approach to feeding fish.
Monitor water quality frequently over the initial period of establishing the tank — and that’s going to last a good six to 12 weeks. Test kits for ammonia and nitrite are crucial and if you can afford no others ensure you have at least these two. They’re not perfect, but will help.
Be in control of feeding for the first few weeks and remember that underfeeding is preferable to overfeeding. Excess food produces higher levels of waste, making more work for you and unsuitable conditions for the fish. You can fatten the fish back up once this dangerous first stage is passed.
If the ammonia starts to get anywhere around 1ppm then change some water. Likewise, aim to keep the nitrite level low, under 1.5ppm if you can. These levels will eventually go altogether once the bacteria start to do their thing, but they’ll need to be diluted down with water changes if they start to creep up.
There’s no need to be too drastic and smaller, more frequent changes are preferable to large intermittent ones — if for the sake of the bacteria alone.
When you perform a water change or clean the filter don’t use any water containing chlorine. This is put into tapwater to kill off bacteria and is very efficient is doing so.
However, it will wreak havoc on the bacteria you are trying to culture in your filter and remember that without the bacteria there’s nothing happening to control all that fish waste. In effect, the bacteria are the filter.
What about filter starts? Don’t they help?
Some definitely seem to work and research backs them up. Others seem to work on paper, but do nothing in the aquarium. At the very least, these filter starts don’t make things any worse and are certainly worth investigating, especially if you are having problems with lingering pollution levels.
Your local retailer should give you an honest opinion about which do and don’t have an effect.
So do I put fish in to start with or not?
Practical Fishkeeping says no. In an ideal world, with ammonia alternatives readily available and the whole process reduced to a few easy stages, leave the fish out. However, some may argue, in adding a few pollution-tolerant fish to the aquarium and slowly building up the stocks you know exactly where you stand.
If you're going to start the process with live fish be aware that you are about to stick them into imperfect conditions and you are directly responsible for their well-being.
If starting with live fish you must also start with test kits, otherwise you’re just guessing at what’s going on and that’s not fair on the living organisms which stand to lose everything if it all goes wrong.
How long can I leave it before adding any more?
This varies from tank to tank, but you won’t be able to add more until the ammonia and nitrite have dropped back down to zero. Even at that point you’re not completely out of the woods!
How long until the tank is fully mature?
Technically it never is! The tank will only ever develop enough bacteria to cope with the waste of the fish in it. If you have ten fish then you have a corresponding ten fishes’ worth of bacteria. Add another ten and suddenly the tank needs more maturing time to cope with the extra levels of waste.
This way, the bacteria can be seen to be fluid in their population, not static. Sudden overfeeds that cause a spike in pollution can affect their numbers and, in extreme cases, they just can’t cope with sudden onslaughts of waste.
Check out our other feature in this series:
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Whitespot is a potentially lethal disease. Hereâ€™s how to understand and treat it.
What is it?
Whitespot is a protozoan fish parasite. Its scientific name is Ichthyophthirius multifilis and in the US this is frequently abbreviated to its other common name of Ich.
What causes it?
It’s said that all fish carry the whitespot parasite and that when fish are stressed, their immune systems are affected and, like us, are much more vulnerable.
A major cause, especially in the winter months, is sudden temperature drop brought on by changes with water becoming much cooler than that in the existing aquarium.
How do I diagnose it?
Whitespot is one of the easiest diseases to diagnose, even by novices, as the fish become covered in tiny white spots. The fins are usually worst affected. The spots are actually cysts formed over the parasite itself, which isn’t visible to the naked eye.
A severely affected fish will be visibly lethargic, flicking or clamping its fins, and basically much less active. If left untreated, whitespot can quickly kill a fish and spread to others in the tank.
It will always be more visible on fish with solid, dark colours like Black moors or Black mollies, and much less visible on patterned or white fish, so always inspect all your livestock carefully. If one fish has whitespot, assume all your fish have it and treat the entire tank.
How should I treat it?
Whitespot is one of the most common aquarium fish diseases, and several manufacturers produce a liquid whitespot remedy available via your aquatic shop or website.
You calculate the volume of your tank and treat accordingly, with many instructions advising dosing over a seven-day period to kill off the parasite at different stages of its short life cycle.
Remove carbon from the filter when medicating.
Other treatments should really be used alongside a whitespot medication, like turning up the water temperature to as high as 30°C/86°F if your fish will tolerate it, as this speeds up the life cycle of the parasite. Also add salt — which nine out of ten parasitic diseases don’t like.
If you see any small white spots looking like grains of salt stuck to the fish act fast, as if whitespot gets inside the fish’s gills it will be in real trouble.
A long-term prevention measure includes running a bare-bottomed tank (as the parasite has a substrate dwelling stage) and fitting a UV steriliser to your external filter.
Check out our other feature in this series:
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One of the most visible goldfish health problems has a very common cause. Take our advice to find out what to do if your goldfish starts to turn upside down.
What is this problem and how can I identify it?
It’s easy to spot. A goldfish suffering from a swimbladder disorder will be floating at the surface and not able to dive. It will be swimming on its side or often upside down at the surface, but, apart from that, appear healthy.
What causes it?
Although frequently referred to as swimbladder disease, few if any floaty goldfish have anything terminal. Instead, it’s caused by one thing — food.
Fancy goldfish aren’t great swimmers, due to their double tail fins and short, fat bodies. Within their bodies the swimbladder, which controls buoyancy, is bent, so doesn’t work as well as it should.
Feed them foods that contain air, like flake, floating sticks or floating pellets, and the fish take in air as well as food. The result is a fish looking as if it has a giant air bubble as it floats to the surface and then can’t right itself.
How can I fix it?
The natural reaction of the goldfish keeper is panic. In the fish world upside down often means dead, so naturally it’s assumed that even though it is still breathing it is close to death. Far from it.
Next step is to seek a remedy and these are often available as a treatment for swimbladder disease, and the advice given is to add some salt. Both are administered, yet weeks later the problem persists. As mentioned it’s not a treatable disease, merely a result of short-bodied fish with bent swimbladders accumulating air.
The real remedy is not to feed for 24 hours. As a result of the many times we’ve experienced this you’ll find that when it isn’t fed, the fish doesn’t float. After that only offer sinking foods like Tetra Gold Japan, Hikari Lionhead and Saki Hikari, and lots of frozen foods like bloodworm, Daphnia and brineshrimp. Problem solved!
What long-term precautions can I take?
It seems that only the fat-bodied, fancy goldfish varieties experience this inconvenience, while the more slender, single-tailed Common goldfish, Comets, and Shubunkins don’t suffer.
So you could just avoid fancy goldfish altogether and instead keep hardier, more natural goldfish!
However, if fancies are your thing, be aware that generally the shorter the body the more compressed the swimbladder — so avoid the extremely fat varieties like Pearlscales and short-tail Ryukin and instead, go for the longer-bodied fish.
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Dr Peter Burgess, Senior Consultant of the Aquarian Advisory Service, takes us through the alphabet, looking at the common â€“ and not-so-common â€“ health matters that can affect our fish.
Genus of aquatic water moulds (aquatic fungi). This is a common cause of fungus infections of freshwater fish and fish eggs. Manifests as one or more white-grey cotton wool-like growths that project from the body surface, such as skin, fins, eyes or gills. Typically, only a single fish is affected.
Treat with a proprietary fungus remedy and some products contain malachite green and formalin as active ingredients. Salt-tolerant fish can be treated with aquarium salt (1-3 grams per litre). Novel fungus remedies include bronopol, marketed as Pyceze, and Pimenta-extracts (for example. Pimafix).
Saprolegnia rarely attacks healthy, unstressed fish, so investigate why fungus initially took hold. Possibilities include unhygienic water conditions, overcrowding, skin injuries or infections, poor diet or exposure to water temperatures below fish’s tolerance range.
An infectious organism having invaded tissues or organs already damaged by another (primary) infection. For example, a whitespot parasite infection will damage and breach the fish’s skin, making the skin vulnerable to secondary bacterial infections. In many cases, these secondary infections ‘finish off’ the fish if not treated in time.
As fish age they begin to lose condition and may develop organ malfunctions and skeletal problems such as curvature of the spine.
Their immune system becomes less efficient, making them prone to infections such as finrot and tumours. The ageing fish may become thin and its colours fade.
Ensure that senile individuals are still able to compete for food and are not the victim of attack by tank mates and, if necessary, remove frail specimens to a peaceful ‘retirement’ aquarium.
Blood poisoning caused by the presence of toxin(s) in the blood. Most cases involve toxins produced by pathogenic bacteria (such as various species and strains of Aeromonas, Pseudomonas and Vibrio) that have entered the fish’s bloodstream. Septicaemia can manifest as widespread reddening of the fish’s skin and sometimes enlargement of the blood vessels (hyperaemia) that run through the fins. In some cases it shows up as brown blotches on the skin (as sometimes observed in affected goldfish).
Septicaemic fish may appear ill, lethargic and are likely to die unless promptly treated with antibiotics from the vet. Over-the-counter bacteria remedies are less effective. Good aquarium hygiene will reduce risks of bacterial infections that can lead to septicaemia.
Important skin parasites of fish belong to four groups:
- Protozoa (such as Ichthyophthirius – whitespot; Piscinoodinium – velvet; Trichodina)
- Flukes (notably Gyrodactylus species)
- Crustaceans (Lernaea – anchor worm; Argulus – fish louse)
- Leeches (Hemiclepsis and Piscicola) generally only a problem in ponds).
Most skin parasites attach to fish to feed on mucus or skin cells. A few, such as the fish leech and fish louse, use piercing mouthparts to puncture a skin capillary for a blood meal.
Harm caused by skin parasites
Individually, most skin parasites are too small to cause significant harm. But in large numbers their collective damage can become life threatening. Some irritate or physically damage the fish’s skin. The tiny Trichodina has a circular array of sharp ‘denticles’ that abrade the skin surface as it moves over the fish. Equally menacing are the curved hooks that skin flukes use to attach to their host.
The whitespot parasite employs tissue-digesting enzymes and physical force to reach its site within the skin. The blood-sucking fish louse causes deep feeding wounds as well as abrasions with its spiny leg-like appendages.
These forms of parasite damage cause breaches to the skin’s protective barrier, rendering it highly vulnerable to infection by bacteria, fungi, and other pathogens. It is often these ‘secondary’ infections that eventually kill the fish.
Physical damage and tissue-digesting enzymes irritate the fish’ skin which may react by secreting copious mucus, causing the affected areas to take on a greyish or milky appearance (‘slimy skin disease’).
Affected fish may exhibit signs of irritation, such as repeated body rubbing, jumping, darting, or actually leaping from the water. Any outward symptoms, such as white spots, may help to identify any skin parasite involved.
Treating skin parasite problems
Fortunately, numerous over-the-counter remedies are available. Most types of skin parasite have life cycles that include free-living stages in the water or substrate — so as a general rule medicate the whole aquarium or pond in order to completely eradicate them.
Scale erection (raised scales)
In this abnormal condition some or all of the fish’s scales project outwards, giving a serrated or 'pine-cone' appearance to the affected area of skin.
Scale erection may be easier to detect when the fish is viewed directly from above. Where accompanied by bodily bloating (and possibly bulging eyes), this signifies a potentially lethal condition known as dropsy which is sometimes caused by a bacterial infection that may require antibiotic treatment
Where just a few scales are raised, this may be due to an injury or perhaps a localised bacterial or parasitic infection.
Curvature of the backbone which becomes kinked (snake-like curvature). Typically, scoliosis develops slowly. Possible causes include a genetic or developmental defect, infection, nutrient deficiency, or simply old age. There’s no cure.
This term describes an abnormal ‘swimming on-the-spot’ behaviour in which the fish flexes its body from side to side but without moving forward in the water. It may be interspersed with normal swimming.
Any display of shimmying may be as the result of damage being caused to the fish’s nervous system and affecting coordination. It often accompanies a bacterial infection known as columnaris and caused by Flavobacteria.
Treatment relies on diagnosing and dealing with the underlying cause, for example bacterial infection.
Slimy skin disease
Condition in which skin produces excess mucus. Affected area(s) may appear milky or greyish. Copious mucus is produced in response to an irritation as caused by skin parasites and pathogens, or adverse water conditions such as extremes of pH or chemical irritants.
Genus of protozoan (single-celled) parasites. Spironucleus are common gut inhabitants of various fish, including cichlids, but generally cause no harm. These occasionally invade tissues which can lead to disease. Spironucleus vortens has been implicated in cases of Hole-in-the-head syndrome in cichlids. Spironucleus species have also been associated with low hatching rates and poor fry survival in Angelfish breeding units. Treat with metronidazole or similar from vets.
This can have many causes, such as genetic or developmental abnormality, improper diet, or chronic stress. Chronic disease can also retard growth. In any large brood it is normal for some to remain stunted. Where a dietary problem is suspected, a complete, well-balanced diet can sometimes improve stunted individuals.
Spring Viraemia of Carp (SVC) is a highly contagious and potentially life-threatening viral disease. It primarily affects Koi and Common carp, but can also occur in other coldwater cyprinids and Wels catfish (Silurus glanis).
Although rare in the UK, SVC can be brought in on infected fish, especially those illegally imported from SVC-affected regions. The disease typically manifests in spring, above 7°C/45°F water temperature. Symptoms may include skin ulceration, bloating, loss of balance, darkening, haemorrhaging of the skin, pop-eye, and trailing faeces.
If SVC is suspected, contact a vet or Koi health professional immediately. It is a notifiable disease and there’s no chemical cure.
Affected stock may have to be put down.
