Movie aliens and monsters have nothing on the octopus when it comes to weirdness. And, so long as you can meet their needs, these animals make intelligent, interactive pets.
WORDS: DAVE WOLFENDEN
Frankly, you’d be hard pressed to make anything up as bizarre as an octopus. They lack a skeleton, but are extremely strong; they suck their liquidised prey through a hole in the middle of their brain; their eight arms are covered in independently-controlled suckers;
they have three hearts, blue blood and can change the colour and texture of their skin.
Octopuses are molluscs, belonging to a group known as the cephalopods (meaning ‘head foot’), making them relatives of squids and cuttlefish. They possess a muscular ‘cloak’ known as a mantle which covers the internal organs, and have a system of jet propulsion thanks to a structure known as the siphon. Rapidly forcing water through the siphon allows for rapid movement. As the shell has been reduced either entirely, or at least is now reduced to vestigial fragments in the mantle, they’re quite vulnerable, so octopuses have developed this ability to evade predators as a defence mechanism. It may be assisted with a puff of ink (which can act as a ‘smoke screen’, or perhaps act as a diversionary tactic to distract a pursuing predator).
To avoid being detected in the first place, these amazing animals adopt cryptic behaviours, and are able to change the colour of their skin via pigment-filled sacs called chromatophores, as well as its texture, thanks to structures known as papillae located across the body.
Octopuses are intelligent, with a natural curiosity to explore any part inside or outside of their aquarium; as a result, they’re interactive, and can assume full pet status.
Octopuses in the aquarium
It is possible to successfully maintain octopuses at home, but they require some key aspects of husbandry if they are to thrive.
Size: Octopuses can vary wildly in size, so it’s difficult to give recommendations as far as tank volumes go, but I’d suggest that the animal needs to have sufficient room to explore, and you’ll need to really judge each specimen on its own merits. If the length of the aquarium is around four times the arm span of the animal, this is a reasonable size.
Filtration and life support: Octopuses are messy feeders with a big appetite, so they generate a lot of solid waste. Therefore, mechanical filtration needs to be able to cope adequately, and the media should be cleaned or replaced frequently. An octopus system will have a relatively high bioload, thanks to the animal’s food, and the ammonia generated by the octopus itself, so efficient biological filtration is essential. Octopuses require optimal oxygen saturation, so ensure adequate turnover. This is important thanks to the relatively inefficient respiratory pigment haemocyanin. They’re not too fussy about nitrate, but aim for zero ammonia and nitrite.
A skimmer will help with ensuring oxygen saturation, as well as pulling out as much waste-laden skimmate as possible. Ozone isn’t tolerated well by cephalopods, so don’t use it.
Water: The quality of the salt water you provide is crucial for keeping octopuses, and they don’t do well in certain budget ‘fish-only’ brands of salt. Use RO water for make-up, and opt for a good, reef-quality salt to be on the safe side. Copper and other metals are a big problem for octopuses, so this is very important to observe. And employ chemical filtration courtesy of activated carbon at all times.
Aquascaping: Most of the octopus species available in the trade are from heterogeneous rocky environments, so replicating this habitat is essential if the animal is to feel secure, exhibit its natural behaviour, and display well. Provide lots of nooks and crannies for the octopus to explore.
Lighting: Your octoquarium should have sufficient lighting to see the animal, of course, but many species won’t tolerate excessively bright illumination. In fact, some octopuses are nocturnal, so you won’t see these until ‘lights out’ generally, although they can adapt to a certain extent.
Enrichment is very important for the long-term health and welfare of octopuses. There are various things which you can do to provide stimulation for the animal. Try randomising feed times, making your octopus work for its food, and simply interacting with it — you don’t have to overdo things, but get creative.
Octo-proof your set-up
As escape artists, octopus would make Houdini blush. As they have no bones or shells to get in the way, they can squeeze their muscular, flexible bodies through the tiniest of holes — it’s as if they can turn themselves into liquid and pour through the gap. And given a chance, they will. Exploration is irresistible to them. Leave them in an open-topped tank, and you’re as good as asking them to leave.
Therefore, a tight-fitting lid is an absolute must. This could be made of glass, or it may incorporate mesh (obviously of the plastic, non-toxic variety), but crucially it must have small enough gaps to prevent escape. This obviously varies according to species or size of individual, but in some cases even a few mm is enough for them to get through. Bear in mind, too, that they’re strong, so any lid needs to be firmly fixed into place to prevent it from being pushed up.
Some public aquariums use wide bands of Astroturf to line the top of their octopus holding tanks to prevent escape — the octopus can’t grip the material properly. However, it’s not really a practical solution for the home system.
Octopuses are extremely curious animals, and it’s vital to ensure that any equipment which could harm them, such as heaters and filter or pump inlets, are well out of reach. Some ingenuity might be necessary to octo-proof any overflows and weirs.
Octopuses are voracious predators, with feeding facilitated by a parrot-like beak and a rasp-like radula, used to macerate their prey; they also possess venom glands used to immobilise the victim. They need to be fed regularly (daily or every other day); provide thawed crustaceans (crabs or prawns) or appropriately-sized fish. Octopuses adapt well to accepting frozen food, and this is preferable. However, they may need to have it presented to them on a feeding stick to get them used to it.
Octopuses generally don’t do well with conspecifics, thanks to cannibalistic and aggressive tendencies, and only a few species can be kept in groups. All the commonly-available species in the hobby should be kept singly. As for housing them with fish — it’s a no-no. Larger species may try and eat the octopus, while the octopus will make short work of smaller species. Many corals and anemones will sting the cephalopod’s sensitive skin, and the octopus will predate upon mobile inverts and clean-up crew. On balance, a dedicated species system is the way to go.
Live fast, die young
Octopuses don’t tend to have long lifespans, which can be an issue. Some small tropical species may live for no longer than six months after hatching, and individuals may be several months old when they make their way into the trade. For a medium-sized species such as the Common octopus, Octopus vulgaris, two years is good going, and with the Giant pacific octopus, Enteroctopus dofleini, which lives in very cold water, you’re looking at just five
years — tops.
A male octopus may suddenly die without apparent warning, but a female will naturally undergo a process known as senescence. She lays eggs (which may be either fertile or infertile depending on whether she has mated), and then spends the rest of her short life tending to them. She’ll refuse food and slowly lose condition, possibly over several weeks.
Senescence can be a distressing phenomenon to watch, but it’s a fact of octopus life — you have been warned.
We don’t know an awful lot about octopus disease. Occasionally, parasites may be a problem, as can bacterial infections of the skin — but these should be left to a specialist vet to diagnose and treat if necessary.
Most health issues are primarily due to environmental factors: for example, ammonia spikes or metal pollution; or through boredom. Therefore, maintaining ideal water quality and a stimulating environment should reduce any potential health problems.
Beautiful — but deadly!
There is a genus of octopuses you’ll want to avoid. Get bitten by one of these, and you’re in for a world of hurt — and they’ve been responsible for deaths. I’m referring to the blue-ringed octopuses (genus Hapalochlaena), of which there are several species.
Blue rings tend to be small (with a span of only 10cm/4in maximum) and beautifully coloured, but they harbour bacteria in their salivary glands which synthesise tetrodotoxin (TTX). TTX is one of the most potent neurotoxins known, and according to survivors, the consequences of a bite sound terrifying, including paralysis.
Amazingly, these animals are imported; they’re not actually illegal to keep under DWA (Dangerous Wild Animals) licensing, but no responsible retailer will sell you one. I know of one dealer who was more than a little concerned when several blue rings were added into a shipment by the collector as a sort of ‘freebie’. Luckily, the dealer donated the animals to public aquariums able to house them.
4 octopus for the aquarium
Octopus offered for sale will often simply be labelled ‘Octopus sp.’ due to the challenges of conclusively identifying them. However, a few crop up frequently which can fairly easily be given an ID. For others, you’ll need a good book such as Mark Norman’s Cephalopods: a World Guide.
Scientific name: Octopus vulgaris (Oct-oh-puss vul-ga-riss).
Origin: Worldwide, across temperate and tropical seas.
Size: At least 60cm/24in span, and perhaps up to 1m/40in.
The Common octopus is frequently offered for sale in the hobby. The situation is a little confusing, as several species from a ‘complex’ are actually sold under these scientific and common names.
Scientific name: Octopus horridus (Oct-oh-puss ho-rid-uss).
The Octopus horridus complex comprises several Indo-Pacific species, and you’ll often encounter these. They tend to have long arms and adopt an extremely cryptic way of life. However, the escape abilities of these octopuses are second to none.
Scientific name: Octopus bimaculoides (Oct-oh-puss bi-mack-you-loy-deez).
Origin: Pacific Ocean.
Size: Up to 50cm/20in span.
Distinguished by the two eye-spot markings, this species is closely related to the larger O. bimaculatus.
Scientific name: Octopus cyanea (Oct-oh-puss sigh-an-ay-ar).
Size: Reaches nearly 1m/40in in span.
Due to its eventual size, this species will require a very large aquarium.
Dave Wolfenden explains how slug and snail molluscs can make your reef tank a cleaner, happier place.
Gastropods, which includes slugs and snails, are a diverse group. They comprise some 40,000 species whose habits range from grazing herbivores to out-and-out predators.
Many can be usefully employed in the aquarium for their janitorial capabilities, primarily for their ability to graze away nuisance algae.
Correct identification of any can be tricky, however, and it’s important to determine the habits and size of any purchase to prevent nasty surprises.
This genus name is inspired by the shells’ resemblance to a turban. Many snails are sold generically as ‘turbo snails’, although the real deal refers to only a few specific gastropods, identifiable by their rounded shell shape and their operculum — a flap used to close off the aperture.
Overstocking is a common mistake when adding these to the aquarium. One per 50 l/11 gal is usually a sufficient ratio, as algal growth needs to be able to sustain any Turbo population.
Tectus and Trochus
These are also sold as the 'giant turbo', due to their resemblance, and larger ultimate size — some growing to more than 8cm/3.1” across. They usually have a smooth shell too.
Being large, overstocking is common as a surprising amount of algal growth is needed to sustain them. Aim for no more than one snail per 100 l/22 gal.
Frequently offered is the Banded trochus (Trochus histrio) from the Indo-Pacific, which is a good value and hardy grazer.
Snails of the Cerithium genus are often available as part of the reef aquarium’s janitorial crew and these cone-shaped molluscs are always an excellent choice because of their excellent grazing and scavenging abilities.
These hardy snails are also frequently sold as 'turbos' and handy on account of their small size, making them ideal for nano systems. Consider one snail per 25 l/5.5 gal. Astraea tecta is worth considering, if only because of its attractive pyramid-shaped shell.
The conches of the Strombidae family can greatly enhance the captive reef and some species can make short work of algae as well as consuming detritus in hard-to-reach places.
The Caribbean queen conch (Strombus gigas) grows to 30cm/12”, making it unsuitable for home aquaria. Instead, opt for one of the smaller sand-sifting conches (Strombus spp). These plough through the substrate, consuming detritus and filamentous algae, so provide a suitable sand bed.
These can make excellent grazers, although there are exceptions and research and positive species ID is essential. They’re characterised by highly polished shells, at least partially covered by the mollusc’s mantle during movement.
The most commonly kept species in the aquarium are the Money cowrie (Cypraea moneta) — pictured above — and the Ring cowrie (C. [Monetaria] annulus). Both of these Indo-Pacific creatures are small and make great janitors.
The Tiger cowrie (C. tigris) can be iffy. Characterised by its mottled brown and beige shell, this Indo-Pacific species grows to some 10cm/4”, depending on where it was collected. These can dislodge rockwork as they bumble around and, while useful scavengers, may also predate on sessile invertebrates. Anemones, soft corals and sponges can all be potential victims.
If it’s weird you want, how about one that looks like lettuce?
The sea hare is a completely different nudibranch. It is so called because of the ‘bunny ear’ appendages known as rhinophores and used for chemical detection.
Sea hares may use extensions of the mantle to swim, which is quite a sight.
Some species are challenging, due to specialised feeding requirements, but a few may be attempted by the dedicated.
For example, the Frilly sea hare (Elysia crispata, formerly known as Tridachia crispata) at up to 8cm/3.1” and from the Caribbean is a strict herbivore. It requires plenty of algae and mature live rock, but a specimen can be sustained in a reef aquarium.
This species has highly variable coloration, but it’s easy to see why adults are given the common name of Lettuce sea slug, thanks to the bizarre folded lobes adorning the mollusc’s body.
Several imported gastropods shouldn’t be contemplated by responsible marine aquarists. These include:
Even potentially deadly, they are sometimes seen in the trade and are not restricted under the UK’s Dangerous Wild Animal legislation.
Members of the Conus genus predate other animals, including fish and other molluscs. They may be inactive during the day, burying themselves in the substrate. However, at night, they emerge to stalk their prey.
With a touch as deft as a ninja warrior, they can ambush sleeping fish and other hapless victims, spearing them with a modified disposable radula linked to a poison glad. The poisons are known as conotoxins and among the most potent neurotoxins known to science.
You can recognise most members of the genus, thanks to their distinctive shell morphology, as it’s easy to see why they’re called cone shells.
The Geography cone (C. geographus) — pictured above — is from the Indo-West Pacific and grows to 10cm/4”, while the Literary cone (C. litteratus), up to 13cm/5.1” and from the Indo-Pacific, has distinctive brown spots on its yellow shell. The Textile cone (C. textile) growing to 10cm/4”, is also an Indo-Pacific species and has a beautiful shell, making it highly prized. Just don’t think about keeping one, as all are also venomous predators!
True sea slugs or nudibranchs (meaning ‘naked gills’) comprise some of the ocean’s most psychedelic animals and their stunning coloration betrays their toxicity to would-be predators.
In fact, their distasteful nature is often due to their ability to sequester (store) the stinging cells (cnidocytes) from their prey, such as corals and hydroids. The undischarged cells are known as kleptocnidae (‘stolen stings’) and can be deployed against any potential predator.
The aposematic (warning) coloration of nudibranchs seems universally recognised, as they are given a wide berth. Many species are tiny, but some range up to nearly 0.5m/1.6’ long.
Occasionally seen and quite expensive is the Spanish dancer (Hexabrachus sanguineus). This 40cm/16” creature has a wide distribution from the tropical Atlantic to the Indo-Pacific and there’s great coloration diversity among individuals.
Its common name is inspired by its habit of ‘dancing’ flamenco-style when swimming, courtesy of flapping actions of its mantle.
These are difficult to maintain, due to their diet of sponges — and this species is among the least fussy of nudibranchs. Incidentally, this plays host on the reef to the Emperor shrimp (Periclimines imperator), which hitches a ride as well as feeding on its mucus secretions.
While their beauty makes them highly desirable, feeding habits make nudibranchs a poor choice and responsible aquarists should avoid them.
Many species are obligate feeders of one particular prey species of coral or hydroid — in other words, they can only survive on that species and will starve if their natural diet is not provided.
Species ID is complicated and matching a nudibranch to its natural diet, plus providing adequate quantities of that diet, is beyond the realms of most.
Murexes (Murex spp.) are occasionally picked up by some unwitting reefkeepers who live to quickly regret their decision when this predatory snail has finished off other molluscs in the tank as well as tubeworms.
To be fair, it’s easy to see why murexes are so appealing, thanks to their bizarre shell shapes adorned with prominent spikes.
However, these fascinating and expensive gastropods are not suitable for most reef systems, although they can be successfully kept in a FOWLR (Fish Only With Live Rock) aquarium system with a few fish.
Never use any copper remedies
Gastropods are extremely sensitive to copper, so never subject them to copper-based medication — and grazers need to be introduced to systems with sufficient algal growth to prevent starvation.
Supplementary feeding may be necessary in certain cases.
Gently does it
Gastropods, as with all molluscs, fare badly if subjected to rapid changes in temperature and/or water chemistry. For this reason, take extra care and plenty of time when acclimatising them and use the drip method to ensure fine control when altering water parameters after transport.
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Nothing seems to compare to the fearless Mantis shrimp. It has the brains and weaponry to make it the most special of agents, as Nathan Hill explains...
If humanity destroys itself tomorrow who takes over the world? Rats? Cockroaches? I’d hazard that the seas would become the domain of the Mantis shrimps.
Mantids are natural-born record breakers and perfect examples of niche adaptations thrown up through evolution. They have probably the best eyes in the world and an explosive, superhuman punch.
Despite the name, Mantis shrimps are not shrimps at all; there’s little 'prawny' about them, despite their shared crustacean origins. They look like a cross between the secret lovechild of a praying mantis — from where they derive the mantid part of their name — and a lobster, and the front of the former seems to have been grafted to the rear of the latter.
There are some 400 species of Mantis shrimp too, ranging from midgets of just a few centimetres to beasts longer than a man’s forearm,
There are two ways by which you’re likely to meet one in an aquarium; deliberate purchase, or accidental addition via live rock. Their survival skills are up there with Bear Grylls.
Unceremoniously uprooted with a piece of rock, packaged in a dry box, subject to changes of temperature, and exposed to horrendous water in a curing tank — mantids have frequently endured all of that without so much as a shrug.
Get one in your tank and it will start to make a dinner platter of the other inhabitants — but removing such a stowaway Mantis can be a challenge as they move fast to secrete themselves away in a cave at the first hint of danger.
The first sign of their presence may be some mutilated fish and inverts, so get searching for their rock of residence.
Given how many aquarists are mantid fans as projects in their own right, that might be all you need to do. Simply stick them and their rock in another tank and you’ll have a free, fascinating pet — plus it’s a perfect excuse to get another aquarium in the house!
Smash and grab
It’s impossible to talk of a Mantis shrimp without referring to its weapons of mass destruction, in the form of raptorial appendages — either being a spearer/grabber (pictured above with its long, hinged arms) or a smasher (pictured below, showing off one of his toughened, high speed hammers). These either lunge and spear prey or deliver a devastating hammer blow that stuns and physically shatters their opponents.
Size for size, smashers have the most powerful 'punch' of any creature. Although their clubs have the acceleration of a .22 rifle bullet, they don’t have the velocity, but this isn’t to undermine their power. The speed of a smasher’s club is around 20m/66’ a second, or 45mph, and this can result in prey receiving a right old belt of up to 1,500 Newtons.
These clubs even lower the pressure of the water ahead of them, causing it to vaporise and cavitate. In a moment this cavitation collapses, releasing a second burst of energy of up to another 590 Newtons against the prey. This creates not only heat and an audible sound but also a momentary explosion of light. When a Mantis strikes, its hapless victim literally sees stars!
The punch is driven by a muscle and lock mechanism inside the arm that causes huge amounts of energy to be retained. Once withdrawn, the whole arm is tensed and ready to shoot forward, much like a crossbow. All the Mantis need do is release the lock!
Just prior to moulting, a Mantis gets volatile, smashing everything in range. Yet for a short period over the moulting cycle it is helpless, and instead resorts to bluffing, waving its arms and showing two colourful patches directly connected to its strike power.
It’s thought that this behaviour fools rival mantids into thinking it’s still fighting fit.
Shields at dawn
The tail of a Mantis is surely an armoured work of art.
Impact resistant, the chemical structure of their telsons has long been analysed and military intelligence sources in particular want to know more about what makes them so tough.
When two smashers meet they may go tail on, exposing only this hardy part to their foe which will smash against it. In return the other smashes back. Such fights are often just ritualistic and may result in both shrimps retreating.
However, in the event of one clubber invading another’s cave or burrow, this tail is the first line of defence to block attempts at entry.
During their reproductive phases, mantids fluoresce to show their receptiveness. It’s easy to seek suitable partners when their bright patches are shining.
Eyes that see so much more
Mantis eyes are extraordinary. While humans have three colour receptors a Mantis shrimp can have up to 16 of them.
Having 11 or 12 of those receptors devoted to colours, they see the world in a far wider spectrum than we could ever hope to imagine, including way up into the infrared and down into the ultraviolet wavelengths.
There are also colour filters and even polarization receptors so, unlike any other animal, Mantis shrimp can see polarised light and the reasoning behind this may well be down to breeding or other means of communication.
The ability to display in polarising light means that mantids can potentially make contact with each other without the risk of revealing themselves to other predators.
This ability to communicate in colour could also be pretty essential for these shrimps when they begin to seek out a mate.