The swimbladder is a gas-filled sac within the body cavity and functions primarily as a buoyancy aid. Infection, displacement or damage can lead to its enlargement, resulting in excessive positive buoyancy — fish floating at surface. It may become reduced in size, collapsed, or fluid-filled, resulting in negative buoyancy — fish sinking to bottom of tank.
Goldfish seem particularly prone to over inflation or displacement of the swimbladder, which may be due to disease, abnormal kidney enlargement and other causes.
Swimbladder disorders and the buoyancy problems they cause are generally difficult to treat.
There are some 3,400 species of these worm-like parasites known technically as cestodes and all are parasites of various animals. Of these, some 800 species parasitise various freshwater and marine fish.
Some species occur as the adult stage within the fish’s intestinal tract where they absorb ingested food from their host. An example is Khawia that lives within the intestines of carp.
Adult tapeworms are typically elongate and ribbon-like, comprising numerous segments. Some species may reach 30cm/12”. The adult has hooks and suckers for attachment to the gut wall, so preventing it from being flushed out of the host.
Other tapeworm species occur as the larval stage within the fish, typically residing within the body cavity. An example is Ligula that occurs in carp and other cyprinids and the adult worm lives in the intestines of fish-eating birds, such as gulls. Paradoxically, some tapeworm larvae are bulkier than the adult worm!
Most tapeworms have highly complex life cycles in which they must sequentially pass through two or more different hosts to complete each generation. Depending on tapeworm species, the adult may live in the gut of either a mammal, bird, or fish.
Fish may acquire tapeworms by eating an aquatic worm — Tubifex for example — or aquatic crustacean, such as a copepod, that happens to be infected with tapeworm larvae.
Because their life cycles require two or more different hosts, tapeworms are not common in farmed ornamental fish and are highly unlikely to be infectious under aquarium conditions. Wild caught fish, on the other hand, may harbour these parasites. Collectors and exporters use chemicals to purge wild fish.
Fish lightly infected — perhaps harbouring just a single worm — may exhibit no obvious symptoms. A heavy infestation of gut tapeworms can consume a lot of the fish’s food intake, resulting in it slowly becoming weakened and starved from within. The sheer bulk of several large tapeworms can cause a noticeable abdominal swelling.
In live fish, it is difficult to confirm a tapeworm infestation except by having a sample of the fish’s faeces examined professionally for tapeworm eggs. Larval tapeworms do not produce eggs.
Gut-dwelling tapeworms can be purged using medications, known as anthelmintics — an example being Praziquantel. These are available from a vet, but some may now be legally obtained without prescription from special aquatics suppliers. Traditional parasite cures —for example, whitespot cures — will not kill tapeworms.
These spend only short periods of time on the fish. An example is the fish leech (Hemiclepsis) that attaches to the skin in order to feed on blood. For much of the time, the leech lives freely in the water.
Another temporary parasite is the fish louse (Argulus) which is a type of crustacean.
The genus of protozoan (single-celled) organisms, two Tetrahymena species, T. corlissi and T. pyriformis, have been linked with disease in livebearers and other aquarium fish. They cause ‘Guppy disease’ (‘Tet disease’).
These microscopic organisms are generally free-living but, under certain circumstances, may parasitise the fish’s skin and sometimes deeper tissues.
Tetrahymena are a major health problem on some guppy farms. Congregations on the fish may result in whitish skin patches and most evident on dark fish such as Black mollies.
Affected scales may protrude outwards, resulting in localised area(s) of bristly-looking skin.
In guppies, parasites may form a ring around the eye, causing ‘spectacle eye’ disease and heavy infections can kill guppies within 24 hours. Treat outbreaks with a general skin parasite cure or whitespot cure.
Unhygienic water conditions, overcrowding, and exposure to low water temperatures have all been linked with Tetrahymena outbreaks.
These microscopic saucer-shaped protozoa occasionally attach to the fish’s skin or gills. They are more commonly encountered on wild or pond fish and may be present in large numbers on individuals already diseased or weakened. Severe outbreaks cause skin and gill damage, risking secondary bacterial and fungal infections.
Badly affected fish may show signs of skin irritation such as repeated body rubbing and, in severe cases, the fish may hang listlessly below the water surface. Treat using a commercial skin parasite remedy.
This is the common name for a neoplasia. A tumour is an unnatural growth that sometimes develops on skin or within the fish’s tissues or organs. Some types are more harmful than others.
They are generally unpreventable and incurable, but most are non-contagious.
Localised crater-like lesion on the surface of an organ or tissue. Skin ulcers appear as one or more open sores, typically red-brown with a whitish border. A deep skin ulcer may extend to the underlying muscles.
Ulcers can be caused by raised ammonia levels. In other cases, a bacterial infection is to blame. Some have a viral origin. Infected skin ulcers usually respond to anti-bacteria remedies, including herbal (Melaleuca-based) products sold for use on fish.
Those not healing properly may require antibiotics from the vet. Recuperate ulcerated fish under clean, hygienic water conditions to reduce the risk of further infections of the damaged area.
Oodinium/rust disease/gold dust disease is caused by tiny protozoa belonging to the genera Piscinoodinium (freshwater form of velvet) and Amyloodinium (marine velvet).
The parasitic stage anchors itself to the skin, fin or gill, causing irritation. The damaged skin is vulnerable to secondary bacterial or fungal infections. Gill damage can result in severe breathing problems and flared gill covers.
Fish with heavy infections — involving many hundreds or thousands of parasites — appear covered in a fine dusting of tiny spots; each being a single parasite. In freshwater velvet the spots may appear green-gold under bright light.
Affected fish tend to body rub and twitch fins and each parasite eventually exits the fish and transforms into a reproductive stage in the aquarium.
Within a matter of days numbers can increase dramatically.
Velvet disease is highly contagious and prompt treatment is necessary to eradicate parasites before they reach deadly levels. Commercial velvet and general parasite cures are on the market to deal with outbreaks.
With Piscinoodinium it also helps to darken the tank during an outbreak, as these parasites rely partly on photosynthesis for energy.
This involves the transmission of a pathogen, notably certain bacteria and viruses, from parent fish to offspring via the gametes or reproductive system. For example, a female fish with mycobacteria may pass on some of bacteria to her developing fry or eggs, such that the offspring are born (or hatch) already infected.
Viruses are primitive disease-causing organisms that live within cells of their host. Most are considerably smaller than bacteria, so cannot be seen under an ordinary light microscope — a costly electron microscope is required instead.
Numerous types of virus affect fish, causing a wide range of diseases that vary in symptoms, severity and contagiousness. These include KHV (Koi herpes virus), Carp pox virus and Lymphocystis virus.
Some viruses are highly host specific, meaning they infect only one or a few species of fish. For example, there is an iridovirus that appears to affect only Ram cichlids. Others have a broader host range, such as the fairly common Lymphocystis virus that causes harmless skin lumps on cichlids, gouramis and other ‘evolutionary advanced’ groups.
There are currently no chemical treatments to cure infections in fish – even antibiotics won’t work. In some cases, the fish’s own immune system may overpower the virus, leading to self-cure, as generally happens in Lymphocystis.
Chronic, debilitating disease in which the fish becomes progressively thinner — wasting away. Usually attributed to a mycobacterial infection.
This common and easily recognised disease is caused by single-celled protozoa that attacks skin, fins and gills.
The parasite that affects freshwater fish (tropical and coldwater species) is Ichthyophthirius. Cryptocaryon affects tropical and sub-tropical marine fish.
Parasites burrow beneath the surface of the skin causing white-grey spots — each one growing to roughly the size of a sugar grain. The mature parasite later exits the fish and forms a reproductive ‘cyst’ within the substrate. Each one gives rise to many hundreds of microscopic infective stages that swim and search for fish to infect, so repeating the life cycle.
Whitespot is potentially lethal, causing extensive skin and gill damage. Affected fish may flick fins and rub their bodies. Heavy infections may cause breathing problems — gasping and fast gill beats — and skin damage may lead to secondary infections. Badly affected fins become ragged.
These two parasites’ reproductive potential, combined with their broad host range, means that whitespot can quickly overwhelm all fish in an aquarium or pond.
Promptly treat aquarium or pond with a commercial remedy. Treat all fish, even if only a few show signs of disease. One or more repeat doses may be necessary, especially when dealing with Cryptocaryon, to ensure complete eradication.
Deal with any secondary bacterial or fungal infections with an appropriate remedy. Do not use copper-based cures for aquariums that house invertebrates. Seek advice in those instances.
Can be transmitted from animals, including fish, to humans — or vice-versa. A few types of bacteria, including species of mycobacterium, salmonella and aeromonas, have very occasionally passed from fish, or their water, to humans. Fortunately, the risk of contracting a zoonotic disease from pet fish is extremely low.
Attention to personal hygiene will greatly reduce any risk. Thoroughly wash your hands after handling fish and avoid placing unwashed hands in the mouth or eyes. Bear in mind that fish are among the safest of pets, which is why we often see aquariums in hospitals and retirement homes.
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Dr Peter Burgess, Senior Consultant of the Aquarian Advisory Service, takes us through the alphabet, looking at the common â€“ and not-so-common â€“ health matters that can affect our fish.
Dietary condition often caused by inadequate food intake or poor diet. Sometimes due to certain diseases, such as a heavy tapeworm infestation. Affected fish slowly lose body mass and muscle wastage may also occur.
Malnourished fish become emaciated and typically develop a pinched-in 'hollow' belly. As it becomes progressively thinner, the fish’s head may appear disproportionately large compared to the body.
Fish may become malnourished because they refuse to feed, perhaps due to ill-health or stress, or because they are inhibited by aggressive tank mates.
Offering the wrong types of food can also lead to malnutrition. For example, some fish — such as pike, seahorses, and the fry of many species — may only accept living foods and refuse to eat at all if only offered dead or artificial diets.
Veterinary drug used to treat skin and gill flukes (monogenean flukes). Can be delivered via the water at levels of 1 mg/l per 24-hour bath. Higher doses may be required to combat some species of monogenean. Available on veterinary prescription.
Tumour of the black pigment cells within the skin and affected fish develop slightly raised black areas on the surface.
Some platy/ Swordtail hybrids are particularly prone to melanomas which are also occasionally seen in ageing tetras. Usually lethal, but non-contagious. There’s no known cure.
Dye-based chemical traditionally used to treat fungal, bacterial and protozoal infections. Less commonly used these days, except for treating egg fungus). May destroy the biological filter bacteria.
Veterinary drug, marketed as Flagyl®. The drug of choice for treating hole-in-head (HIH) syndrome in cichlid fishes. Metronidazole combats intestinal flagellate protozoa such as spironucleus and hexamita which are implicated in HIH.
It’s also effective against certain anaerobic (oxygen-hating) bacteria.
Can be administered via the water or with the fish’s food, assuming they are feeding normally. Seek expert advice regarding dose rates and exposure times.
Not readily soluble in water so ensure the drug is fully dissolved before use.
Some experts switch to using di-metronidazole when dealing with stubborn cases of HIH.
Large group of protozoan parasites that affect various animal groups, including freshwater and marine fish.
Microsporidians are very small, spore-producing organisms that live within the cells of their host as intracellular parasites. The tiny spores (less than one-hundredth of a millimetre) may remain viable in the water for long periods, sometimes over a year.
Numerous species affect fish, perhaps the best known being Pleistophora hyphessobryconis which causes neon tetra disease. Another species, Glugea anomala, causes the small lumps or cysts we often see on the skin of wild sticklebacks. There ‘s no established treatment for microsporidial infections.
Group of parasitic flukes. Most species live on the body surfaces of cold-blooded animals, particularly fish and amphibians. They include the skin flukes, such as Gyrodactylus, and gill flukes (Dactylogyrus), both of which cause serious damage to pond and aquarium fish.
Some monogeneans are highly host-specific, affecting only one or a few fish species.
Disease causing white-greyish lesions on the mouth and they may develop into cotton-wool like growths.
Despite its common name and fungus-like appearance, this disease is caused by a bacterium (Flavobacterium columnare).
The lesions can rapidly advance and prove fatal if not treated promptly. Use a specific mouth fungus remedy or other suitable anti-bacteria treatment.
Genus of rod-shaped bacteria. Some are harmless free-living organisms, others cause disease in humans and animals. Notable species affect fishing are Mycobacterium marinum and M. fortuitum which cause wasting disease (Fish TB).
The bacteria can occur throughout the body, including skin and internal organs such as liver, spleen and kidney. Symptoms are non-specific and vary, but may include gradual weight loss, haemorrhaging and ulceration of the skin, poor coordination and pop-eye (exophthalmos).
Advanced cases may lead to curvature of the spine.
Treatment is difficult, as even multiple antibiotic therapy may fail. Permanently isolate affected populations and consider putting down badly diseased individuals. Do not breed from affected fish, as mycobacteria can be passed from parents to progeny.
Wear rubber gloves when handling suspected cases or their aquarium water as the mycobacteria can, on rare occasions, infect human skin, notably the lower hand.
Nematode worm infestations
Known commonly as roundworms, nematodes are characterised by elongate, cylindrical bodies which are non-segmented. They range, depending on species and stage, between a few millimetres to a few centimetres — just over an inch.
Many nematode species are harmless, living freely in soil or water, and some are important live foods for fish, notably the 'microworms' cultured by fishbreeders.
Others are parasites, including some 650 species known to affect various freshwater and marine fish. Most live as adults in their host’s digestive system. Some nematodes lay eggs, others give birth to live young. Their life cycle may be direct (from fish to fish) or involve two or more different hosts (fish and aquatic invertebrate such as Cyclops).