Though the two eyes appear on stalks, they are comprised of 10,000 individually processed ommatidia, so not only do they have independent vision at the top of each stalk but the very shape and curvature of each eye enables depth perception. They can therefore focus on several objects at once.
Mantids also have an acute sense of smell, combined with an ability to learn fast.
When a Mantis first meets an octopus, for example, a fight will ensue. After that it remembers what an octopus smells like and when it comes across a burrow with octopus aroma, it will instantly tense up, assume a battle stance and enter cautiously.
These creatures have no fear of the high toxic Blue Ring octopus, clubbing it until the venom sac ruptures and the danger of being poisoned passes as it dissipates into the water.
Whether they map their neighbourhoods visually or through smell isn’t fully understood, but we do know that when a Mantis sets up a home it learns its surroundings intimately and can find its way about with ease.
Can I keep them?
You’ll need to keep this shrimp solo and set up a tank specifically for it. Other moving inverts will be bludgeoned, fish minced and sessile inverts and corals knocked over.
This is a creature destined for a sandy, rocky tank, imitating its natural range.
The likeliest offering you’ll come across is the Peacock mantis (Odontodactylus scyllarus). These brightly coloured, highly intelligent pets are both long lived and reach a reasonable 18cm/7”, so although a huge tank is not essential it’s better to provide one if keeping a Mantis long term.
Given that some species live longer than 20 years, and typically Peacock keepers report seven to ten years, it’s an inhabitant you’ll be looking after for quite a while.
Provide a tank of around 120cm/4’ long, and offer a thick, sandy substrate as mantids are burrowers and will freak out in a bare tank. Add a few pieces of live rock and it will excavate a cave for itself in next to no time.
Keep lighting low and high-intensity LEDs or metal halides are not needed. Even a single T8 tube will provide all that’s necessary.
Feeding is a doddle but if done badly is dangerous, as can be the case with maintenance. It’s not for nothing that these creatures are nicknamed 'the thumb splitters'.
Never try to hand feed. Even tongs and tweezers can be knocked clean from your fingers, broken, or snatched and carried back to their lair. Mantis are fast and indiscriminate and can easily tear flesh and crack fingernails in two.
Peacocks have little fear of novel objects and when you change water, they will approach to investigate. Always know exactly where your Mantis is when you work on the tank — as it’ll know exactly where you are!
Aside that, their requirements are minimal. Feeding can involve any snails, shrimp, squid and pieces of fish, which they will take greedily. Don’t overfeed them and once every few days is adequate.
Run the Mantis tank as you would a FOWLR system, using a good skimmer — given their rich, meaty diet — and external or sump filtration.
Although they have no particular water needs, mantids won’t do well in poor water quality and can succumb in polluted conditions.
Tease them at your peril!
There are a few reports of large smashers breaking aquarium glass and it is a real, if low likelihood hazard.
They like to strike at anything, so if you happen to be on the other side of the glass, teasing them with a shiny key or food, don’t be too surprised if they dispose of the pane to get to it.
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Take away a piece of a mother coral and that son or daughter will grow and carry on the family line. Dave Wolfenden explains how easy it is to cut away or simply prune them.
Fragmenting corals is now a widely used technique for propagating specimens and the number of species which can be successfully 'fragged' just keeps on growing.
For many corals fragging is ridiculously simple. If you maintain the correct water quality and provide adequate lighting for your 'mother' colony, there’s no reason why you shouldn’t produce frags.
The process involves a variety of techniques, but they all exploit the remarkable regenerative and asexually reproductive powers of the parent colony. While the techniques may seem drastic, remember that ocean life is tough and corals have adapted to a harsh existence.
Many will naturally regenerate from broken portions of their branches, either through wave action or damage by other animals. Division also naturally occurs as a reproductive strategy.
Not only that, some corals and mushrooms practise pedal laceration in which fragments of the pedal disc break off to form a new animal.
This is a bit like your toes occasionally dropping off, only to grow into a complete replica of yourself…
Why do it?
There are several reasons, notably creating new colonies — yes, free corals! These can then be used to increase the population of your own aquarium, sold or given to
Some corals may simply need pruning. Under the right conditions many SPS will grow extremely quickly and thinning out the colony to prevent shading and stinging may be required. So you may need to frag as a matter of course.
Corals may also need fragging to prevent individual colonies and sometimes whole systems being infected with various ailments. For instance, RTN (Rapid Tissue Necrosis), which sometimes affects SPS corals, such as Acropora, is bad news.
However, affected specimens can be saved simply by cutting them above the advancing band of necrotic tissue, discarding the dead portion and remounting the cutting.
Select your tools
The tools needed for fragging are fundamentally very simple. You’ll need some way of dividing the parent colony and while some more delicate species can be divided simply by breaking branches with your bare hands, some basic implements will usually be necessary for aquarist safety and the coral health.
A very sharp knife is pretty much all you need for soft corals and mushrooms, and a scalpel would be ideal. Pliers or pincers work nicely for many species, but a saw will be necessary for some. An electric rotary saw, such as a Dremel, will make short work of stubborn corals.
However, a Dremel can produce a lot of heat, which may damage the coral’s tissues, so ensure adequate cooling with water when cutting.
For obvious reasons, always wash any tools in fresh water after use. Stainless steel tools will resist corrosion, but eventually rust may appear if they’re used frequently. I avoid lubricating fragging tools with oils as the delicate tissues of the fragged specimens may react poorly to them, but this means that post-use rinsing is mandatory.
After you’ve obtained your frag, you’ll need some way of attaching it to a substrate for growth and some can be pushed into natural or pre-drilled holes in the aquarium’s rockwork. They may also be glued in place with cyanoacrylate adhesive ('superglue').
It’s also possible to use epoxy putty and this can work well with many SPS.
Physically tying fragments in place is another strategy. Soft cable ties, for example, can sometimes be used to attach a frag and the fixing will be simply grown over by new tissue. Some frags needn’t even be fixed in position, simply requiring to be placed where they won’t get blown around.
If suitable places already exist in the aquarium, then great. Many fraggers construct simple shallow mesh-covered trays which allow light to penetrate and water to flow adequately enough for frags of LPS, such as Fungia species, to establish themselves.
Small Polyp Stony (or Small Polyp Scleractinian) corals are generally rapid growers, favouring the highest intensity light and requiring the most attention to water movement and quality.
Having said that, they are also often easy to propagate.
Acropora, for instance, can be fragged simply by cutting off a branch with a pair of pliers. Applying leverage downwards will help to cleanly snap off the branch, which can then be mounted into its new location.
Simply dry off the exposed portion of skeleton and apply a blob of cyanoacrylate gel before sticking in place — and don’t worry about leaving the frag or parent out of the water for a few minutes. The best results will come from branches with active growth.
Plating SPS such as Montipora require a different approach, although the steps for attaching frags after breaking them off is the same. Carefully break off one of the plates by moving it up and down, being careful not to destroy the aquarium’s rockwork.
Then simply cut the plate into small pieces, remembering which is the upper surface of each. Then attach the frag as before, using superglue.
The morphology of many LPS (Large Polyps Stony or Scleractinian corals), in contrast to SPS species which have adapted to absorb wave action, makes them less straightforward to frag.
Growth rates are generally lower than for SPS, but many are definitely worth attempting.
Caulastrea, a branching LPS, is a good starting coral. Simply break off polyps at the base of the branch, preferably with pliers or pincers and epoxy putty can be used to attach the frag.
Fungia (plate corals) require extreme measures, thanks to their flat, plate-like morphology.
Using a saw, the underside of the coral can be divided into sections 3cm/1.2” square or more. Once the saw has nearly gone through the whole skeleton, the job can be finished off with cutters.
The frags will need to be protected while they recover from this 'minor op' and a
shallow, mesh-covered tray would be ideal for this purpose.
Soft corals and mushrooms
Before getting busy with the blade, gently brush the parent coral’s polyps, encouraging them to contract for you. For the branching species such as many Sinularia, simply lop off branches as necessary.
Mushroom-shaped softies such as Sarcophyton may be fragged by cutting a small piece off the cap.
Attaching the frags is tricky with soft corals, because of their slimy nature.
Depending on the morphology of the species, employing shallow trays or attaching the frag with a plastic toothpick pushed through the base can work well.
For mushroom corals, cutting off the oral disc at the base will be the the first step. to take. Then cut the disc into wedges.
If placed in a shallow mesh-covered tray, the fragments will grow into a new animal within a matter of weeks.
Always glove up
Wear latex or vinyl gloves when fragging. They protect you from the slime the coral will produce, as well as protecting from the nematocysts (stinging cells) which will be activated and minimising the number which fire. They also help to protect the delicate coral tissue from possible infection.
Dips reduce infection risk
Many fraggers use dips when cutting. Many commercially-available ones are iodine-based — and iodine is a potent antiseptic. Using dips is good practice as it can help limit the chance of infection in the sensitive cut tissues.
Conservationist authority attacks the principle of captive fragging
Some coral reef conservationists don’t like hobbyists undertaking captive fragging.
The International Convention on Biological Diversity (CBD) aims to ensure that biological resources, such as corals, are kept within their place of origin for sustainable exploitation and feels that fragging hobbyists violate the aims of the convention.
A strong lobby says this removes the opportunity for people who could sustainably harvest and export the coral from its natural habitat to do so.
While many see exploitation of natural reefs for the trade solely as a bad thing, there’s a counter-argument that a high-value/low-impact sustainable trade could be a major influence in keeping reefs safe rather than employing other more destructive means of their exploitation.
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Hermit crabs can look incredibly bizarre and have bright coloration, fascinating behaviour and endearing personality. And there's a hermit for most marine systems â€” although you need to be careful when choosing which species. Dave Wolfenden explains...
Hermit crabs are not strictly crabs. They’re anomurans and differ from ‘true’ crabs in their specialised morphology. Due to having a soft abdomen, they are notorious for utilising mollusc shells, as well as pieces of coral skeleton and even pieces of litter such as bottle tops when the opportunity arises.
Most species exploit gastropod (snail) shells and, as a result, hermits exhibit a torsion, or twisting, of their abdomen, along with a 'handedness' in most species — with the left chela, or claw, being larger than the right.
Feeding habits and temperament varies tremendously. Some are tiny and make excellent cleaner crew in reef aquaria. Others may be big bruisers, capable of catching fish and wreaking havoc with anything but the largest tank mates.