Parasitic nematodes key to ornamental fish include Camallanus and Capillaria. Low level infestations, low numbers of worms, may cause no obvious signs. Heavy infestations will consume a significant proportion of the fish’s ingested food and may cause gut damage. Badly affected fish become emaciated, lethargic and may die.
These symptoms can have other causes, such as poor diet, bacterial gut infection and other gut parasites, so confirmation of an infestation may require microscopy to check for nematode eggs within faeces. A vet or fish health expert can do this. With some species, such as Camallanus, the worms may protrude from the fish’s vent.
Treatment requires de-wormer drugs known as anthelmintics, such as fenbendazole or levamisole which can be added to the water. For fenbendazole, dose 2mg per litre for seven days and repeat twice more to complete a 21-day treatment.
Some anthelmintics are available only on vet prescription. General parasite cures from the aquarium shop are ineffective.
Neon tetra disease
This affects Neon, Glowlight and Penguin tetras, and possibly other fish such as barbs and Zebra danios. Cardinal tetras appear unaffected.
Caused by a microscopic spore-forming parasite, Pleistophora hyphessobryconis invades the fish’s muscles, but low level infections may cause no outward symptoms.
Disease is characterised in Neons by fading of colours, development of white patches on the skin, and damage to muscles (including localised muscle swelling) leading to bodily distortion and abnormal swimming. Badly affected fish become emaciated and die.
Fish may acquire the parasite by foraging on the carcass or ingesting the faeces of infected fish. There’s no widely accepted treatment, although toltrazuril from the vet holds some promise.
Permanently isolate suspected cases to reduce risks of spreading disease to other vulnerable tetras. If an outbreak occurs, avoid restocking with susceptible species (notably Neons, Glowlights and Penguins) for at least one year as the spore stage may remain viable in the aquarium for many months.
Note that colour fading and development of white skin patches in Neons and other fish can also be caused by a bacterial infection (flavobacterium bacteria), which is often accompanied by tail rot.
This is known as 'false neon disease' and can be treated with a general anti-bacteria drug.
Antibiotic, sometimes used for treating bacterial infections in fish and available as neomycin sulphate. Can be given as a prolonged bath, using 65 mg per litre. One or two repeat treatments, three days apart, may be required. This drug destroys filter bacteria, so monitor ammonia and nitrite levels during and after treatment.
Commonly known as a 'tumour', a neoplasia arises when one or more cells within the fish’s body begin to malfunction and multiply out of control. The abnormal cell mass may slowly grow to a visible lump.
Neoplasias can arise in virtually any organ or tissue and some are more harmful than others.
Those associated with the skin include the generally harmless papilloma forms sometimes seen on goldfish and other species. Potentially more serious are the pigment cell neoplasias, notably melanomas.
Neoplasias of the internal tissues may go undetected, although some grow to cause visible bulging of the body.
Certain neoplasias are triggered by viruses and can affect several fish. Very old or chronically stressed ones are more prone.
Neoplasias are generally unpreventable and there are no chemical treatments.
New tank syndrome
This term refers to a common, but largely avoidable, cause of mass mortalities in newly set-up aquariums and can also affect ponds. Many or all fish die as a result of self-poisoning, due to a build-up in the water of their toxic wastes; ammonia and its break-down product nitrite.
Poisoned fish may initially become jumpy and exhibit fast gill beats and/or surface-gulping. In acute cases, they may spin or appear otherwise disorientated due to neurological damage by ammonia.
The risk is greatest in aquariums stocked too rapidly with lots of fish; the tank and filter initially lacking adequate numbers of nitrifying bacteria that break down ammonia and nitrite wastes.
The critical period is typically within three weeks of setting up the aquarium, but this may be prolonged under coldwater conditions and its duration is influenced by other factors such as stocking density.
Stock slowly — for example, adding just a couple of small fish per fortnight in the case of a tropical aquarium.
Frequently test for ammonia and nitrite levels, perhaps every few days, during the critical few weeks after setting up. If ammonia and/or nitrite levels rise, they should be promptly reduced by partial water changes and/or ammonia-neutralising chemicals available from your aquarium shop.
Eventually, both ammonia and nitrite should stabilise to virtually zero as the filter and aquarium become adequately colonised with nitrifying bacteria — marking the end of the NTS-critical phase.
Nifurpirinol (furanace; auranace)
Synthetic antibiotic effective against a range of bacterial pathogens of fish. Can be added to the water, as in a short-term bath involving 1-2 mg per litre, up to six hours. This drug is rendered inactive by bright light and is toxic to scale-less fish, including loaches and catfishes. It is also a carcinogen, so handle with care. Available on veterinary prescription.
Ammonia wastes are broken down by nitrifying bacteria (for example, filter bacteria) into nitrite and then nitrate. This end product is mildly toxic and some species are more nitrate-sensitive than others. Nitrate levels slowly accumulate in the aquarium water and are generally kept in check through regular partial water changes or with special nitrate-removing chemicals, or filters.
Poorly maintained aquariums may have very high nitrate levels (over 100 mg per litre). Fish may be able to adapt to a gradual increase in nitrate, but are less able to withstand sudden, dramatic exposure to high levels.
Nitrate shock can occur when newly purchased fish — typically kept in low-nitrate conditions in the shop — are placed in a home aquarium containing a high nitrate level. On the second or third day after purchase they are often 'mysteriously' found dead, due to nitrate poisoning. Resident fish, on the other hand, have physiologically adapted to cope with high nitrate levels and remain 'normal'.
Ammonia wastes produced by fish are converted into nitrite by certain types of bacteria, notably those inhabiting the biological filter. Other filter bacteria convert nitrite into nitrate, but if these are absent or in insufficient numbers, then nitrite may accumulate in the water, risking harm or death.
Some species, such as Discus, are more nitrite-sensitive than others, like Guppies. In general, the nitrite level should be kept below about 0.5 mg per litre, but ideally should be zero— being undetectable using aquarium test kits.
Nitrite harms by affecting oxygen transportation by the blood. As a result, nitrite-poisoned fish suffer from oxygen starvation and exhibit fast gill beats and gasping. Their gills may turn brownish.
Check for nitrite using an aquarium test kit. A high level generally indicates that the biological filter is not working properly, or not coping with the quantity of fish. As a short-term solution, the nitrite level can be reduced by performing one or more largish water changes. In freshwater aquariums, adding sodium chloride to the water (0.1 grams per litre is sufficient and is tolerated by most fish) will reduce nitrite toxicity. These measures buy time while the underlying problem is rectified.
Genus of rod-shaped bacteria. Some cause chronic diseases in freshwater and marine fish. Important to ornamental fish, especially tropicals, is Nocardia asteroides.
Symptoms in fish are similar to those caused by mycobacteria and may include skin ulceration and discoloration, and pale nodules (granulomas) within internal organs (spleen, kidney). Infections due to nocardia are probably less common than those caused by mycobacteria, but both types of diseases are difficult to treat, even when using antibiotics. Isolate suspected cases.
Generally caused by prolonged feeding of a nutritionally inappropriate diet. This may lack one or more essential nutrients, such as an essential amino acid or vitamin, resulting in the fish being unable to grow or function normally. The diet may contain excessive amounts of a particular component (for example, vitamin, lipid) toxic to fish.
Nutritional diseases are typically chronic, perhaps taking many weeks to cause outward signs in fish. Symptoms are vague and vary greatly according to the nature of the problem, and include eye cloudiness and cataracts, skin lesions (bruising, haemorrhaging), fin erosion, spinal curvature, emaciation.
These diseases may be mistakenly attributed to other causes, such as bacterial infection, when the diet is at fault. Nowadays, the wide availability of nutritionally balanced dry diets, frozen foods, and live food cultures means that nutritional problems can largely be avoided. Commercial dry foods, such as flakes and pellets, do vary in quality between brands, so pay a little extra for a quality product.
Gross overfeeding or the feeding of poorly balanced and/or fatty diets may lead to obesity and associated health problems. Obese fish may develop an abnormally large abdomen and increased girth. There may be 'hidden' damage too, such as degeneration of the liver due to fatty diet.
Obesity is commonly seen in carp (Cyprinus carpio) raised for angling purposes for which the fish have been fast grown on fatty, inferior quality foods. Covers of carp angling magazines frequently display obese specimens held out of water, their bloated abdomens sagging under the pull of gravity.
Certain catfishes seem particularly prone, again due to excessive or inappropriate foods.
However, before placing a seemingly obese fish on a diet, consider other possible causes, such as abdominal enlargement due to developing eggs or embryos, internal infection leading to fluid accumulation in the abdomen and other tissues (dropsy, typically accompanied by raised scales); kidney enlargement disease (polycystic kidney, which can affect goldfish) or internal tumour.
Oxygen starvation (suffocation)
This life-threatening condition is caused by a lack of oxygen reaching the tissues. Fish suffering from mild starvation may go off their food but, in more severe cases, they may exhibit fast gill beats and/or gasp or gulp at the water surface. Death can occur rapidly.
The underlying causes of oxygen starvation can be grouped into two main categories:
Insufficient oxygen in the water: Low dissolved oxygen levels can be the result of overcrowding, pollution, or inadequate aeration. High water temperatures will also reduce the oxygen- carrying capacity of the water. Under such conditions, often the larger individuals, and those species that require high oxygen levels, are first to suffer. For example, Orfe within the pond will show signs of oxygen starvation before goldfish or Koi.
Gill or blood problem: Fish will be unable to extract enough oxygen from the water if their gills are badly damaged. They may be infected by bacteria, fungi, or parasites, or damaged by certain toxic chemicals in the water, such as ammonia or chlorine. High levels of nitrite in the water can lead to suffocation by diminishing the blood’s ability to carry oxygen to the tissues.
Act promptly if fish develop signs. Try and increase aeration as a short-term emergency measure. If a water problem is suspected, consider moving the fish to a spare aquarium, assuming it has suitable and safe water parameters, or perform a large water change to dilute out an offending chemical.
Perform water tests, notably for ammonia, nitrite, and Ph, and ideally for dissolved oxygen. If a gill infection is suspected, treat with an appropriate disease remedy. Seek help if in doubt.
When several or all your fish die within 24 hours, having developed breathing difficulties, then suspect a water problem rather than an infectious disease.
A type of tumour manifesting as a slow-growing flat, round, or wart-like growth on the skin or other body surface. Some papillomas can reach pea size or larger, but are mostly harmless. They are not uncommon and some species, such as goldfish, seem particularly prone. Affected fish may have one or more of these growths, but otherwise appear normal and healthy.
There’s no chemical treatment and the growths are generally best left alone. Surgical removal by a vet may be warranted in a few cases, for example where the lump encroaches on the fish’s vent or gills. Seek help if in doubt as to whether a lump is a tumour.
Serious kidney disease which commonly affects goldfish and Koi. Also known as kidney enlargement disease due to abnormal development of large fluid-filled cysts within the kidney tissue.
Affected fish develop considerable abdominal swelling which may appear asymmetrical (one side of the fish being more swollen than the other). In some cases, the enlarged kidneys displace the fish’s swim bladder, leading to buoyancy problems. Fish ultimately die from this condition.
Outward symptoms can be confused with the bloating syndrome known as dropsy. However, there is generally no scale erection that typically accompanies this.
Infection with the kidney parasite Hoferellus (a microscopic spore-forming parasite), has been implicated as the major underlying cause. In some cases, a genetic defect or kidney tumour (neoplasia) may be to blame. This condition is largely untreatable and seriously debilitated fish should be put down.
However, experimental use of the anti-parasite drugs toltrazuril and fumagillin has shown some success in combating Hoferellus infections in goldfish.
Abnormal protrusion of one or both eyes and more easily detected when examining the fish head on, or looking directly down from above. This condition is generally caused by a build-up of gas or fluid behind one or both eyes, forcing them to bulge from their sockets.
Pop-eye often accompanies the bloating syndrome known as dropsy in which the body swells and scales protrude. Underlying causes are varied, but an internal bacterial infection is frequently blamed. It requires prompt treatment with an anti-bacterial medication or antibiotics from the vet, but generally is not highly contagious.
Certain viral infections or a dietary lack of vitamins A or E have also been linked to pop-eye and unhygienic water conditions can make fish more prone.
An anthelmintic (de-wormer) and the drug of choice for treating intestinal tapeworms and monogenetic flukes (skin and gill flukes). Can be administered as a short-term bath, such as dosing 2-10 mg per litre, for up to six hours and provide good aeration. Perform one or two repeat baths, five days apart, if required.
For treating gut tapeworms, the drug can be incorporated with food, assuming the fish are eating. Use 5-10 milligrams of praziquantel per gram of fish food, given daily for three consecutive days. It is available on veterinary prescription.
Condition in which fish has breathing difficulties. Those affected typically have fast gill beats and/or gasp or gulp at water surface — the latter not to be confused with surface feeding!
Common underlying causes are:
- Insufficient oxygen in the water (environmental hypoxia), perhaps due to overcrowding, pollution or inadequate aeration.
- Gill damage caused by water conditions (chlorine or ammonia damage, exposure to extremes of pH).
- Gill infection caused by certain viruses, bacteria, fungi or parasites.
- Blood problem (high nitrite levels reducing blood’s ability to carry oxygen to tissues).
Perform various water tests (notably for ammonia, nitrite, pH and, where possible, dissolved oxygen) before considering gill infection. Consider if fish have been recently exposed to tapwater not pre-treated with a chorine remover.
Tip: Where several previously healthy fish suddenly develop signs of respiratory stress, say within 24 hours, then condition is likely due to low oxygen levels or water problem rather than infectious disease.
Group known technically as nematodes. Some are internal parasites of fish.