Always provide spare shells for them to grow in to and the bonus is being able to watch the associated behaviours. The crab will meticulously inspect the interior of any potential new residence before — if all seems right — moving in smartish!
Meet the species
Several species are great cleaners, consuming nuisance algae and leftovers as well as turning over the top layer of the substrate.
Among the best for the smaller reef are the Blue-legged hermit (Clibanarius tricolor) which grows to 2cm/0.8” across and the Red-legged hermit (Paguristes cadenati) which reaches to 3cm/1.2” and both originate from the Caribbean.
These diminutive but highly active hermits are also very attractive, readily showing off their brightly coloured legs.
However, there are provisos. Never crowd too many into the aquarium and aim for just one hermit per 50 l/11 gal of water to avoid over-competition and aggression between individuals.
Another issue with overstocking is that they will tend to become more destructive as population density increases — presumably as food supply becomes limited.
While these two species will happily scavenge under light stocking conditions, as well as consuming hair algae and even cyanobacterial films, they will resort to consuming both sessile and some mobile invertebrates if hungry. At particular risk are molluscs, such as topshells and Turbo snails.
The Blue-knuckled hermit (Calcinus elegans) — pictured above by Haplochromis, Creative Commons — is often used as a reef cleaner and although it can be a grazer of problem algae this species can be hit-or-miss. From the Pacific, this hermit grows to 5cm/2” across and is identified by electric blue stripes on its dark legs.
It will often damage delicate sessile invertebrates by clumsily wandering over them and it will become aggressive if overcrowded with conspecifics. It may also consume grazing gastropods, so supplement the feed regularly to minimise any likelihood.
The Dwarf zebra hermit (C. laevimanus) owes its name to the black and white stripes adorning its legs. Growing to around 4cm/1.6”, this Pacific species also sports blue eyes and orange antennae, so is quite a looker. This species is a good grazer as well as being a useful scavenger.
The fantastically, if inexplicably, named Halloween hermit (Trizopagurus strigatus) — pictured by Haplochromis, Creative Commons — from the Hawaiian Islands and Indo-Pacific is particularly attractive, sporting thin orange bands on its bright red legs.
It grows to around 5cm/2” and makes its home in the shells of venomous cone snails. It is also expensive, but well worth the money if you can get hold of one and can meets its needs.
Halloweens can be risky propositions for the reef aquarium and best kept in a system without delicate fish and invertebrates. Having said that, this predominantly nocturnal species can perform useful scavenging duties. Supplement diet regularly if there are insufficient quantities of scraps and leftovers for it.
Members of the Dardanus genus frequently crop up and the distinctive D. lagopodes or Blade-eyed hermit — pictured above by Alexander Vasenin, Creative Commons — from the Indo-Pacific grows to 6cm/2/4”. Its common name is inspired by prominent white eyestalks. The antennae are blue and legs a mottled white and orange, making this overall a pretty good looker.
While it is a useful scavenger it can be downright clumsy, which limits suitability for the reef aquarium. Many invertebrates don’t appreciate being lumbered over by this ungainly crab, but in the fish only or FOWLR system it can prove very useful.
The White-spotted hermit (D. megistos) — pictured by Alexander Vasenin, Creative Commons — grows to 10cm/4” and comes from the Indo-Pacific. This species is orange with white spots and hairy legs. It’s an aggressive scavenger and risky for reef aquaria. If opting to keep this hermit, feed regularly as they consume a surprising amount of food.
One of the most interesting species is the Anemone hermit (D. pedunculatus) — pictured here by Nick Hobgood, Creative Commons — from the Indo-Pacific. Growing to 6cm/2.4” this hermit has devised a clever strategy to protect itself from attack by octopus predators — recruiting anemones, with which it adorns its shell.
So reliant is the hermit on its cnidarian ‘bodyguards’ that it removes them from the old shell during house moving and relocates them on to the new one!
This appears a mutualistic relationship, both crab and anemone benefitting from this association. The crab manages to deter cephalopod predators, and the anemone hitches a ride with a very messy eater. The clouds of scraps generated by the hermit at mealtimes mean guaranteed food for the anemone.
The hermit has prominent spines on its legs and while smaller specimens can be beneficial scavengers on the reef, larger individuals can be extremely destructive, consuming a wide variety of invertebrates.
The Tiger hermit from the Indo-Pacific is one for the species system or aggressive fish-only aquarium.
It’s a true beast, displaying bright orange coloration and extremely hairy legs. Clocking in at 10cm/4”, this is a very aggressive species which will feast on any invertebrate it can get its claws on. This hermit is even capable of catching small unwary fish!
Hermit amongst the corals
There are those hermits that have totally done away with carrying a home and have taken a more permanent residence.
These sessile hermit crabs don’t scavenge about, but instead have adopted a filter feeding approach, using adapted antennae to sift tiny pieces of plankton and other particles.
They are frequently available for sale in Plume rocks.
War on the home front
If housed with conspecifics, some hermit species will fight over shells. As they grow they need to 'move house' to larger quarters and this can be a source of aggression between individuals.
If one individual has coveted another’s shell as a suitable ‘des res’ then it may rap its current shell on that of its rival. While the victim retreats in response, it may eventually become evicted if the aggressor can maintain an attack of sufficient intensity and duration.
However, if the aggressor is unable to maintain any momentum in its attack it will eventually give up.
A rock and a hard place
Not all hermits inhabit gastropod shells and some have exploited other forms of protection when molluscan real estate is in short supply.
Take the Sandstone hermits (Cancellus spp.) of Australia. These bore a hole into chunks of sandstone which occur in their native waters and once a large enough opening in which to place its body has been created the crab uses that hunk instead of a shell.
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It takes a truly dedicated worshipper to keep Tubastrea corals at their healthiest, warns Dave Wolfenden. However, the challenge is there should you wish to accept.
If in the mood for an unusual coral you might be interested in one of the Tubastrea sun corals of the Dendrophylliidae family. These non-photosynthetic invertebrates often look extremely attractive, but they can be very demanding...
There are several species in the Tubastrea genus, although identification is often difficult without an in-depth examination of any internal features, so it’s common for specimens to be identified to genus level only.
Many specimens in the trade seem to be T. coccinea, which has quite a wide distribution and appears to be frequently collected, although positive ID is sometimes challenging.
In any case, all species of the genus have more or less similar husbandry requirements. However, the Black sun coral (T. micracantha) appears particularly demanding and success with this species is often limited. The species is identified through its branching morphology and coloration which ranges from olive green to black.
Healthy specimens should exhibit tissue covering the entire colony, with any recession indicating problems.
Being non-photosynthetic, sun corals derive all their energy from food and they will quickly suffer with too little. Due to their large polyp size, sun corals rank among the easiest of non-photosynthetic corals to feed and they will accept a wide range of types — including surprisingly large morsels.
Frozen Mysis and Cyclop-eeze, as well as Artemia nauplii, are all suitable fare.
While a range of feed types is important to maintain optimal health, frequency is equally important and many enthusiasts find that sometimes feeding several times per day yields the best results. However, some people report success when feeding less frequently.
In any case, avoid leaving a gap of more than a couple of days between feeds.
Target feeding with a pipette enables the polyps to be individually supplied with food and will yield the best results.
A single colony will impose a relatively low load on the aquarium’s filtration capability, although heavy growth can necessitate an upgrade in skimming and filtration, or more frequent water changes.
Excess feed may also encourage Aiptasia rock anemones.
Being stony, sun corals construct a calcium carbonate skeleton and as such will need calcium levels maintained at similar levels to those required for SPS corals. Aim for 400-450ppm calcium and ensure phosphate levels are less than 0.03ppm.
Elevated phosphate levels are associated with excessive algal growth, which can smother the coral as well as compromising the formation of the skeleton.
Go with the flow
Sun corals naturally inhabit areas of moderate to high flow and this needs to be replicated in the reef tank. Adequate flow brings food to the polyps as well as supplying oxygen and keeping animal tissue clean, ridding it of mucous and detritus.
Laminar (sheet-like) flow will replicate the water movement which sun corals naturally experience.
Alternating flows could be an extra possible refinement to mimic natural tidal rhythms, although not essential.
They can be sited in areas of low lighting and, bearing in mind that sun corals are often found in caves or overhangs, specimens can also be placed upside down!
Being suspended not only lends them a natural look but helps to prevent the accumulation of detritus and sand which can lead to tissue damage. The potential for accumulated sand to harm Tubastrea corals means that a sand bed site is risky.
Despite the large polyp size, sun corals aren’t aggressive but avoid placing them near other corals which can sting them — especially LPS species and their potent sweeper tentacles.
Under ideal growing conditions, sun corals will readily reproduce by producing motile larvae called planulae which attach themselves to rockwork. Alternatively, the coral may reproduce by budding — forming tiny replicates of itself which eventually drop from the parent colony.
It’s possible to ‘frag’ (fragment, or divide) a colony. It sounds drastic, but just take a hammer and chisel or hacksaw to the colony. However, try to minimise damage to the polyps themselves when fragging a specimen, initially separating them with a craft knife prior to dividing the colony.
When first introduced to the aquarium, Tubastrea corals can 'sulk', refusing to open their polyps.
Be persistent to entice the coral into feeding, with regular offerings usually doing the trick.
Offering feed at regular times can sometimes encourage the coral to open its polyps at around the same time, presumably predicting feeding time.
The next big challenge
Maintaining non-photosynthetic corals is the ultimate challenge for many aquarists. While keeping sun corals is not beyond a number of hobbyists, success with many types of azooxanthellae invertebrate is proving elusive.
In this context, the term ‘non-photosynthetic corals’ includes a range of sessile invertebrate groups and soft corals of the Dendronephthya genus (pictured above), wire corals of the Cirripathes genus and Acalycigorgia gorgonians, among others, which have shown to be extremely difficult to maintain on anything like a long-term basis.
Some public aquariums have been experimenting successfully with specialised systems, but some of the greatest achievements have been made by dedicated hobbyists.
Azooxanthellae species are demanding for several reasons. Firstly, many specimens appear to need virtually constant feeding. Not only that, but the size of their polyps means that many species are dependent on specific particle sizes and mere Artemia won’t cut the mustard.
It seems that many rely on phytoplankton, with so-called marine ‘snow’ (detritus and mucous from bacteria, plankton and other organisms) also a possible important component of their diet.
Flow seems another crucial factor, with animals appearing remarkably sensitive to flow rates slightly outside a narrow optimal range.
It also seems that flow patterns simulating tidal patterns may be beneficial. Light levels are important, with animals affected by algal growth if lighting is excessive.
All this adds up to making non-photosynthetic corals far from a walk in the park and many who have achieved success possess set-ups bristling with automated feeding systems, delivering regular cocktails of food via peristaltic pumps, agitated courtesy of magnetic stirrers to maintain the feed in suspension.
All this feed input has potentially drastic implications for water quality. This necessitates large regular changes, again often automated by many diehard aquarists, along with some aggressive protein skimming.
Some of the most successful non-photosynthetic systems look stunning, but these are among the most high-maintenance of all aquaria. Fair play to those dedicated hobbyists able to keep such demanding specimens.
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Related to earthworms but far more attractive and interesting, these marine wrigglers have really caught Dave Wolfendenâ€™s eye.
Fanworms and feather dusters are among some of the most beautiful marine aquarium inhabitants. However, these bizarre creatures are frequently misunderstood and perhaps, ironically, increasingly high-tech developments in the hobby have made many aquaria unsuitable for them.
So what are these strange creatures, and what are their captive requirements?
They are actually annelids, which means they are related to earthworms. However, unlike the free-living members of that phylum, these worms are sedentary — in other words, they are sessile and fixed to a spot.
As with the earthworms, they have a segmented body, although it is protected within a tube. Two groups are of interest, both with slightly differing morphologies and habits. All worms of both groups live in tubes, however, and they have paired gills used for respiration and feeding.
The sabellids construct a tube from detritus and mucous — out of which they extend a bizarre but beautiful 'crown' of paired gill plumes known as radioles.
These trap particles and sort particles according to size. Larger ones are rejected, assisted by a mucous which helps the current to carry them away. Medium particles are used to help build the worm’s tube and the finest particles are ingested as food.
Tiny cilia — hair-like projections on the surface of the gills — move the particles along to the mouth.
Many sabellids are found living in the sand and mud on the seabed.
Serpulids, forming the other group, secrete a calcium carbonate tube and they tend to be found on hard substrates. In many cases they can be found living on corals, such as Porites species.
The worm initially burrows into the host, assisted by secretions of acid, and, if taking up residence on a coral, the host eventually overgrows the tube.
The paired gills of serpulids tend to assume a spiral-like morphology and the worm also possesses a nifty trapdoor mechanism known as an operculum. This is used to effectively shut off the entrance to the tube, making these worms extremely well protected.
Being suspension feeders, these worms trap tiny particles on their gills. To some extent, they can facilitate this through rhythmically pumping their gills, but a degree of water movement will be needed to help in feeding.
Water movement not only carries food to the worm, but also carries oxygen to the gills and helps the animal to shed mucus.
Sabellids tend to rely on laminar flow, which can be switched in direction to mimic tidal motion.
Serpulids are more tolerant of strong, chaotic water movement, presumably because of their habit of hunkering down in the skeleton of their coral host, which affords some protection.
Small particulate foods will be necessary and this can include phytoplankton, juices from frozen feeds and liquid invertebrate foods. Frequent feedings offer the best chance of success, but don’t go crazy, as some feeds can play havoc with water quality.
Target feeding of individual worms, using a syringe or pipette, may be a good approach.
The modern reef aquarium, with its aggressive skimming and low nutrient levels, are often not ideal for these worms, which benefit from regular supplementary feedings. Mature systems are preferred for captive worms, as these provide stable water conditions, as well as housing potential feed in the form of natural plankton populations.
Many fanworms have met a premature demise, courtesy of inappropriate tank mates. Just think how appetising those juicy fan-like gills must be to various fish, as well as many other invertebrates.
This means that puffers, most triggers, angels and many butterflyfish are no-no.
As for invertebrates, many crabs seem to find the gills and the tubes of these worms irresistible.
There are several genera of feather duster in the trade, including Sabellastarte, Bispira and Branchiomma, and to some extent they have similar requirements in terms of flow and feed.
Placement is important as, if conditions aren’t to the worms’ liking, they tend to leave their tube, often with dire consequences. However, they will occasionally relocate to a more favourable position and fashion a replacement.
They can be placed in the substrate, or among live rock. Some tiny species will be introduced as hitchhikers on live rock and may proliferate in the right conditions.
Of the serpulids, the Christmas tree worms of the Spirobranchus genus are the most familiar to aquarists. They are commonly seen embedded within imported Porites corals in the Indo-Pacific and other corals, such as Montastrea (star corals), may serve as hosts in Caribbean waters.
Spirobranchus giganteus, the horned Christmas tree worm, appears the most frequently-seen species, having a cosmopolitan distribution in all tropical seas.
Coloration of the plumes is highly variable and can be quite stunning. It’s easy to understand the appeal of these animals and, if you’re going to plump for Christmas tree worms, chances are they’ll be found on a coral host.
The best chance of success with the worms is to look after the host coral — so provide it with optimal water quality, adequate water movement and sufficient lighting. It also appears that the coral itself may provide some form of protection or benefit for the worm, so it’s important to meet the host’s needs. Ensure, too that the worms get regular feeds.
Don’t lift them out of the water
Be careful when acclimatising tubeworms. Ensure changes to water parameters are made gradually and, where possible, avoid lifting them out of the water as any air trapped in the tube could cause problems.
Can I breed these worms?
Both soft-bodies and calcareous tubeworms have been known to spawn in captivity, although the chances of larvae settling and surviving are slim. However, some sabellids will reproduce asexually in the aquarium under optimal conditions.
The crown: shed or dead?
Many fanworms will shed their crowns of feeding tentacles in unfavourable conditions. This may happen in response to poor acclimatisation techniques when introduced to the tank, or as a result of a drop in water quality.
Many aquarists will then discard the worm, perceiving this as terminal behaviour, but it’s worth bearing in mind that fanworms will regenerate the crown in suitable conditions.
Keep an eye on any specimens that have shed their crowns, but don’t be too hasty to get rid of them. Ensure water quality is suitable, feeding is adequate and the worms are not experiencing predation. With luck, they will recover.
Not for novices
On balance, fanworms are best avoided by newcomer aquarists. They’re not impossible to keep, but prior experience of maintaining water quality and meeting their exacting needs in terms of flow and feeding will be highly beneficial.
Aiptasia and Jeremy Gay are sworn enemies. Here he reveals how you can declare war on and kill the brown menace.
If there’s one thing that drives me mad about reef tanks it’s Aiptasia, or rock anemones as they are commonly known.
I’ve dealt with months of red slime algae, clownfish after clownfish jumping out, high phosphates, low KH calcium and magnesium, all of which are fixable — but Aiptasia makes me want to hang up my refractometer for ever and admit defeat.
What are they?
Aiptasia are small brown anemones, typically less than 2.5cm/1” in diameter, with tentacles and on a stalk.
Unlike desirable anemones, these are hardy, reproduce quickly and can sting other corals.
A new reefkeeper may mistake them for polyps, yet these can move, quickly reach plague-like proportions — and are also a boring brown!
How do they get in?
They just creep in unnoticed on the rocks to which the corals are attached, or on live rock.
Aiptasia are expert hitchhikers which can live in sumps and pipework. You may even get one or two hanging onto Caulerpa or Chaetomorpha passed on between fellow reefers.
If moving corals or live rock from shop to tank you probably won’t see them, but, once in your tank, give it about 24 hours and you’ll be stuck with them.
They’ll travel out of water too, on wet live rock, so you’ll easily miss them when placing your rock as they will be shriveled and/or retreated into a tiny crevice.
As we improve at reefkeeping and make our tanks even more suitable for corals, we also make life more agreeable for Aiptasia.
These organisms thrive under good light, holding brown zooxanthellae within their tissues and providing them with food, but they also do well at catching and eating zooplankton aimed at feeding corals or any other foods, even dry fish foods.
They aren’t fussy as to light spectrum or intensity, or water flow, and, even worse, tolerate really unreef-like water conditions such as high temperatures, high salinity, yet low calcium magnesium and alkalinity. So if you’re struggling and doing most of the things wrong you’ll most likely end up with nuisance algae and nuisance Aiptasia!
The way we set up our tanks helps Aiptasia too.
Natural filtration means less emphasis on mechanical filtration and stronger pumps ensure that particulate matter is always in suspension. They spread when there’s lots of food about and when conditions are to their liking.
They can sting corals into submission and then stretch over their victim’s spot. I’ve even seen them on the base of larger corals.
Run a sump-based system with refugium, kill off all the Aiptasia in your main tank and more will emerge from pipework and the refugium below. In this vicious circle its almost impossible to totally eradicate them.
Prepare to take up battle stations!
Failing in any prevous efforts to kill them may even leave you with more Aiptasia, so wise up on some of these tactics….
How can you kill them?
You cannot use copper in a reef system, as this will kill every coral, invert and critter in your tank.
Others measures include using Aiptasia treatments to kill them off outright or control them, or by using biological control like fish or inverts that are known to naturally predate anemones.
Use liquid remedies
These are the most widely available Aiptasia controllers. The idea with most is to inject a fluid either directly over or into the anemone at its stalk or disc.
Treatments tend to follow two main paths: by shock and awe using lemon juice or acid to literally blow up the anemone in its alkaline, salt water via sheer revulsion to the alien compound — or chemical warfare using calcium-based treatments which can sneak up to the anemone and smother it with a calcium overdose, or, if you’re lucky, injecting calcium straight into it, killing by calcium overload.
Both treatments will cause the anemone to immediately recoil into its hole and, as it expels water from its tissues, it will also expel as much of the alien fluid as it can in an attempt to survive.
I’ve tried most of the potions on the market and amazingly, almost all of my super-strong Aiptasia have survived, retreating into their holes for 48 hours before emerging victorious. They shouldn’t survive, but they do.
Failing that, use a multi-pronged attack. If you don’t kill one outright persevere over a week or so. All that anemone wants to do is come out and feed. Keep making life a living hell and you might just kill it.