Dr Peter Burgess, Senior Consultant of the Aquarian Advisory Service, takes us through the alphabet, looking at the common â€“ and not-so-common â€“ health matters that can affect our fish.
Condition caused by exposure to acidic pH levels that are below the tolerance range of the species in question. A large and sudden drop in pH can result in fish developing tremors and excitable behaviour such as darting and jumping. Potentially lethal. Such rapid pH falls are more likely to occur under softwater conditions where the low mineral content of the water is inadequate to stabilise the pH.
More commonly, the pH fall is gradual, causing fish to secrete excess mucus, evident as a slimy-skin appearance. Excessive mucus production by the gills leads to breathing difficulties, gasping and rapid gill beats. Fish that are kept below optimum pH range may have poor growth and fail to spawn.
Acidosis can be prevented by routinely testing the pH and by using appropriate pH buffers. Regular partial water changes also help. Before buying fish, find out whether they are suited to the pH conditions of your aquarium.
Dye-based drug that combats certain bacterial, fungal and protozoal infections of fish. Less commonly used these days due to resistance by many common types.
Infections that are relatively short in duration, typically lasting a few hours to several days, and/or severe.
Genus of bacteria commonly found in freshwater habitats, including aquariums and ponds. Some Aeromonas species are potentially harmful to fish, causing skin bruising and reddish or grey skin ulcers. Prompt treatment is necessary to prevent the infection from becoming life-threatening.
Mild cases may respond to anti-bacterial remedies from the aquarium store. Stubborn or severe ulcerative infections require antibiotics from the vet. Overcrowding and unhygienic water conditions will render fish more prone to infections.
The digestion of proteins by fish results in the production of ammonia. Ammonia is highly toxic to fish, hence they must eliminate this waste product from their bodies by excreting it into the water. If levels of ammonia in the water get too high, the fish will be poisoned.
Ammonia damages the skin, gills and other tissues, causing a variety of symptoms that may include breathing difficulties (fast gill beats, gasping); erratic swimming and sudden darting; skin bruising (haemorrhaging) and over-production of mucus (opaque patches on the skin). The toxicity of ammonia increases with pH and with water temperature. Levels are usually kept in check by the biological filter, which harbours bacteria that break down ammonia into less toxic substances.
Ammonia poisoning is largely preventable by routinely checking levels using a test kit and avoiding overcrowding or over-feeding. Dangerous levels of ammonia must be dealt with quickly, for example by performing large water changes and/or using an ammonia-removing agent, such as zeolite. These quick-fix measures buy time while the underlying cause is addressed.
Condition caused by a deficiency of red blood cells or a lack of haemoglobin*. The gills of anaemic fish are pale, unlike those of healthy fish which are bright red. Severe anaemia may lead to breathing problems, manifesting as gasping or fast gill beats. Bear in mind that breathing difficulties are more likely due to damaged or infected gills.
Anaemia can have many underlying causes. For example, certain bacterial infections disrupt the fish’s red blood cells, causing haemolytic anaemia.
Anaemia is also caused by a significant loss of blood, known as haemorrhagic anaemia, which can arise from an injury or from viral infections such as SVC (Spring Viraemia of Carp). Heavy infestations of blood-sucking parasites such as fish lice and leeches are another cause. Feeding a poor-quality diet that lacks certain nutrients, such as pantothenic acid, may also lead to anaemia.
*Haemoglobin is a red pigment molecule within red blood cells. Its function is to transport oxygen around the blood.
Living without oxygen. Some types of bacteria are anaerobic, for example those that cause stagnant areas of gravel within an aquarium to turn black.
Chemicals that calm fish or render them unconscious, eg for surgery. Suitable fish anaesthetics include TMS (tricaine methane sulphonate) and benzocaine. Most anaesthetics are thought to possess analgesic (pain-suppressing) properties.
Drugs that combat helminth (worm) parasites such as flukes and tapeworms. Some are available only on prescription, from a vet.
A group of chemicals that can kill or inhibit bacteria and certain other micro-organisms. Natural antibiotics are produced by moulds, eg the Penicillium mould produces the antibiotic penicillin.
Nowadays, synthetic antibiotics such as enrofloxacin and oxytetracycline are used to combat bacterial infections of fish.
This often indicates a health problem, perhaps due to disease, stress (eg bullying by tankmates) or poor water conditions, including low oxygen problems. Investigate these possibilities and always perform water tests when fish go off their food. In some cases, appetite loss may be normal, for example pond fish tend not to feed during the cold winter months.
Newly introduced fish may be reluctant to feed for the first day or two until they grow accustomed to their surroundings. Sometimes the choice of food is to blame. For example, predatory fish such as gars and pikes are unlikely to accept non-living foods.
Ascites (ascitic fluid)
An abnormal accumulation of fluid within the body cavity. The build-up of ascitic fluid leads to the condition known as dropsy in which the fish’s body bloats and its scales stick out.
Ascites is generally the result of damage or infection of the liver, kidneys or other organs that play a role in osmoregulation*. The underlying cause is often a bacterial infection, but sometimes a viral or parasitic infection, or simply old age, is to blame.
This condition is often fatal and is very difficult to cure. Where a bacterial infection is suspected, antibiotics, from the vet, may sometimes be effective.
*Osmoregulation: the physiological process by which a fish maintains its internal salt-water balance.
Primitive single-celled organisms. They are microscopic, ranging in size from about 0.5 to 10 microns (one micron is one-thousandth of a millimetre).
Thousands of species inhabit aquatic environments, however only a small percentage are harmful to fish. Many perform useful roles in the aquarium and pond by consuming organic waste matter, thereby helping to keep the water clean. Important among these are the filter bacteria that break down the fish’s toxic ammonia wastes into less toxic nitrite and finally to weak toxic nitrate.
Some aquatic bacteria have a Jekyll and Hyde lifestyle in that they live harmlessly within the water or inside the fish’s gut, but sometimes cause disease if the fish is weakened, eg as result of injury or stress.
Bacteria reproduce by binary fission, in which the bacterial cell divides into two. Under optimal conditions, some bacteria are capable of dividing every 60 minutes or so, such that a single bacterium can yield millions of progeny within just 24 hours! This explains why some bacterial infections, if not promptly treated, may quickly overwhelm a fish.
Bacteria are relatively featureless in appearance, even when viewed under a high power microscope (x1000 magnification). Hence it is not possible to precisely identify bacteria simply by looking at them.
They do, however, vary in shape: many species that infect fish are rod-shaped. Others are spherical, known as 'cocci'; comma-shaped, eg. Vibrio bacteria; or spiral. Some bacteria are able to swim by waving their hair-like flagellae to propel themselves through the water.
Fish-pathogenic bacteria include various species of Aeromonas, Vibrio, Flavobacterium and Mycobacterium, to name just a few. Between them, these bacteria cause various diseases such as ulcers, fin-rot and tuberculosis.
Many common bacterial infections can be treated using liquid remedies obtainable from the aquarium store.
Serious or persistent infections may require antibiotics from a vet.
Overcrowding and unhygienic water conditions will render fish more prone to bacterial infections.
Bacterial infection of the blood. Not easy to diagnose as the outward symptoms are vague and vary according to the severity of infection and the species of bacteria involved. Affected fish are likely to be very ill and listless.
Antibiotics offer the best chance of treating this life-threatening condition.
A drug that destroys bacteria.
Balance (loss of)
Affected fish lose their ability to maintain normal swimming posture. Some may lie on their sides, turn upside-down, or float at the water surface.
Loss of balance can have many causes. A severe illness or poisoning may sometimes be to blame. In the case of fancy goldfish (such as Orandas and Moors), their stumpy body shape makes these fish prone to swimbladder disorders that lead to balance problems. The gas-filled swimbladder, which functions as a buoyancy device, may collapse, causing the fish to flounder on the substrate.
In other cases, the swimbladder may abnormally over-inflate, forcing the fish to float helplessly at the water surface. Unfortunately, swimbladder problems are hard to treat.
Air gulping is another cause of imbalance in fish: goldfish in particular may feed greedily at the water surface and take in lots of air. The entrapped air causes the fish to rise to the surface where it may stay for several hours until the gas is eventually evacuated. Air gulping can largely be avoided by briefly (couple of seconds) holding the dry food (eg flakes) in the water before releasing them, so the fish have to feed in mid-water.
Chemical used for sedating or anesthetising fish.
Black spot disease
This disease manifests as tiny black spots beneath the fish’s skin. It is caused by the larvae of digenean flukes, eg Posthodiplostomum sp. Each black spot is an individual fluke, typically 1-2 mm diameter, that has lodged beneath the fish’s skin or muscles. Its black colour is due to infiltration by dark pigment cells that are produced by the fish in response to the infection. Heavily infected fish may be covered with hundreds of black spots.
Fortunately, this disease is more unsightly than harmful.
The flukes have complex lifecycles: they must infect, in chronology, a bird, then an aquatic snail, and then a fish to complete each generation.
The necessity for a bird host means that black spot disease is non-contagious under aquarium conditions, so any affected fish do not require isolation and generally live an otherwise normal life.
Sometimes ponds that are frequented by fish-eating birds may acquire these flukes via birds’ droppings. In such cases, the parasite’s lifecycle can be interrupted by eradicating the intermediate aquatic snail hosts.
Loss of sight can arise from eye damage or eye loss, or from damage to the optic nerves or brain. In the case of damaged eyes, the underlying cause may be physical (eg damage as when a startled fish rubs against a rock) or disease. Eyes may be lost as a result of attack by aggressive tankmates. The blind fish may still be able to navigate and locate food thanks to other sensory organs such as the lateral line system that allows it to detect its surroundings.
Many species of cave fish, such as Astyanax cave tetras, are naturally blind – at least when adult. Blindness will, however, severely debilitate predatory fish such as pikes and gars that rely on sight to locate and catch prey.
Fish with recently lost or damaged eyes should be temporarily isolated and their water medicated with a bacteria remedy to reduce the risk of infection until the injury heals.
Abnormal swelling of the body, typically caused by an accumulation of fluid within the fish’s tissues. It is generally the result of damage to the kidneys or other organs involved in osmoregulation (the process by which fish maintain correct levels of salts and fluids within their bodies).
Often, a bacterial or viral infection is responsible for the organ damage, but in some cases old age, which causes organ failure, may be to blame.
With goldfish, a bloating condition known as 'Kidney enlargement disease' manifests as swelling of the flanks.
This life-threatening disease is caused by microscopic Hoferellus carasii parasites that invade the goldfish’s kidneys, causing these organs to enlarge considerably. Fish acquire Hoferellus by eating aquatic worms, eg Tubifex, that may harbour these parasites.
The closely-related Hoferellus cyprini causes similar problems in Koi. Isolate suspected cases to prevent these fish from shedding the parasite’s spores into the water.
Most forms of bloating are hard to cure, although a course of antibiotics may sometimes be effective where bacteria are to blame. There are no established treatments for Hoferellus infections, although toltrazuril and fumagillin hold promise.
A few species of parasite live within the blood of their fish hosts. Occasionally found in wild-caught fish are blood-parasitic protozoa such as Trypanoplasma and Trypanosoma sp. These parasites are transmitted by fish-parasitic leeches, so are unlikely to be present in aquarium-raised fish. Mild infections may cause no outward symptoms.
Heavily infected fish are listless and become thin, though these vague symptoms are more likely the result of more common diseases such as bacterial infections. Confirmation of blood protozoa requires the microscopic examination of a drop of blood.
There is no treatment.
Another blood parasite is the blood-fluke Sanguinicola. The adult flukes infect the major blood vessels and sometimes the heart chambers of carp-like fish, including Koi.
The fluke’s triangular eggs are released into the blood where they lodge in the fine capillaries of the gills and other organs.
The larval flukes hatch and migrate through the gill wall to reach the water. They then develop within an aquatic snail, emerging as infective 'cecariae' that must locate and penetrate a suitable fish host.
The damaging effects of Sanguinicola on the gills can be life-threatening, particularly in juveniles. Adults obstruct the blood vessels.
Treatment is problematic, however worming agents such as Praziquantel have been used with some success. The parasite’s lifecycle can be broken by eliminating aquatic snails from the system.
A rarely encountered fungus that causes gill rot in Koi and other members of the carp family.
Infected gills develop grey-brown mottling and localised erosion and fish suffer from breathing difficulties.
Outbreaks are more likely at water temperatures above 20ºC/68ºF, especially within unhygienic, overcrowded ponds. No effective treatment.
Brown blood disease
A serious condition caused by high levels of nitrite in the water. Nitrite binds to haemoglobin molecules within the blood cells, causing the blood to turn brown.
Nitrite inhibits the oxygen-carrying function of haemoglobin, hence badly affected fish may die from a lack of oxygen to their tissues.
A quick-fix measure is to perform one or more largish water changes and/or add a small amount of sodium chloride to the water (0.1 g/l) to reduce nitrite toxicity. Ensure there is adequate aeration.
These actions buy time while the underlying cause, usually a filter problem, is rectified.
Certain catfish, notably plecs and their relatives, may sometimes rest on the heater, particularly if it is positioned horizontally. This can result in skin burns should the heater come on while the fish is present, so fit a heater guard.
Burn victims should be isolated in hygienic water containing a bacteria-remedy to help prevent infection of the damaged skin.
Small (1-2 cm/½”-¾”) red-brown parasites belonging to the roundworm group. They live within the intestines of a wide variety of fishes. Livebearing species such as Guppies, platies and mollies seem particularly susceptible. It is only when one or more female worms protrude out of the fish’s anus in order to shed their eggs with the fish’s faeces that a Camallanus problem is first noticed.