Introduce a fish which eats Aiptasia for a living. However many aquarium-suitable Aiptasia eaters don’t really eat them in the wild, like the “Aiptasia-eating” filefish — and also if they’re tough enough to eat an anemone despite a mild sting, they’re probably going to favour your corals first.
The best are the Copperband butterflyfish (Chelmon rostratus) and the Aiptasia eating filefish.
Copperbands aren’t brilliant in aquaria, acclimatising badly in all but the largest, most naturalistic reef tanks. Some demolish Aiptasia populations in days, others don’t touch them, but will eat all those desirable fan worms and critters you want for tank diversity.
Because of their size they aren’t suitable in anything smaller than about 300 l/66 gal either!
Next is the new kid on the block — the filefish. Most aren’t reef safe because they eat inverts, so reefkeepers take a risk and add one to their tank in the hope that they will eat Aiptasia and leave their corals alone.
Sometimes they are successful, but other times will target LPS and soft corals and then be a nightmare to remove. I’ve even had some that ate nothing, despite optimum water, and wasted away surrounded by Aiptasia.
Risky alternatives (Pic above by Jenny Huang, Creative Commons)
You can go for even more predatory butterflyfish, like the Klein’s. These aren’t even reef safe, so you would need to either remove all your corals — risking recontamination when you returned them — or introduce them to an SPS-only reef tank where the polyps are out of sight for most of the day.
Even then a known anemone eater may not target the anemones and the stubborn starvation game is not one you can play with delicate butterflies or filefish. They will just die.
The most famous Aiptasia-eating invert is the Peppermint shrimp, (Lysmata wurdemanni) but there’s also the similar L. californica or L. boggessi to consider.
True Peppermints have a red tail and red body stripes, but many other species have black or blue tails with silver stripes surrounding the red stripes. Sometimes it’s not easy to tell, but a well illustrated reference book will help identify the real thing — or find an experienced reefkeeper who knows.
Even then you may find that Peppermints are secretive, nocturnal, and may not even eat a single one, or leave the large ones. If you start to lose desirable polyps afterwards that may down to the pepps too, and getting them out from under a rock won’t be easy.
Reluctant to eat?
Worst of all is when your Aiptasia-eating filefish, Copperband or Peppermint shrimp refuses to eat a single one. This can happen all the time, as they might prefer fish foods or other foods.
Should you starve them into taking this anemone? No, as both fish species won’t survive anything less than very regular feeding, so you’ll just end up with corpses.
On the subject of eating I was amazed at what the anemones themselves can eat. I sat and watched once while a large Aiptasia caught the flailing polyps of my Pulse coral, cut them off and promptly ate them.
If you’re feeling particularly nasty another way to kill these pests is with putty. Basically you get a small blob of reef putty and then block up the hole in the live rock into which the Aiptasia has retreated. Just check there isn’t another hole connected to it first.
A tiny issue with this is that live rock always open in structure, not sealed at every orifice.
Don’t let them in!
This tactic seems obvious, but for reasons I’ve explained, Aiptasia can hitchhike into your tank on nearly anything. As with all fish purchases, quarantine your live rock and coral for a couple of weeks first and look particularly closely for rock anemones. If you happen to find one it will be much easier to treat on a small lump of rock than on a full-blown reefscape.
Train your shrimp to do the job
I spoke to one retailer who had trained his Peppermint shrimp to eat Aiptasia exclusively, before selling them on to the public.
He therefore needed a ready source of his own, farmed Aiptasia and to breed them he would annoy them by stabbing and knocking them with sharp implements. They would then release their planulae which would grow on into adults.
So the moral of this story is if you manage to annoy your Aiptasia without actually killing them, they will simply produce more! Trained shrimp sounds like a good idea!
Try Berghia too
Berghia are nudibranchs (sea slugs) which are meant to prey exclusively on Aiptasia. They’re pretty tiny and when bought mail order may be as small as a grain of rice, so are fiddly and, once introduced, you may never see them again.
They should solve the problem, but when I added three to my 0.9m/3’ reef tank the Aiptasia reproduced more quickly than the tiny slugs could eat them. I guess I need more and of a larger size!
They won’t prey on anything else though, which is something of a bonus, and are cultured in captivity.
Top pests: Aiptasia versus majano
Majano anemones are pests too. I regard these as much more pretty than Aiptasia but they become invasive across the rock structure, spreading and overgrowing everything.
Physically remove them with tweezers in their early stages of growth — although I don’t put their level of terror quite as high as Aiptasia.
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Dave Wolfenden investigates anemones â€” creatures with a reproductive method thatâ€™s pure science fiction.
Anemones are among the most fascinating of the ocean’s inhabitants — and who could fail to be inspired by the beguiling sight of a huge carpet anemone and its clownfish symbionts?
Not only are they fascinating, but when the creature’s pedal disc becomes lacerated a dropped shard of body tissue can create a new individual on the substrate. It’s a reproductive strategy which sounds straight out of a John Carpenter film.
Anemones can be among the more challenging of inverts, with many requiring very specific conditions in aquaria.
Anemones are cnidarians, a group including corals and jellies. They have radial symmetry and tentacles with batteries of nematocysts (stinging cells) around a central mouth. The creature itself will either anchor to a hard substrate or burrow into sand or mud sediments using its pedal disc.
The anemone’s morphology may vary depending on adapting to habitat, although the fundamental body plan remains constant. Many tropical ones live with zooxanthellae and several species are themselves symbiotic with many animals other than clownfish!
Anemones can have demanding parameters and will shrivel and 'sulk' if conditions are not to their liking. They need optimal water quality, along with oxygen levels as near saturation as possible. Effective skimming is therefore highly desirable.
A mature system is preferable, as any spikes of ammonia could be disastrous. Most popular species are hermatypic, housing zooxanthellae as symbiotic algae, so suitably intense, 'reef quality' lighting is necessary.
Adequate water movement is essential to carry oxygen and food to the anemone and rid it of wastes.
A direct blast from a powerhead would not be appreciated, but chaotic flow patterns are ideal. Also ensure that intakes for any pumps and powerheads are screened to prevent roaming anemones getting sucked in.
When choosing one it should appear 'inflated' and plump rather than shrivelled and covered in mucus.
Examine the pedal disc for signs of trauma – as most physical damage during capture occurs here. If there’s evidence of damage, don’t buy. Acclimatisation should be very slow, using the ‘drip’ method over a couple of hours or so on introduction to a new system.
Avoid taking an anemone out of the water during this process and do not introduce any transport water as this is liable to be ammonia rich.
Some aquarists strongly deny anemones need any supplementary feeding, but others maintain that feeding is necessary to promote health and growth.
Many species will do fine without any supplementary feeding if kept with other invertebrates and a few fish, sustaining themselves on leftovers. Having said that, the Carpet anemones (Stichodactyla spp.), being aggressive and predatory, may benefit from finely-chopped meaty foods twice a week — but be cautious rather than risk pollution through overfeeding.
Many anemones will discharge 'pellets' of partially digested foods. These are a pollution risk and should be removed.
Separate sexes are encountered in many species and reproduction may be utilised. Male and female gametes are released through the mouth in a co-ordinated manner. The resulting eggs develop into motile planula larvae, which find a suitable substrate on which to develop into a polyp.
Asexual methods are also employed. Budding, or the formation of tiny replicates of the parent plant, may be seen in some species. Alternatively, binary fission, during which the anemone splits in two, can be used.
Many anemones are added to existing reef aquariums stocked with corals and other sessile invertebrates, but this isn’t always successful as they may employ ‘chemical warfare’ against heterospecific cnidarians and conspecifics. They are also carnivorous, so many small fish and mobile inverts are fair game.
Bear in mind too that many fish species will naturally peck at anemone tentacles, so never house them with butterflies, large angels, triggers or large puffers. Careful choice of tank mates is therefore essential and mixing anemone species and conspecifics requires plenty of room.
Dyeing is still the dark practice
Some exporters dye various anemone species, such as Heteractis crispa, in a range of outlandish colours.
Although many anemones are available in stunning natural morphs, the practice of dyeing persists. This dooms many anemones to a premature death — even though the animals are beautiful enough without any such enhancement.
Buy only from a reputable dealer who knows the history of his or her stock.
What's available in the hobby?
Heteractis crispa, the Sebae anemone, reaches 45cm/18” and has long, thin tentacles with a pink dot at the centre of each. It attaches to a hard substrate and is reasonably hardy. Many species of clownfish will symbiotically associate with this Indo-West Pacific anemone.
H. malu, the Malu anemone, is an Indo-Pacific species with a relatively long ‘stalk’ buried in the substrate. Highly variable in coloration, this reaches around 20cm/8”.
It symbiotically associates with several species of clownfish.
H. magnifica, the Ritteri anemone, is another symbiont and unsuitable for most captive systems, requiring several hundred litres as it reaches 1m/3.3’. It attaches to a rocky substrate and is quite mobile.
This demanding Indo-Pacific species, requiries exceptional water quality, brisk water movement and intense lighting.
Condylactis gigantea, the Giant Caribbean anemone, grows to 30cm/12” and is naturally found on rocky substrates in shallow water.
Clownfish don’t naturally associate with this anemone, as there are none native to the region, although some species may form unnatural partnerships in the aquarium. Nevertheless, many species naturally act as symbionts, including Periclemenes shrimps, Mithrax crabs, Arrow crabs and many others.
This is a relatively demanding anemone in terms of lighting.
Entacmaea quadricolor, the Bubble-tip anemone, from the Indo-Pacific is hardy, relatively inexpensive and makes a great host for many clownfish species, as well as Periclemines shrimps and Porcelain crabs of the Neopetrolisthes genus.
Although its common name is inspired by often bulb-tipped tentacles, many specimens don’t exhibit this characteristic. This species is available in a variety of colour morphs, with the stunning red desirable and expensive.
Bubble-tips will, in optimal conditions, readily undergo binary fission in the aquarium.
This species is fairly undemanding in terms of lighting and adapts well to a range of intensities. It’s the best first-time anemone, growing to 30cm/12”.
Carpet anemones are impressive, with some species growing to more than 1m/3.3’. Their sheer size and aggression mean they should be taken on only after careful thought and planning.
Any aquarium environment must meet some exacting needs and it’s equally important that the existing species mix of your system doesn’t fall prey to this feisty cnidarian.