Fish may acquire these worms through eating the faeces of a Camallanus-infested fish. Another route of transmission is through eating a copepod (a relative of the Daphnia water flea) that is carrying the larval stages of Camallanus.
Mild infestations may cause no obvious ill-health problems. Fish that harbour many worms, however, may become emaciated and even die. General parasite cures will not eradicate them. Instead, a special anthelmintic drug is required, such as Fenbendazole or Levamisole. Fenbendazole can be added directly to the tank as a long-term bath, redosing every seven days for a total of three weeks. The whole tank must be treated in order to destroy Camallanus in the water.
Note: The anthelmintic Ivermectin, which is used to treat cattle parasites, is not suitable, being toxic to fish.
These parasites are types of roundworm. They have very thin hair-like bodies reaching 5 mm - 2 cm/¼”-¾” in length, depending on the species.
Capillaria reside within the intestines of various fish, including Discus and Angels, particularly wild-caught specimens. The adult worms shed their eggs with their host’s faeces.
Mild infestations cause no obvious symptoms, however heavy worm burdens can result in appetite loss and emaciation, leading to death. Capillaria-infested fish may darken in colour – as observed in Discus. Affected fish produce only small quantities of faeces that appear abnormally thin and translucent.
Under aquarium conditions, fish acquire these nematodes by accidentally eating the larval stages that are shed into the water by infested tankmates. Tubifex worms are also capable of carrying Capillaria. Treatment requires a special anthelmintic drug such as Fenbendazole, Levamisole or Piperazine. Depending on the chosen drug, the anthelmintic is either mixed with the fish’s food or added to the water. Isolate infected fish to avoid them passing on their nematodes to others.
Whitening of the lens of the eye, causing impaired vision. One or both eyes may be affected.
In large fish, it may be possible to see the abnormally opaque lens beneath the transparent pupil of the eye – a strong hand lens helps.
Do not confuse this with clouding to the outer surface of the eye, which may indicate a bacterial or fungal infection.
Cataracts have various causes, including old age and exposure to water temperatures that are well below the fish’s optimum range.
Poor diets that lack certain essential nutrients (eg riboflavin, manganese or zinc) can also lead to this eye condition.
Additionally, cataracts can stem from long-term exposure to strong UV irradiation, as may occur when outdoor fish are kept in shallow ponds that lack shade.
Infection with the eye-fluke, Diplostomum, can also lead to cataracts.
Cataracts in fish are incurable.
Common name for the relatively harmless skin disease known as Lymphocystis. It’s caused by a virus.
Microscopic heart-shaped parasites that infect the skin and gills of fish. More common in pond fish at very low water temperatures, below 10ºC/50ºF. Treat with a skin parasite remedy, added to the whole pond.
An infection that persists for a long time – weeks, months or years.
Single-celled parasites that are typically covered in numerous hair-like structures known as cilia, which are used for movement. Most ciliates are microscopic in size.
Several important skin parasites of fish belong to this group, including: Ichthyophthirius (whitespot parasite), Trichodina, Chilodonella, Tetrahymena, Brooklynella and Uronema.
Condition in which the fins, notably the dorsal and anal, are held tightly to the body, and the tail fin may not be spread out normally. If a fish clamps its fins for most or all of the time, this generally indicates ill health. Fish that are stressed or victims of attack often exhibit clamped fins. Brief bouts of fin clamping, however, may be normal, and is used by some fish as a means of communication.
If many fish within the aquarium or pond show this condition, then investigate for a water problem or widespread disease (such as a bacterial infection or outbreak of skin parasites).
Whitish film or growth covering part or all of the eye surface. It can affect one or both eyes. Often, only a single fish is affected.
This condition has many causes. For example, a bacterial infection of the eye might be to blame. In some cases, it is due to a fungus infection that typically manifests as white-grey fluffy growths that project outwards from the eye.
In many cases, an underlying water problem, eg poor hygiene, is a contributory factor. Feeding a poor quality diet that lacks certain vitamins, eg vitamin A or C, can also lead to cloudy eye.
Treatment involves making any necessary improvements to the water conditions or diet, or medication of the water with a bacteria or fungus remedy.
If just one or a few fish are affected, they can be treated in isolation.
A potentially serious bacterial disease. Caused by Flavobacterium columnare, formerly known as Flexibacter columnaris. Flavobacterium infections manifest in many ways, including the condition known as mouth fungus.
In some cases, this bacterium targets the gills, skin or muscles. Flavobacterium columnare also cause tail rot in which the tail fin erodes to the base, and may rapidly progress to the fish’s body, causing a white-pinkish discolouration of the infected tissue.
Adverse conditions such as poor water quality, stress or overcrowding can make fish prone to columnaris disease. Flavobacterium infections may prove fatal if not treated at an early stage with a commercial bacteria remedy. Advanced or stubborn cases require antibiotics from the vet.
A blue crystalline chemical that is sometimes used to eradicate skin parasites in marine and freshwater fishes. It is highly toxic to certain invertebrates.
Ingestion of faeces. Many fish engage in this unpleasant feeding behaviour. Fish can become infected with certain parasites, eg Camallanus worms, and bacteria, eg mycobacteria, as a result of feeding on the faeces of other infected fish.
Hormone found in the blood of fish and other animals. The levels of cortisol increase with stress. High cortisol levels reduce the fish’s immune defences, hence badly stressed fish are more prone to infections.
Genus of parasites known commonly as gill flukes. Dactylogyrus live on the surface of the fish’s gills, but occasionally migrate to the surrounding skin. They rarely exceed 2 mm in length hence are invisible to the naked eye. These parasites possess sharp hooks that abrade and damage the gills, causing their host to suffer breathing difficulties.
Badly affected fish may exhibit fast gill beats, gasping at the water surface, and sometimes flared gill covers. Heavy infestations are life-threatening. The fluke-damaged gills are prone to secondary bacterial and fungal infections.
Dactylogyrus outbreaks can be treated using a proprietary fluke remedy that is added to water. They lay eggs that are resilient to chemical attack, hence repeat treatments may be necessary to destroy the young flukes as they hatch.
Common deformities in fish include bent backbones, stumpy bodies, misshapen heads, curled gill covers or missing fins. Deformities can have many causes and may affect the fish at any stage in its life.
At birth/hatching: Within a brood it is normal for a few individuals to be deformed in some way. Their chances of survival depend on the nature of the deformity. In the wild, survival is less likely, due to the increased risk of predation and other selective pressures. Where a significant proportion of the brood is deformed, say over 5%, this could indicate a genetic defect in one or both parent fish, or adverse environmental conditions under which the eggs or fry were raised.
Genetic defects are often the result of in-breeding. Adverse environmental conditions that can cause abnormal development of eggs or fry include low oxygen levels, extremes of water temperature, overcrowding and high levels of heavy metals, eg cadmium.
Studies on cultured food-fishes have revealed that nutritional deficiencies in the broodstock (especially the female fish) can cause fry abnormalities.
Deformities in later life: These can be caused by disease, injury or tumours. Certain chronic diseases, such as mycobacterial infections, weaken the fish’s backbone, leading to abnormal body curvature.
In Koi, a disease caused by tiny parasites (Myxobolus sp) causes a pronounced swelling around the face and gills, giving it its common name: ‘frog-face’ disease. Physical injuries may lead to backbone fractures, resulting in the fish – if it survives the trauma – having a bent back. Large tumours of the skin or internal tissues can result in a misshapen or lop-sided body.
Prevention and treatment: Unfortunately, most deformities in fish are impossible to rectify. Preventative measures rely on good fish husbandry: optimal water conditions, a disease-free environment and a healthy diet.
In-breeding defects can be largely avoided by occasionally introducing unrelated fish to the breeding stock to refresh the gene pool.
Genus of fungus-like parasites. One species, Dermocystidium koi, affects goldfish and Koi, causing smooth raised lumps to develop on the skin or fins. The lumps eventually burst, resulting in open sores that will heal.
Dermocystidium is contagious but fortunately not common. No known chemical cure.
Large group of parasitic flatworms. Some are parasites of fish, such as the eye fluke, eg Diplostomum, and blood fluke, Sanguinicola.
Potentially fatal condition in which the fish’s body swells up. It is caused by an abnormal accumulation of fluid within the body and is often accompanied by raised scales and sometimes pop-eye. In addition to their bloated appearance, affected fish may become sluggish and go off their food.
Dropsy is generally the result of damage or infection of the kidneys or other organs that play a role in osmoregulation, or the internal salt-water balance. Internal infections with certain types of bacteria and viruses, eg Spring Viraemia of Carp virus, can lead to dropsy. Some internal tumours, or simply organ failure through old age, can also give rise to this condition.
Dropsy can be difficult to treat partly because it has many underlying causes, some of which, eg internal tumours, viral infections and organ failure, are incurable. Also, by the time the fish develops signs of bloating, severe internal damage may have already occurred. Hence, over-the-counter remedies for dropsy cannot be guaranteed to work in all cases. Antibiotics from the vet offer the best hope in situations where a bacterial infection is suspected.
Technical term for "egg bound" in which a female fish is unable to release her mature eggs. This condition can arise if there are no adult males for the female to spawn with, or if the water conditions are unfavourable, eg a cold spring or summer may inhibit spawning in pond fish. Generally, dystocia is not harmful and the retained eggs may eventually be reabsorbed.
A parasite that lives on the surface of its host, eg on the skin, fin or gill surface. Examples are the skin flukes such as Gyrodactylus and various skin-parasitic protozoa including Trichodina, Chilodonella and Ichthyobodo.
This fungal condition manifests as grey-white fluffy growths that project outwards from the egg surface. It is caused by various aquatic moulds, such as Saprolegnia, which can also cause fungus problems on fish. Infertile eggs (which typically turn white) are particularly prone to fungus attack. However, fertile eggs can also be affected, risking death to the developing embryos within.
Fish that practice parental care, eg cichlids, routinely clean their eggs to reduce the risk of fungus attack.
Over-the-counter fungus medications, such as methylene blue, can be added to the egg-incubation aquarium as a means of prevention. Warning: methylene blue destroys the filter bacteria!
Certain diseases or poor diet can cause fish to lose body weight and become progressively thin. Emaciation often presents as a hollow belly in which the fish’s abdominal region looks pinched in, sometimes with a concave profile.
Common causes of emaciation include: dietary deficiencies, feeding incorrect foods, chronic loss of appetite, chronic infections such as caused by mycobacteria (fish TB), tapeworms or nematode worm infestations of the gut.
A parasite that lives inside its host, eg in the gut; within the internal organs; muscles or blood. Examples are the gut-dwelling tapeworms and the skin or muscle-dwelling digenean flukes. The whitespot organism (Ichthyophthirius) is also an endoparasite because it lives just beneath the skin surface.
Synthetic antibiotic belonging to the quinolone group. Marketed as Batril®. Considered a useful treatment for certain bacterial infections in ornamental fish. It can be given via the water or incorporated with the fish’s food.
Genus of single-celled protozoans. Normally free-living, these tiny, sessile (immobile) organisms sometimes attach to the body of fish, particularly ‘hard’ surfaces such as the fin rays.
For example, Epistylis may colonise the tips of the pectoral fins of catfishes, including Corydoras.
Although not true parasites, Epistylis may elicit an inflammation response by the fish which sometimes leads to localised ulceration that is vulnerable to bacterial infection.
A large colony of Epistylis appears to the naked eye as a small tuft of growth on the fish, such that it can be mistaken for a fungus infection.
Under the microscope, however, Epistylis reveals its characteristic cylindrical or bell shape and its long stalk for attachment: this contrasts with the branching root-like structure of fungus.
Unhygienic water conditions favour the proliferation of Epistylis. Treat affected fish with a general skin parasite cure, for instance, a whitespot cure.
Genus of parasites, comprising over 100 species. They are primitive crustaceans (distant relatives of crabs and shrimps) that invade the body surfaces of various freshwater and marine fish. They range in length from 1.5 to 6 mm. One important species is Ergasilus sieboldi (the gill maggot) which infests the gills of cichlids, the carp family and certain other fish.
Ergasilus sieboldi is rarely a problem under aquarium conditions, being more commonly encountered in pond fish. Infestations of the gills can be life-threatening, causing the fish to suffer breathing difficulties, manifesting as fast gill beats, gasping and surface gulping.
Specific anti-crustacean treatments, eg from the vet, are required to eradicate them.
Antibiotic administered with the food or via the water. Warning: erythromycin can destroy the biological filter bacteria, and prolonged treatment may cause kidney damage in fish, as shown with salmonids.
Abnormal protrusion of one or both eyes. This condition, which can have many causes, is known commonly as 'pop-eye'. This will be covered in more detail under the entry 'Pop-eye'.
Eye fluke (Diplostomum)
As its common name suggests, this tiny worm-like parasite invades the fish’s eyes, sometimes causing impaired vision, even total blindness.
Diplostomum has a complex life-cycle in which the parasite must sequentially infect a bird, an aquatic snail and then a fish in order to complete one generation. The involvement of birds (notably gulls, which harbour the adult flukes in their guts) mean that Diplostomum is generally only a problem in pond-reared or wild-caught fish.
The larval flukes that are shed by infected water snails must locate a fish and penetrate its skin. Once inside the fish, they migrate via the blood system to the eye.
Using a strong magnifying glass, the young flukes of 0.5 mm long can sometimes be seen as opaque blobs within the fish’s eye. Affected fish may have one or more flukes in one or both eyes.
Diplostomum infections are difficult to treat, but fortunately are not very common and only rarely life-threatening.
One method of prevention is to eliminate all aquatic snails from the pond – easier said than done – in order to break the fluke’s life-cycle.