The Giant carpet anemone (Sticholdactyla gigantea), needs a minimum of 500 l/110 gal, with an expansive sand bed at least 10cm/4” to burrow into as well as some form of hard substrate.
Carpet anemones will consume a wide variety of fish and invertebrates, even the occasional clownfish! Despite this, they can play host to clownfish and Threespot domino damsels (Dascyllus trimaculatus) as well as Periclemenes shrimps.
Careful planning is key here so maintain Carpet anemones as part of a dedicated system —limiting invertebrates and fish to a minimum while including 'tried and tested' symbionts.
The following three species are all Indo-Pacific in origin.
S. gigantea grows to 1m/3’3’ and is available in a range of colour morphs. Expect to pay top dollar for more 'exotic' ones. This species requires solid substrate in addition to a sand bed.
Haddon’s anemone (S. haddoni) grows to around two-thirds the size of S. gigantea and requires a relatively deep sand bed. This species is also seen in a range of colour morphs.
Merten’s anemone (S. mertensii) differs from the previous two in requiring a rocky substrate. Reaching sizes greater than S. gigantea, this species is infrequently collected. When available, specimens carry a hefty price tag but are nevertheless quickly snapped up.
The Cerianthus tube anemones are sometimes offered. They are so named due to their habit of constructing a tube, courtesy of specialised cells.
These anemones are undemanding in terms of lighting and relatively subdued conditions are preferred. They require a sandy substrate in which to burrow and take care when homing them with small fish species, as even clownfish may be eaten!
Most common in the trade is the Indo-Pacific C. membranaceus which grows to 20cm/8”, although some coloured species may be offered — usually identified only to genus level.
Bartholomea annulata, the Curlycue or Corkscrew anemone, grows to 15cm/6” and is characterised by curly-looking tentacles. Hailing from the tropical West Atlantic, this species is cheap and cheerful. It tolerates lower lighting levels than many anemones and is of the same family as Aiptasia, the rock anemone.
It’s less problematical, however, but can be aggressive towards other invertebrates. It lives in association with Alpheus armautus shrimps in the wild.
Jeremy Gay shows you how to shrink a classic reefkeeperâ€™s coral aid to suit the smaller tank.
This month’s project highlights key aspects of the modern marine hobby — the facts that our tanks are getting smaller and that many more of us are now propagating our own coral frags, which is great for the environment.
The concept of a coral rack made from plastic egg crate isn’t new. TMC distributes a wonderful acrylic and egg crate rack made by Schuran but, only being offered in one size, it won’t fit all tanks and is typically best used in aquaria of 0.9m/3’ or more long and 0.6m/2’ front to back.
I bought a 120 x 60cm/4 x 2’ piece of egg crate from TMC and decided to set about making my own four-tier version that will fit inside a nano marine tank just 40cm/16” long.
This simple plastic staging enables you to place corals so they all receive adequate light and water flow, and won’t sting each other by touching.
Unlike live rock the racking is stable and level, so you can place coral frags on an even surface and they won’t fall over.
Better still, you can also get special fragging plugs to poke into or clip on top of the egg crate, giving you an even firmer fixing.
A powerhead can be placed in the racking to stop dead spots forming underneath and, if a fan of sloping rock wall formations, you can cover the whole rack in live rock so you won’t need base rock. Again a powerhead can be placed in the pile to prevent dead spots. All in all, this is a very useful bit of kit.
What you’ll need
Some egg crate, in this case about 60 x 60cm/2 x 2’
Pliers to cut it
About an hour
Cost at a glance:
I bought a large sheet costing £39.95, but only needed half of it. Smaller sheets are available, so budget for around £20. Cable ties cost £2 and I already had the pliers and pen.
Aesthetics aside, the rack is a great invention and a big help when culturing corals.
Egg crate is brittle. When cutting it you’ll want to wear goggles to stop pieces snapping off and hitting you in the eyes.
Here's how to make your own
1. Mark it out
Indicate your uprights. I’m counting 16 squares across and 16 high. I create steps at four square intervals on the diagonal edge.
2. Snip with pliers
Poke through and start snipping. You have to squeeze quite hard but will soon get the hang of it. I want three uprights for strength.
3. Cut your platforms
Snip again, this time to make the platforms. This is when you determine the length of the racking, making it as long or short as you like.
4. Cut and fit back support
For extra strength I cut out another strip of crate to be strapped to the back. This will easily support the weight of any rocks.
5. Secure with cable ties
Cable ties fasten the support to the vertical uprights and the whole structure becomes sturdy and strong.
6. Place the platforms
Position the horizontal platforms on the racking. Again these can be cable tied or just placed on to the structure for easy removal.
This side view shows the sturdiness of a plastic-framed four-level structure that offers enough level space to prevent frags falling and stop them stinging by touching each other.
All aquariums need creatures that get rid of the muck and algae that threaten the health of your set-up. Hereâ€™s Levi Majorâ€™s guide to the best marine cleaners in the businessâ€¦
Live rock in your tank should include some basic critters, such as worms, amphipods and maybe micro brittle stars, to help with the detritus. However, you need to supplement them — and that’s where the clean-up crew come in.
These are the reef inverts that live in their millions and clean the ocean floors, faces of reefs and all the nooks and crannies in between.
Mithrax crab(Mithraculus sculptus)
Also known as the Emerald crab, Mithraculus sculptus consumes leftover meaty foods and many nuisance algaes. Unlike many other animals, the Mithrax will eat bubble algae (Valonia sp.) and help clean your aquarium.
Native to Caribbean reefs, the Mithrax is easily identified by its distinct, flat shiny green body and hairy legs. Being nocturnal it hides in caves and among rubble during the day, but, provided with plenty of rockwork and associated hiding places, will venture out during the day to forage.
This opportunistic feeder may turn to corals, invertebrates, coralline algae or small fish should there be an inadequate supply of food in the aquarium.
Supplementing its diet with dried seaweed and chopped meaty foods, such as shrimp, and initially limiting numbers to a maximum of one crab per 100 l./22 gal. of tank volume will hopefully ensure that they remain well fed and become a model scavenger.
Range: Atlantic, Caribbean
Size: Maximum. 8cm/3”
Reef compatible: Yes
Tank conditions: 22-26°C/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
Hermit crabs (Paguristes cadenati and Clibanarius tricolour)
Numerous species of 'dwarf' hermits are suitable members of a clean-up crew. While all are becoming more available, the two most commonly seen are Paguristes cadenati and Clibanarius tricolour.
P. cadenati, or the Scarlet reef, or Red legged hermit crab (pictured at the top of the page) has red legs and a yellow face. It’s found along the reef faces and coral rubble of the Caribbean and Western Atlantic where they busily scavenge for organic matter and algae.
This crab best kept at a ratio of one per 25 l./ 5.5 gal. in an aquarium where it will have ample supplies of algae and detritus. Red legged hermits are useful for keeping algae, including filamentous algae and cyanobacteria, under control.
As well as algae, these eat as much uneaten food in the aquarium as they can find.
Range: Indo-Pacific, Caribbean, Western Atlantic
Size: Up to 4.6cm/1.8”
Reef compatible: Yes
Tank conditions: 22-26°F/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
Clibanarius tricolor, or Blue leg hermit crabs, are superb algae-liking scavengers, just like their red legged counterparts. Because of their particularly small size they can get into areas of the aquarium and live rock that are usually difficult to reach.
However, C. tricolor is known to occasionally attack snails or other hermits in order to steal their shells. It’s therefore important to provide extra shells in your tank to try and prevent at least most incidents of theft.
Size: Up to 2.5cm/1”
Reef compatible: Yes
Tank conditions: 22-26°C/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
Peppermint shrimp (Lysmata wurdemanni)
Known to manage nuisance Aiptasia anemones, this brightly coloured shrimp has a transparent body with red longitudinal bands, but can easily be mistaken for similar looking species such as L. rathbunae. Having only subtle differences it is easy to see why some Peppermint shrimps eat Aiptasia, while others don’t.
This is only part of the story. If discounting L. rathbunae by choosing those with a darker tail, showing no real discernable striping and a generally darker, more opaque body, we are more likely to have the true Peppermint shrimp. Even so, some individuals may show no interest in Aiptasia.
Considered easy going and largely sociable with its own kind, it may fight other species in an aquarium. Some may nip at soft corals, others be model inhabitants.
Peppermint shrimps are shy, seldom venturing from rockwork. Given time, adequate conditions and food they should be seen more frequently.
Appetite for Aiptasia aside, Peppermint shrimps are valuable scavengers, picking over live rock to consume detritus, uneaten food and decomposing organic material. They can also be prolific breeders, always adding to the aquarium’s food web.
While possible to rear the progeny, it’s not simple to raise the larvae through various stages of development.
Size: Up to 5cm/2”
Reef compatible: Yes
Tank conditions: 22-26°C/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
Snails (Astraea and Trochus)
Snails could be seen as essential in any healthy reef aquarium, but choosing the most suitable and judging how many you should have requires consideration.
The two generally accepted as forming a major part of any clean-up crew are Astraea and Trochus. You could also include Turbo snails, but their particularly large size and associated ability to tumble corals or indeed rockwork should be taken into account.
Turbo fluctuosa is native to the Gulf of California, off the coast of Mexico. It thrives in crevices and holes in natural reefs and in the home aquarium needs ample hiding places among live rock and large spaces to graze.
This snail is popular due to its ability to mow vast areas of nuisance algae. Being particularly fond of hair algae, cyanobacteria and diatoms, a single individual can take large quantities and other algae from your live rock and glass.
If limited to one per 100 l/22 gal they are efficient grazers and may require supplementary feeding with dried seaweed.
Range: Circumtropical and temperate
Size: Up to 7.6cm/3”
Reef compatible: Yes
Tank conditions: 22-26°C/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
Astraea snails (above), which have tan to olive green conical shells with pronounced ridges, are particularly useful for clearing brown and green algae films from aquarium walls.
They are capable of controlling filamentous algae, but to a lesser degree than T. fluctuosa.
Lithopoma tectum, formerly Astraeca tecta, are more at home on live rock and move between the rockwork and glass. However, as they can’t right themselves if they fall they can be preyed upon by hermit crabs or other scavengers.
Because of their voracious appetites, stocking at one per 100 l./22 gal. and monitoring whether additional snails are required would be appropriate.