The eyes of most fish are similar in structure to human eyes, and they share our ability to see in colour. The lack of eyelids in bony fish, as compared to sharks, means that the eyes have no protection against the environment.
Eye problems in fish include bulging eyes (exophthalmia), cloudy eyes and various physical injuries.
- Infectious diseases of the eyes: Fortunately, very few disease-causing organisms specifically target the eyes of fish. One notable exception is the eye fluke that spends part of its lifecycle as the larval stage within the eye lens and eye fluid.Certain surface-dwelling parasites, such as the whitespot parasite, Ichthyophthirius, and skin flukes, Gyrodactylus, sometimes settle on or crawl over the eyes, causing inflammation. Under certain circumstances, water moulds (eg Saprolegnia fungus) establish on the eye surface, causing cotton wool-like growths. Various types of bacteria, including Aeromonas species, may cause eye problems including pop-eye. If left untreated, eye infections can lead to reduced vision or total blindness. Fortunately, visually impaired fish retain some ability to navigate and locate food, thanks to their other sensory systems: these fish may, however, require isolation otherwise they could lose out at feeding times if kept with active tankmates. Mild eye infections can usually be treated with a suitable remedy, eg fungus or bacteria remedy, added to the water. Stubborn bacterial infections, including some cases of pop-eye, may require antibiotics from the vet.
- Non-infectious diseases of the eyes: Many eye problems in fish stem from unhygienic water conditions or poor diet. Exposure to very low water temperatures may damage the proteins within the eye, leading to clouding of the lens. Similarly, exposure to strong sunlight, such as when outdoor fish are held in shallow ponds that lack shade, can lead to cataracts. Dietary-related eye problems may arise if the fish is given poor-quality foods that lack vital nutrients important for eye development and function. For example, a dietary deficiency of vitamin D can lead to pop-eye. Where the eyes are damaged, for instance via cuts or grazes such as caused by handling or net injuries, the addition of a broad-acting bacteria remedy will help prevent infection while the eye heals.
Fatty liver disease
Nutritional disease. Often linked to feeding diets containing saturated fats such as fatty red meats. Within a warm-blooded animal, these saturated fats are in their liquid state, making it easy for the animal to process and store them in the liver. But if fed to fish, these fats remain solid within the fish’s relatively cold body (this applies to tropical fish also) making it difficult for the fish to properly digest and store them. As a result, the fish’s liver may be damaged and its many important functions, such as glycogen storage, impaired.
Other causes of fatty liver degeneration include dietary deficiencies, for instance from foods lacking in methionine or certain fatty acids. Feeding diets containing rancid (oxidised) fats can also cause liver damage.
Fatty liver problems generally go undetected as the condition causes no obvious outward signs. Liver damage will, however, affect the fish’s general health and growth and is potentially life-threatening. This condition is preventable by feeding only quality fish foods that are stored correctly. Avoid giving fish animal meats or other foods containing animal or dairy fats, eg burgers, corned beef, sausages, hams, cheeses, biscuits and the like.
Drug used to treat certain roundworm infestations of the gut. Fenbendazole is one of the drugs of choice for treating Camallanus gut worms that sometimes affect livebearers, eg Mollies, Platies and other fish. Can be delivered via the water as a long-term bath, eg 2 mg/l added on days 1, 8 and 15, or incorporated with the fish’s food.
A harmless benign tumour, composed mostly of fibrous tissue. Very uncommon. Skin fibromas appear as raised lumps, but can easily be confused with other more common types of skin tumours, eg papillomas, and other causes. No treatment and generally these are best left alone.
Erosion of the fin. This condition can affect any fin, however the tail fin seems more prone to this disease in which case it is specifically referred to as ‘tail rot’. Initial signs are whitish areas appearing on the fin, or there may be whitening and erosion of the fin edge, giving a ragged appearance. As the disease progresses, the fin membrane rots away, leaving the fin rays exposed. With tail rot, the infection may spread to the adjacent body, causing the affected tissue to become very pale, sometimes with a pinkish blush. Advanced tail rot causes the fish swimming difficulties and is life-threatening.
Various types of bacteria have been linked with fin rot, in particular Flavobacterium columnare, formerly known as Flexibacter. These bacteria tend only to attack fish that have a weakened immune system or those that have already sustained fin damage, perhaps due to injury or parasite attack. Unhygienic water conditions also render fish more vulnerable to fin rot. Transportation stress is another contributory factor, which is why outbreaks of fin rot are not uncommon in recently imported stock.
Fin rot is generally curable if caught early, before it spreads to the body. Treat with a general bacteria remedy or fin rot cure. With advanced infections that involve the body, even the most effective treatments, such as antibiotics, cannot be guaranteed to save the fish. Fin rot is not highly contagious and often only a single fish is affected. It is, however, wise to isolate affected fish and treat them under very hygienic conditions. Preventative measures rely on providing fish with optimal water conditions and minimal stress.
Note: Some fish possess fins that normally appear tattered or frayed. This is particularly the case with adult males of certain species, such as the swordtail characin, Corynopoma riisei, and Arulius barb, Puntius arulius.
Certain cultivated varieties of fish have been selectively bred for their ragged fins, a recent example being the Crowntail fighting fish, Betta splendens.
It is normal for fish to occasionally twitch or flick their fins, perhaps in response to a transitory irritation or as means of communication. However, when fin twitching occurs frequently, this can indicate infestation with skin parasites, such as Trichodina, Ichthyophthirius or skin flukes, to name a few, particularly if accompanied by frequent rubbing of the flanks against submerged objects, a behaviour known as 'flashing'.
Poor water quality can also make fish flick or twitch their fins, hence water tests should be carried out as part of the investigation.
Group of parasitic flatworms. They are fairly large multi-celled creatures, the majority ranging between 0.5 and 3 mm long. Many flukes are parasites of fish. Some target the fish’s skin, fins or gills, whereas others live within its body or blood. There are two main groups of flukes: the monogeneans and the digeneans.
Monogenean flukes pose the greatest health risks to aquarium and pond fish, examples being the skin flukes, eg Gyrodactylus species, and gill flukes, eg Dactylogyrus species. They can be highly contagious. Various disease remedies are available for dealing with outbreaks of skin or gill flukes.
Digenean flukes that occasionally affect fish are the eye-flukes, eg Diplostomum, and blood flukes, notably Sanguinicola. Digeneans have complex lifecycles that may include a bird and an aquatic invertebrate, eg aquatic snail, as well as a fish. Hence, digenean infections are more commonly encountered in wild or pond-raised fish.
Most digenean fluke infections are untreatable, but fortunately are rarely life-threatening and are generally non-contagious under aquarium conditions.
Fish louse (Argulus)
Blood-sucking skin parasite characterized by its disc-like shape and visible size, reaching 1 cm/1/2” in diameter. Argulus is not a true louse but a primitive member of the crab family Crustacea. There are several species of Argulus, the most common being Argulus foliaceus. They can affect a wide range of fish species but are mostly encountered in ponds rather than aquariums. Argulus are known as temporary parasites because they spend only some of their time attached to the fish’s skin in order to take a blood meal. At other times they live freely in the water.
Despite its large size, Argulus can appear well camouflaged against its host’s skin, due partly to its semi-transparent body: it can be mistaken for a partly detached scale. Heavy infestations, which are uncommon, may cause white patches on the fish’s skin. The parasite’s feeding wounds develop into small red spots that can become infected.
Badly infested fish exhibit listlessness, anaemia, and loss of appetite. Where Argulus is established in the pond, outbreaks tend to occur in spring and summer. Individual Argulus can be carefully removed from the fish using tweezers. Special anti-crustacean treatments, from a vet, are required to fully eradicate the adult and larval stages from the pond.
Group of single-celled protozoa. Many are harmless free-living organisms, but some parasitic species affect fish. They possess one or more whip-like structures, known as flagellae, that aid swimming. Important examples are the skin-parasitic flagellates that cause velvet disease in freshwater and marine fishes (caused by Piscinoodinium and Amyloodinium parasites, respectively). Others, such as the trypanosomes, parasitise the fish’s blood instead.
The gut-dwelling Hexamita and Spironucleus flagellates occasionally cause disease in various fish, including hole-in-the-head disease in cichlids. Over-the-counter treatments are available for dealing with velvet disease. Internal flagellates are more difficult to treat, however the drug metronidazole, available from the vet, is used to cure hole-in-the-head.
Behaviour in which the fish rubs its body, usually its flanks, against a submerged object such as a rock, stone, or plant stem. In the wild, when the fish rolls on its side to rub itself, this may cause a flash of sunlight to reflect off its silvery flanks – hence the term “flashing”. Repeated flashing often indicates a skin irritation, such as caused by skin parasites, eg skin flukes, whitespot parasites, Trichodina, etc.
Formerly known as Flexibacter, these can cause serious skin and internal infections in aquarium and pond fish, and outbreaks are more likely at water temperatures above 15ºC/60ºF.
They are a major cause of fin rot whereby one or more fins, typically the tail, erode away — and also cause mouth rot.
Skin infections may lead to localised bruising and, where the gills are involved, can cause respiratory problems.
Flavobacterium look distinctive under a powerful microscope as long, thin, rod-shaped organisms that tend to congregate in stacks. Individual bacteria glide against each other within the stack, so are sometimes called 'gliding bacteria'.
Over-the-counter anti-bacterial treatments are available for mild cases, including fin rot and mouth fungus, but stubborn or serious infections may require antibiotics from the vet.
A solution (37-40%) of formaldehyde gas, this is traditionally used to treat skin and gill parasites, (eg whitespot and Trichodina protozoa and flukes). It also has slight anti-bacterial activity and is sometimes used in combination with malachite green, notably for treating whitespot, Ichthyophthirius.
Formalin reduces oxygen levels in water, so ensure good aeration during treatment. It is potentially toxic to fish and aquatic plants, so use with care and never overdose.
Fish species vary in sensitivity to Formalin and contact with human skin must be prevented. Wash it off thoroughly and seek medical advice if eyes are affected.
Various aquatic fungi or water moulds are capable of infecting freshwater fish. The best-known example is Saprolegnia fungus which forms white-grey cotton wool-like growths on the body surfaces of fish as well as on eggs. Achlya and Aphanomyces are other water moulds causing similar symptoms.
Water moulds rarely attack uninjured, healthy fish, so address any underlying cause, (eg physical injury, parasite damage or poor water conditions) in addition to treatment.
Various fungus treatments are available, including salt (for salt-tolerant fish) and botanical formulations (eg Pimenta extracts). Being salt-intolerant, water moulds are not a problem in marine systems.
Other fungus-like pathogens of fish include Branchiomyces, which occasionally affects pond fish, notably carp, causing gill damage and breathing difficulties. Dermocystidium is another fungus-like organism which manifests as nodular swellings on skin and fins. There are no known chemical cures for either of these organisms.
None of the above organisms are true fungi, but they possess fungus-like characteristics — namely branching, thread-like filaments (hyphae) and tiny spores. To add to the confusion, mouth fungus, which causes the fish’s mouth to erode, is actually a bacterial disease and generally caused by the Flavobacterium species.
Gas bubble disease
Potentially fatal, similar to 'the bends' among divers, and characterised in fish by small gas bubbles (emboli) varying in size within the skin, eyes and blood. Affected fish may become lethargic, but often show no other symptoms. Cause is supersaturation of gases, notably nitrogen, within the water and can occur when cool, gas-rich water is suddenly heated, as when a new aquarium is filled with cold water which is quickly warmed to operating temperature.
It can also arise from leaks within high-pressure pipework or connectors (eg those serving pumps and filters), causing air to be sucked into the system. If suspected, immediately increase aeration to help drive off excess gas.
There is no specific treatment for affected fish, but less serious cases may recover if removed from the conditions.
Illustrated by abnormal behaviour involving laboured and/or rapid opening and closing of the mouth, in many cases at the water surface. This reflects a breathing problem and is usually indicative of oxygen starvation.
Among several possible causes a lack of oxygen is often blamed, perhaps due to fish overstocking, pollution, and/or inadequate aeration.
Another cause is a gill infection, commonly due to parasite or bacteria attack. Chemical damage to gills — for example, due to exposure to high levels of ammonia wastes or chlorinated water — can also cause gasping.
Suspect a water problem (eg low oxygen levels or chemical poisoning) when several previously healthy fish suddenly gasp, before considering gill infection. Gasping should be investigated immediately, otherwise the fish may die, and ideally aeration increased as soon as possible.
A quick fix for pond fish involves running a hose to the pond and spraying the surface to force air and oxygen into the water. Increased aeration will help while the underlying cause is investigated and remedied.
The common name for gill-parasitic crustaceans belonging to the genus Ergasilus.
Gills perform several functions, including respiration, excretion and osmoregulation (the regulation of internal salts and water). Any damage or disease is therefore potentially life threatening.
As gills are in constant contact with water they are directly exposed to any harmful chemicals within it. Their rich blood supply and ease of access also makes them a target for various parasites and pathogens.
Problems that can affect aquarium and pond fish include:
Damage by water-borne poisons or toxins: Gills can be harmed by high levels of ammonia wastes and chlorine and chloramine disinfectants in untreated tapwater. Their protective surfaces may become stripped if exposed to soaps and detergents, so never use these products to clean aquariums, décor or submersible equipment.
Avoid immersing bare metal objects in the aquarium or pond as exposure to high levels of heavy metals (notably zinc, copper, mercury, cadmium and lead) can also harm gills.
Many insecticides and herbicides can damage gills and other organs. Applying garden chemicals near the pond, especially on windy days, could allow tiny droplets into the water and poison the fish.
pH damage: Fish vary between species in pH tolerance; a particular value may be healthy and optimal for one type but damaging to the gills and other organs of another. In many species gills may become irritated and damaged if the pH becomes very acid, below about pH 5.5, or very alkaline, above pH 9.0.
Gill infections: A wide range of organisms infect gills. They include certain viruses (eg Koi herpes), bacteria (such as Flavobacterium which causes bacterial gill disease in pond fish), fungi (eg Saprolegnia), parasitic protozoa (eg Ichthyophthirius — the cause of whitespot), Piscinoodinium — velvet disease (Trichodina), flukes (Dactylogyrus — gill flukes) and crustacean parasites (eg Ergasilus — gill maggots).
Affected fish may exhibit laboured and/or fast opening of the mouths and gill covers. They may remain at the surface, gasping and gulping.
Remedial action: First perform water tests (eg pH, ammonia levels) before considering gill infection — and refer to the section on gasping for problems relating to low oxygen levels.
Look for signs that could point to gill parasites or gill pathogens. For example, many gill parasitic protozoa also attack the skin, causing repeated body rubbing and sometimes other symptoms (eg white spots).
Treat gill infections with an appropriate remedy or, if in doubt, seek professional help.
Gold spot disease
Alternative name for freshwater velvet disease. Caused by skin parasites of the genus Piscinoodinium, these contain chlorophyll pigment for photosynthesis, which gives them a golden colour when viewed in direct light — hence 'gold spot' disease.
Velvet disease will be covered in more detail under its own A-Z entry.
These manifest themselves as lumps, cysts, spots, or other swellings. They are usually noticed only when occurring on the body surface, although internal growths can also occur.
Some skin growths are the same colour as surrounding skin, while others have contrasting pigmentation (cream, white, pink and red, for example). Their shape, texture and ultimate size will vary according to the underlying cause.
Many abnormal skin and fin growths are harmless, but some are potentially life-threatening, so properly identify them to gauge their severity. If in doubt, have the affected fish examined by a vet or fish health professional.
Causes of abnormal growths include:
Fungus infections: Growths appear as white-grey cotton wool-like tufts that stick outwards from the body surface. Treat with a fungus remedy added to the water.
Parasite cysts: Certain parasites cause raised growths on the skin and/or fins. For example, whitespot parasites (Ichthyophthirius in freshwater, Cryptocaryon in marine) appear as sugar-grain-sized white cysts just under the skin.
In Koi, a relatively harmless but untreatable disease caused by Dermocystidium parasites manifests as raised lumps on the skin or fins, and sometimes the gills. Each lump can become pea-sized (up to 1cm/0.4” across) and eventually burst, releasing tiny spores into the water. Over-the-counter treatments are available for eradicating many common skin parasites.
Tumours: More correctly known as neoplasias, these occur when one or more cells within the body malfunction and begin to grow and multiply out of control. The abnormal cell mass may ultimately grow to a visible lump of a size, shape, colour and texture depending on the type of cells involved. Typically, tumours grow slowly and in many cases the fish appears otherwise normal and healthy.
Most tumours are best left alone and there are no chemical treatments. In exceptional cases, a vet may decide to remove a tumour on the skin or fins, particularly if it interferes with the fish’s vital functions; for example, where it encroaches on the vent or mouth.
Bacterial granulomas: A granuloma is a non-cancerous growth caused by chronic inflammation.
Several types of bacteria, notably mycobacteria and mocardia, may cause granulomas of the skin. These typically also invade internal organs and tissues, making affected fish appear weak and in ill health, and they may die if untreated.
Treatment is problematic. Antibiotics from the vet generally offer the best hope, but even these prescription-only drugs may fail.
Wherever possible, permanently isolate the affected fish. Assess overall aquarium/pond hygiene as dirty water conditions will render fish more susceptible to bacterial infections.
Viral growths: Relatively harmless viral diseases, such as lymphocystis and carp pox, manifest as white-pale pink lumps or waxy growths on skin and fins. There is no chemical cure but, in many cases, the fish’s immune system eventually overpowers the virus, causing the lumps to disappear in time.
Genus of stumpy, worm-like parasites known commonly as skin flukes. Gyrodactylus rarely exceed 1mm/0.04” so are undetectable to the naked eye. They parasitise the surface of the fish’s skin and sometimes the gills where they feed and breed, giving birth to live young.
There are numerous species of freshwater and marine gyrodactylus, each with its specific range of fish hosts, and they possess sharp hooks to help them attach to fish and abrade skin.
Affected fish may repeatedly rub their bodies against submerged objects, such as rocks and plant stems, to ease the irritation.
Fish also rub in response to skin parasitic protozoa, so microscopic examination may be needed to confirm whether the problem is due to skin flukes or protozoa. Heavy infestations are life threatening and the fluke-damaged skin is prone to secondary bacterial and fungal infections. Gyrodactylus outbreaks can be treated using a proprietary fluke remedy added to the water.
Condition in which blood escapes from the blood vessels. This can arise if the vessels become leaky, possibly due to infection, or physically rupture as a result of injury.
Skin haemorrhages appear as areas of bruising and a bacterial or viral infection is often to blame. Where bacteria are suspected, treat with a bacteria remedy. Antibiotics may also be required. Viral haemorrhaging is untreatable.
A lack of vitamins A, B1, B2, or C can lead to haemorrhaging, but this is a less common cause.
Group of viruses. Some cause disease in fish, examples being Koi Herpes Virus (KHV) and the Fish Pox (Carp Pox) virus. Herpes viruses vary in pathology and there are no chemical treatments for viral infections.
Genus of protozoan (single-celled) parasites. Some species infect the intestines and other internal organs. Hexamita has traditionally been implicated in Hole-in-the head syndrome (HIH; see later entry) that affects certain cichlids, but it now seems that Spironucleus, a closely related protozoan, is the true culprit.
Genus of spore-forming protozoan parasites. One species, Hoferellus carassii, is responsible for kidney enlargement disease in goldfish. Affected fish develop abdominal swelling, often more pronounced on one side (unilateral). This condition may be confused with dropsy in which the swelling is generally more even (bilateral). There may be accompanying loss of balance and listlessness. It is potentially fatal and there’s no established treatment.
Potentially fatal condition affecting Discus, Angelfishes, and certain other South American cichlids. In affected fish, the sensory pores of the head and/or lateral line may become enlarged and pus-filled. The fish may turn dark and lose appetite, and their faeces may be white and stringy. The underlying cause(s) are unclear.
HIH is commonly attributed to infection by flagellate protozoa (notably Spironucleus species). Other factors implicated include certain bacterial infections, nutritional deficiencies and lowered immunity.
Over-the-counter remedies are ineffective against Spironucleus. The drug of choice for this and HIH is metronidazole, obtainable on veterinary prescription. It is given as a bath and/or mixed with the food. Metronidazole also has anti-bacterial activity.
Use Di-metronidazole in stubborn cases where metronidazole appears ineffective.
Helminths are primitive worm-like organisms. Some species are free living, but most are parasites of various animals, including fish. Examples are various flukes, tapeworms and nematode worms that can cause disease in aquarium and pond fish.
Some helminths attach to the fish’s body surfaces, notable examples being the skin and gill flukes, while others, such as tapeworms and eye flukes, reside within the body. Helminths harm in many ways. For example, their potentially life-threatening skin and gill flukes possess sharp hooks and suckers that help them grip the fish.
These physically damage the fish’s skin or gills and render them vulnerable to secondary infections, such as those caused by bacteria.
Generally less serious are the ribbon-like tapeworms that live within the fish’s gut or body cavity. Nevertheless, a heavy tapeworm infestation can debilitate and weaken the fish.
Some helminths have complex life cycles in which the parasite must sequentially infect different types of animal host (a bird, then an aquatic snail, then a fish) in order to complete one generation.
Many ecto-parasitic helminths (skin and gill flukes) can be treated using commercial over-the-counter remedies.
Eradication of internal helminths (gut tapeworms) generally requires drugs known as anthelmintics, examples being praziquantel, mebendazole and fenbendazole. Many anthelmintics are obtainable only on prescription from a vet.
Breaking the helminth’s lifecycle, such as eliminating aquatic snails that may harbour the parasite’s larval stages, is another control strategy.
Hydrogen peroxide (H202)
Clear liquid with powerful oxidising activity. Sometimes used to treat skin parasites. Potentially harmful to fish, so use with caution and never overdose.
Can also be used in emergency to temporarily increase oxygen levels in aquariums suffering from low dissolved oxygen. Add 0.1-0.25ml of 3% hydrogen peroxide solution per litre of water for this.
Abnormal condition characterised by excess of blood in a part of the body. Hyperaemia is particularly noticeable on the fins of affected fish where it manifests as enlarged blood vessels resembling thin red streaks. It can also appear as patches of red-brown on the fins.
One possible cause is stress, perhaps due to deteriorating water conditions or overcrowding. In such cases, an improvement in environmental conditions may lead to hyperaemia clearing by itself.
Another cause is blood poisoning (septicaemia), often due to a serious bacterial infection which will require antibiotic treatment.
Abnormal increase in the number of cells within a tissue or organ. Hyperplasia often occurs in response to an irritation or infection: for example, the fish’s gills may undergo hyperplasia as a result of damage caused by parasites such as gill flukes.
Reduced oxygen level within the tissues. Affected fish may show signs of breathing problems, such as gasping and/or fast gill beats.
Hypoxia can be the result of a gill or blood problem: for example, gill damage caused by exposure to high ammonia levels, gill parasites or nitrite poisoning of the blood.
In some cases it is the result of insufficient oxygen in the water — environmental hypoxia, perhaps due to overcrowding or inadequate aeration. Hypoxia is potentially fatal and can cause sudden mass mortalities among fish. Methods for control and treatment depend on the underlying cause.
Genus of protozoan parasites, formerly known as Costia. The important species is Ichthyobodo necator. These single-celled parasites are ten microns in size (one equals one-thousandth of a millimetre) and affect the skin and gills of fish, and particularly target stressed individuals.
They are more commonly encountered in pond fish.
Affected fish produce excess mucus, manifesting as areas of whitish, hazy skin and there may be red areas on the skin and fins, and pale gills. The fish may also develop breathing problems and exhibit repeated body rubbing ('flashing').
When viewed under a high-powered microscope, Ichthyobodo appears kidney-shaped with two whip-like filaments known as flagellae. Treat the whole pond with a proprietary ecto-parasite remedy.
Genus name for the whitespot parasite and currently there’s only one species, Ichthyophthirius multifiliis, which affects freshwater fishes. These parasites appear as small white spots beneath the outer skin and other body surfaces of the fish — hence the common name whitespot.
Condition in which the fish’s immune system is weakened or impaired, making it less able to fight off infections.
There are many causes. In pond fish, such as Koi and goldfish, seasonally low water temperatures slow down the fish’s immune system. This explains why over-wintering pond fish are more prone to opportunistic infections such as fungus and carp pox virus.
Fish stressed, perhaps due to overcrowding or poor water conditions, can also become immuno-suppressed. This is because stressed fish produce elevated levels of certain hormones such as cortisol which has a direct inhibitory effect on the immune system. Old age, poor nutrition and certain medications (for example, the antibiotic oxytetracycline) can also suppress immunity.
Condition in which the fish is unable to produce viable eggs or sperm (milt). Infertility can have many causes. There may be natural reasons; the fish can be sexually immature, is too young to breed, or it may have an internal tumour or disease that has damaged the reproductive organs.
Poor nutrition and genetic defects have also been linked to cases of infertility. Some cultured fish are intentionally rendered infertile (sterile) to prevent spawning-related aggression or to increase growth performance — as in the case of some food-fish species. The underlying cause of infertility is often difficult to determine.
Iodine-based disinfectants. Effective against bacteria, viruses and fungi. Iodophors are used in some commercial aquaculture facilities to disinfect equipment — and fish eggs — but should never be exposed to live fish as these chemicals are highly toxic.
Antibiotic. Fairly stable in water so can be administered as a long-term bath treatment. Can also be given orally with the food. Use with caution as kanamycin may be toxic to some fish species. Seek professional advice if in doubt.
Genus of tapeworms. One species, Khawia sinensis, (originating from Asia) is sometimes found in the intestines of common carp and Koi in the UK. The tapeworm’s larval stage is carried by aquatic annelid worms, such as Tubifex. Khawia infestations are treatable with special drugs known as anthelmintics.
Tapeworms will be described in their own A-Z entry.
A dormant or ‘hidden’ infection. Fish harbouring a latent infection may appear perfectly normal and healthy, hence the infection often going undetected. Several types of virus, including the carp pox virus, may remain latent in their fish host for many months, possibly years. Typically, only when the fish becomes stressed and/or its immunity is lowered does the infection reawaken, causing disease symptoms to manifest.
Genus of parasitic crustaceans, commonly known as anchor worms which parasitise the skin and gills of fish.
Lernaea are more commonly found on pond fish, but occasionally occur on aquarium fish, especially wild caught specimens.
Only the females are parasitic, reaching 5-10mm/0.4” in length and resembling elongated strands attached to the fish’s skin. Each female produces a pair of egg sacs that give her a spindly Y-shaped appearance.
In their juvenile stages lernaea attach to the fish’s gills. Parasite damage to the skin renders the fish prone to bacterial infections and gill damage may cause respiratory problems.
Adult lernaea can be carefully removed using tweezers, but special anti-crustacean chemicals may be needed to completely eliminate anchor worms the pond.
Abnormal erection of the fish’s scales. This typically accompanies the bloating condition known as dropsy.
State of drowsiness or lack of energy. This is often caused by stress, disease, or adverse water conditions, so should be investigated without delay. Exposure to low water temperatures (as experienced, as an example, by over-wintering pond fish) can also cause a lethargic or torpid state. Bear in mind that many fish become lethargic when 'sleeping' — and this is normal!
Drug for treating gut-dwelling nematode worms, such as Capillaria worms that affect Discus, Angelfish and other cichlids. Available as Levamisole hydrochloride which can be given orally — incorporated with food — or added to the water at 1-2 mg/l as a 24-hour bath.
Abnormal curvature of the fish’s backbone which becomes kinked in the vertical plane. Typically, lordosis develops slowly and there are many causes, including genetic or developmental defects.
In some cases, a chronic bacterial infection, such as caused by mycobacteria, may be responsible. Various dietary deficiencies, including a lack of vitamin C (ascorbic acid), may lead to this condition.
Backbone deformities can also occur in old age.
Where lordosis occurs suddenly (within 24 hours) then a physical injury to the backbone is the most likely cause.
There is no known cure for this condition.
A relatively harmless viral disease that affects certain freshwater and marine fish. It manifests as white to pale pink wart-like growths on the skin and/or fins.
There can be single or several growths that sometimes develop into cauliflower-like clusters.
Affected fish typically remain otherwise healthy and do not body-rub — in contrast to fish suffering from whitespot or other irritating skin parasites. Often, only a single fish is affected.
Lymphocystis affects the more evolutionary advanced groups of fish such as cichlids, anabantoids (Gouramis and relatives) and Glassfishes. It does not affect catfishes, barbs or tetras.
There’s no chemical treatment, but recuperate affected fish under optimal conditions. This will help the fish’s immune system to overpower the virus, causing the growths to eventually disappear.
The disease generally attacks fish already stressed or diseased, so investigate why they became susceptible in the first place.
Why do our fish sometimes die for no apparent reason? There can be many causes, explains Nathan Hill.
To try to catalogue every possible reason for an aquarium wipe-out is a colossal and unrealistic task, but, when I was a store manager in the trade, I saw more customers who had 'inexplicable' losses than I care to remember.
Having investigated tank crashes through a variety of reasons, I’m confident that addressing a few potential problem areas could reduce outbreaks of this phenomenon.
What are the factors? Some crashes are understood, like the alarmingly common 'new tank syndrome' where over-enthusiastic newcomers fail to appreciate the importance of the nitrogen cycle. Here, rapidly-accumulating wastes build to a point before ravaging the aquaria with deadly nitrogenous compounds
But what about 'mystery' crashes? What could account for sudden losses in a tank running successfully for many years, a tank regularly maintained with water quality frequently checked? Assuming absolute basics have been covered, that the heater and equipment are all satisfactory, assuming that ammonia and nitrite are nil (or negligible), there’s surely no reason for fish to just die?
Old tank syndrome
Many problems were down to what I call 'old tank syndrome' although this is as much 'old test kit syndrome' as well.
Old tank syndrome is characterised by a chronic problem suddenly becoming an acute problem which could be avoided with proper testing.
Most of us realise the importance of regular water changes. They help to reduce nitrate levels, as well as phosphates and other dissolved organics, and they help re-buffer essential minerals that deplete daily. Most of us will use a test kit to ascertain the frequency with which we should be doing these changes.
So how much faith do we put in them? Kits, especially off-the-shelf liquid reagent varieties, have a finite life span. The moment you open the bottle there’s a limited time before the contents start to oxidise, making them inaccurate. And what use is a stale nitrate test kit?
How many people this week alone gave themselves a pat on the back on observing a marvellous reading, 5-10ppm perhaps, when in reality that figure could be closer to 100ppm.
How can this cause a wipe-out? Apart from accumulating nitrates, we should also think about the build-up of acids within the tank.
One of the many by-products of nitrification is the release of hydrogen ions into the water by our 'good' bacteria.
These ions are a key player in making water acidic. Combine this build-up of acid with gradual erosion of buffering minerals not adequately replaced through lack of water changes, and the tank slides towards disaster, losing ever more stability until reaching a tipping point.
The pH crashes, livestock — already weakened by chronic exposure to nitrate — are also suddenly subject to severe acidosis. Without immediate action, death becomes inevitable.
Acute acidosis is easy to spot as the fish quite literally try to get out of the tank. They jump, dart, race from end to end, and die.
But this is only one eventuality of a useless test kit. For others, the tank may start to harbour anaerobic patches (areas that lack oxygen through combinations of excessive nutrients and poor water flow) and these may give rise to undesirable bacteria, facultative anaerobes which convert nitrate back into deadly nitrite, or give rise to hydrogen sulphide.
This is a nasty chemical and is detectable through a rotten egg smell (being responsible for much of the odour associated with flatulence), as well as leaving black staining on any areas the anaerobic bacteria grow. It’s an effective poison, destroying the ability for cells to respire and causing fish to suffocate internally.
Often, bubbles coming from the substrate will be little more than nitrogen, but don’t ever become complacent. And, if you start to see black staining on the underside of decor or substrate, sort out your husbandry.
Older tanks may inadvertently stress new additions, assuming these arrivals have come from a clean and healthy environment. New fish in a tank are often blamed for the introduction of diseases, but how many of these situations could have been avoided if the newcomers had not been subject to 'nitrate shock'?
Combine this with 'established' fish with immune systems suppressed by long periods of chronic nitrate exposure, and such situations are asking for trouble
Avoid these types of crash by not putting too much faith in one old, possibly stale, testing kit. Replace liquid kits periodically and, if a result looks too good to be true, it probably is.
Tapwater is not the best medium for fish, at least not in its most raw forms. Agreed, it’s packed with chlorine, but If it wasn’t we’d all be running around with cholera.
Nowadays, almost all proprietary dechlorinators tackle both chlorine and chloramine.
Be careful if trying to use a product that only deals with chlorine, as against chloramine it will be counterproductive, releasing toxic ammonia into the water. That’s assuming it even touches the chloramine. If it doesn’t you have a problem.
Chloramine poisoning is similar to carbon monoxide poisoning in humans. It destroys the ability of the blood to carry oxygen and fish struggle if they can’t breathe.
When dechlorinating, give the product time to take effect. Adding dechlorinator after the water has been put in is useless. Pre-mix it in a bucket and give it a good few minutes to work.
Water companies are regulated as to what they can and cannot put into our supplies, and will usually notify us of any work being undertaken with domestic supplies.
In the long run, watch out for the addition of fluoride to tapwater. This is already raising concerns in America where it is now accepted that levels of 1.5ppm can prove lethal to salmon. Worryingly, optimal levels for fluoride use are between 0.7 and 1.2ppm — very close to that danger mark.
Beware other uses!
I’m amazed at how many people use their water changing equipment for other chores — such as washing the car or cleaning windows. Cleaning products are riddled with surfactants like sodium laureth sulfate which is lethal to fish.
Just look at any water course into which a soap has been discharged. They are there because they adore attaching themselves to fat and oil — great for dirty dishes, but not living organisms. The amount of soap required to kill a fish is painfully small and can leave no trace in the tank.
Many use equipment specifically for the aquarium— and nothing else. But where does it live? You’ve done your change, poured the water down the bathroom sink, sat the bucket on the floor and gone for a cuppa. In the meantime the kids have jumped in the shower, shampoo flying everywhere, including into your bucket!
When you put it back under the tank two hours later, the suds are just a residue, sat patiently on the side…
This scenario may sound far-fetched, but I’ve seen it all too often. Always thoroughly rinse any tank equipment before and after use. And don’t store it next to your household cleaning products. Things splash and, when they do, you’ll only find out to your cost.
It goes without saying that you never wash anything that goes into the tank with soapy water, including your hands. Residue will sit with you for hours after you’ve done the washing up, so rinse those things before you plunge them in to reattach that pesky algae magnet.
Be wary of anything new in the tank, too. I can think of many cheap ornaments smothered in highly toxic lead paint. Not that these are specifically destined for aquaria, but you can bet that if there’s a quick buck to be made from their merchandising, they will find their way into tanks.
Inappropriate types of wood leach toxic resins, porous rocks are stored next to bleach in the back of a fish shop — all dying to crash your hobby.
Always avoid iron. That old anchor may look great, but it’s wreaking havoc as the ferric iron (rust) is happily oxidising fish tissues, tearing gills apart and generally giving everything anaemia.
Smells of danger
Certain advertisements make me shout obscenities, especially when they advocate stupidity. Whenever I see a commercial on TV with yet another air freshener on top of an aquarium, I cringe.
I estimate that contamination from extraneous (outside the aquarium) sources accounts for over half of all tank crashes in this country.
Chemicals, such as those found in some air fresheners, are lethal. Crank the dosage up and they’d kill us, too.
Look at the ingredients of an air freshening fragrance and you’ll see all manner of innocuous sounding chemicals.
Examine them more closely and you might be tempted to go smelly for the rest of your days…
Take just two from a well known brand of scent. One is linalool, a lovely smelling chemical, spicy and floral, not only found in air freshening products but also soaps, shampoos, lotions and so on. It’s also used by pest controllers to kill fleas and cockroaches.
Ever heard of coumarin? It’s a chemical that gives off a pleasant hay smell and is used in many fragrancing products. It can also be used as a highly potent rodenticide, causing internal haemorrhaging.
Too many aquarists are unaware of these hazards sitting inches from their tanks although, in fairness, these products often have a warning about toxicity toward fish in microscopic print somewhere on the package.
Airborne chemicals don’t stop with air fresheners. Nicotine from tobacco smoke is lethal to fish and incredibly hard to detect.
The lethal level for a mouse is a mere 3mg per kilo body weight, humans are far lower (as low as 0.5mg), and although fish are quite high by comparison (over 68mg for a goldfish) nicotine uptake through the gills behaves a little differently than through the lungs — not to mention the bioaccumulative nature of the tar.
To put that into perspective, the nicotine from one 'normal' strength cigarette could kill about five or six large mice. A large mouse weighs in at about sixty grams — and I’ll bet a guppy is lighter!
Insecticides are a guaranteed killer. One of the most commonly used is permethrin, which can be lethal to some fish at doses as low as 0.0018mg per litre. That’s tiny and it can be accumulative, having a half life of two and a half days in water and creating time to build up to lethal levels inside a fish.
If it emits fumes or vapour, it will be dangerous to fish. And I’ve not even touched on paints, polish, joss sticks, glues, solvents, wood preservatives and the hundreds of other deadly chemicals in our homes.
Poisoning of this nature can be easy to spot. Expect fish to be incoherent, if even still alive, lying on the bottom and shimmying. A poisoned fish will often fail to react if you try to touch it —not that you should — and, strangely, a poisoned fish will often exhibit intense coloration, far brighter than usual.
Often symptoms can become apparent over a very short period, especially if the tank is using an air pump to increase oxygenation or water movement. Water is incredibly good at trapping suspended particles from the air.
The remedy depends on the type; chronic or acute. For acute poisoning, the fish need to be transferred immediately to a toxin-free environment. For chronic poisoning, all you can do is remove the cause and perform frequent, large water changes in the hope that fish have the strength to flush themselves through.
Prevention is better than cure. If it creates a scent, keep it away from the fish. If it can transport itself through the air, keep it away from the fish!
How many of us bring water up to the correct temperature when doing a water change? I’d like to think most of us do, as, although rare in causing a wholesale crash, dissolved gases can still play havoc in a newly changed tank.
We’ve all taken a glass of water to bed, freshly drawn from the tap and nice and cold. In the morning it will be full of small bubbles and taste differently. This is because, as water warms, it loses its ability to hold on to certain dissolved gases, chiefly nitrogen.
The same will happen if we pour cold, dissolved gas-rich water into our aquarium. It will warm and the gases will form tiny bubbles as they come out of saturation. If your fish have taken big breaths of this cold water the gas will form bubbles inside them, in a way not unlike nitrogen narcosis (the bends) in humans.
Before racing for that hot water tap, however, think about where that water’s coming from.
Many houses have huge copper tanks to store hot water, not to mention all the copper piping feeding from them— and you don’t want this metal building up in your tank, especially if keeping marines! If heating water before use try a small amount of water heated in a kettle, but be extremely careful how much you use. Boiling water can play havoc with the temporary hardness content.
Buy food wisely
It may seem economic sense to buy a huge pot of dried fish food — and some people can make a good-sized tub last over a year.
But this is not a sensible move. Not only will food lose its vitamin content, but ongoing moist exposure, such as wet fingers going back for a second pinch, may lead to aflatoxins which are by-products of mould growths and poisonous to fish.
Although unlikely to cause an overnight crash, aflatoxins will contribute as a chronic stress factor, weakening immune systems and making fish more susceptible to other influences.
How about plants? Retailers tend not to stack a range of plants safe for consumption. Certainly two plants I’ve started to see more and more of recently are Caltha palustrus and Lobelia cardinalis and both are toxic. Are you sure you want your Silver dollars munching on them?
Many harmless-looking foodstuffs may be harmful to fish.
I remember having many years ago some young Metynnis who just loved to eat seeds from my apple cores, but only later did I discover that these are riddled with amygdalin, a cyanide-producing compound that can even prove fatal to humans in high enough doses
Danger close at hand
So, danger lies around every corner of your home, at the bottom of every bucket, and in every pleasant-smelling scent inside your four walls. The tragedy is that most events that cause a wipe-out will never be discovered — the cause so innocent as to be totally unremembered.
So before shouting at your local dealer and accusing him of selling you the fish that wiped out your tank, think first. Was there anything harmful that could have got in to do the damage?
Is there something sitting harmlessly all this time, waiting to savage your livestock? If there is, and you find it, let others know. It would be a massive undertaking to try to list everything that could cause tank crashes — but in doing so we could all make the hobby a far more rewarding place.