Size: Up to 2.5cm/1”
Reef compatible: Yes
Tank conditions: 22-26°C/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
Trochus sp. snails (above) are fantastic algae eaters and are adept at controlling a wide range of algae, cyanobacteria and diatoms in the aquarium. Unlike Astraea, Trochus are able to right themselves should they fall upside down.
There are several Trochus species, but the best known is the Banded trochus from Indonesia.
Prolific breeders, Trochus snails reproduce by releasing gametes into the water column and are well suited for reef aquariums if kept at one per 50 l./11 gal.
Size: Up to 2.5cm/1”
Reef compatible: Yes
Tank conditions: 22-26°C/72-78ºF; sg 1.023-1.025; pH 8.1-8.4
Care level: Easy
The choice is up to you!
This is no definitive list of cleaners, but should at least touch on the more popular species available and each one is capable of doing certain functions better than others.
Some come from waters you are not catering for, so choose what’s suitable for your needs. I’ve been conservative with stocking ratios to help you see what one or two of a few species can accomplish.
What to avoid
Other than those already recommended, many more invertebrates can help clean up — but some species are best avoided. These are particularly unwelcome:
Large hermit crabs (Dardanus, Aniculus, Trizopaurus)
Bigger crabs such as the Anemone hermit (Dardanus pedunculatus), Hairy hermit (Aniculus maximus) and Halloween hermit (Trizopagurus strigatus) are best suited to species-only aquaria.
These can be very disruptive creatures, climbing everywhere with their large and bulky shells dislodging corals or loose rockwork.
They are also renowned for attacking or eating any other tank inhabitants, if given sufficient oportunity.
Sea apples and cucumbers (Pseudocolochirus)
Commonly imported sea cucumbers belong to the genus Pseudocolochirus, with the most common species being the Indonesian Sea Apple (P. violaceus). This and the more colourful Australian sea apple (P. axiologus) are obligate filter feeders and use tube feet to attach to substrate in areas of high flow.
This allows them to expose their feeding tentacles to the greatest amount of flow, so they can collect suspended organic particles.
These brightly coloured sea cucumbers are popular because of their beautiful patterning. However, sea apples are toxic and display the fact with bright colour patterns.
Potent chemical defences are often the last resort of these animals, but the demise of an individual may lead to the release of holothurin and holotoxin, which can be extremely toxic to fish and other inhabitants in an enclosed aquarium.
The release of their equally toxic eggs can lead to the demise of all fish in the aquarium.
Dancing shrimps (Rhynchocinetes uritai)
This is also known as the Camel or Candy shrimp and distinguished by a moveable rostrum or beak. It has a variable pattern of red and white body stripes and males tend to have larger claws (chelipeds) than females.
It’s a social shrimp which congregates with others of its kind in rock crevasses, under overhangs, or in the coral rubble.
It usually tolerates other shrimps, but may nip colonial anemones, disc anemones and soft leather corals, so cannot be considered strictly reef safe.
Arrow crabs (Stenorhynchus seticornis)
The Arrow crab is nocturnal, rarely seen during daylight. It’s fearless, even of its own species, and as such can be territorial. Two should never be housed in the same aquarium, as they are likely to fight to the death — the winner eating the loser.
This crab has eight spider-like legs and has a head pointed at the tip, like an arrow. The legs can be more than three times its body length, being perfect tools for hunting favourite foods.
Capable of decimating the bristleworm population of an aquarium, they can soon turn their attentions to other more desirable polychaetes and small fish.
Alex Correa explains all about the purpose of live rock and offers a step-by-step guide to making your own artificial hard stuff...
The popularity of reef aquariums has been responsible for much global investment this past decade. Some ideas and systems have changed, but always stable is the concept of live rock, supporting, as it does, the beneficial bacteria that’s needed.
Natural or artificial, it represents the most important component of natural marine systems.
The live rock environment reveals an amazing interactive world and relationships between crab and coral can often be seen providing mutual protection against organisms from the rocky substrate.
Unfortunately live rocks are still collected from reefs which are under increasing threat. When removing a natural resource from any environment a natural or artificial replacement is needed — unless that resource won’t be harvested further.
As for live rocks, when we remove the material from the ocean the natural re-formation of any more could take at least three to five years — and that depends on many issues.
We need to face some key questions. What exactly are live rocks and how much do we need them? Are we dependent on natural live rock harvests? What’s the difference between natural and artificial live rocks? Can we maintain a healthy reef tank with just artificial live rocks for any length of time? How do we make artificial live rock and what with?
Artificial live rocks have been recently introduced into the market and artificial live rock can be ‘seeded’ in the ocean.
In places like the Hawaiian islands, where I live, this is now the only way to legally keep an aquarium with live rock.
The nitrogen cycle
One of the most important factors in aquarium keeping is the nitrogen cycle. It determines the success of keeping organisms in closed systems for long periods without huge water changes.
The nitrogen cycle works with two distinct transformations — nitrification and denitrification — and are undertaken by many different types of bacteria.
Nitrification is completed in two parts. The first involves the transformation of ammonia to nitrite and the bacteria responsible are Nitrosomonas, Nitrosospira, Nitrosococcus and Nitrosolobus, among others. These are aerobic, meaning that they all need oxygen to survive.
The bacteria will colonise all suitable aerobic surfaces which water comes into contact with when there’s good flow.
The second part involves another group of bacteria responsible in converting nitrites and breaking them down into nitrates. The bacteria responsible are Nitrobacter, Nitrosospira, Nitrocystis, Nitrococcus and others.
Nitrites are toxic to some living organisms and enough of them can do serious damage to many in a closed system. They can inhibit oxygen uptake in a fish’s bloodstream but in a fully cycled aquarium are kept in check by the helpful bacteria.
Nitrates have less negative influence because they are less toxic than nitrites. Nitrates are also basic nutrients feeding algae that can attack invertebrates, like the corals. They should be kept under 5ppm to avoid water pollution and algae overgrowth.
This particular waste product of nitrification can be removed by denitrifying filters, protein skimmers, water changes or uptake by algae filtration.
The other cycle is denitrification. The many genus of denitrifying bacteria normally found in closed systems are Micrococcus, Pseudomonas, Denitrobacillus, Bacillus, among others.
These bacteria live in a low oxygen environment, as inside a porous live rock or in deeper layers of the sand bed.
The bacteria consume nitrates and convert it into nitrogen gas, which is released through water movement and aeration.
Once we get to understand the nitrogen cycle, we know the importance of live rocks in marine aquaria. They support the live bacteria to do that job for us.
Real versus fake
Natural live rock works more efficiently than any other media available because it supports a constant interchangeable system of micro-organisms. Artificial live rocks can be similar and mutual qualities can be achieved if certain steps are followed during the construction, curing and seeding.
So, what’s the difference between the natural live rocks and the artificial variety? Apart from composition, the main difference between home-made and natural reef rock is the diversity of organisms found on them. Such differences can also be apparent among natural live rocks from distinct areas.
Both types will support bacteria for the nitrogen cycle. The quality of the calcareous material used
and manner in which we make the artificial rock will determine the areas to be colonised by bacteria, among other organisms.
Basically, a porous structure will help the development of greater numbers of bacterial colonies.
Natural rocks will introduce undesirable organisms into the system, like Aiptasia spp. anemones, Mantis shrimps,
fire worms and others.
With artificial live rock we can have what we want!
Saltwater aquariums planned to become natural systems, with any alternative for natural filtration, do not depend on natural live rock. Natural systems are related to the type of natural filtration by bacteria and not dependent on natural structures from coral reefs. Any organism can be introduced to an artificial live rock structure.
Mantis shrimps, for example, are regularly introduced in aquariums with natural live rock. With artificial live rock you can avoid such dangerous organisms.
How to 'seed' the rocks
Your new artificial live rock will be ‘dead’ because as yet it contains no living organisms, so you need to put them in.
‘Seed’ it by putting it on a natural live rock so organisms can migrate. Then wait and see the changes over the next few months.
The rocks I make are not seeded with natural rocks, but with a selection of organisms applied to the concrete rocks. This way, undesirables are not introduced.
Introduction of the organisms depends on size and body structure. To apply hard corals use underwater epoxy cement. For soft corals and zoanthids use a ‘superglue’ gel, making sure the base of the organism is dry before application, then place underwater and quickly but gently press the polyp or colony to the desired rock.
You need to find the right crevice or hole for sponges — and avoid exposing them to the air, as they are very sensitive.
Excellent seed choices include worms, copepods, amphipods, algae-eating snails and sea cucumbers. Scraped coralline algae can be spread for a faster overgrowth and water movement can help it flourish.
Attractively coloured, coralline algae normally indicate that a system is mature. They can also be seeded to the system, even without natural live rocks. Just scrape from any hard structure and sprinkle over the rocks.
Amphipods are among organisms that can be introduced with artificial live rock and they help control undesirable algae.
Coralline algae need various types of elements and compounds in order to thrive. Many are introduced through water changes, but they need to be maintained to promote coralline algae growth and reproduction.
We add certain elements to try to help coralline algae, including iodine. Normally we use potassium iodide solution as iodine is needed by both algae and invertebrates, but an excess could be undesirable in closed systems.
Calcium helps and the best way to dose is via kalkwasser mix (calcium carbonate). Other additives include calcium chloride and calcium reactors (kalk or CO2).
Corals with hard skeletons and bivalves also use calcium. In systems without such invertebrates, calcium additions are often unnecessary for coralline algae growth.
If the calcium rate drops in any coralline algae-only system add small amounts. Levels in a reef tank should be at least 380 mg/l.
Strontium is important and, together with calcium and magnesium, can be added as strontium chloride. Strontium levels in ocean waters are normally between 8 to 10 mg/l.
Magnesium won’t normally be needed. It is replaced with water changes in high enough rates for coralline algae and coral growth when natural water or quality artificial salt mix is used. The usefulness of other additives to help coralline algae is still speculative. Some include vitamins B1, B12 and C, trace elements and amino acids, but should be applied with caution.
Coralline algae prefer between 24-26°C/75-79°F and minimum alkalinity of 8 KH (2.9 meq/l).
The experimental system pictured above uses only artificial live rocks to maintain biological filtration and form the reef’s structure. This proves that calcareous materials and concrete are successful.
Artificial rocks need no maintenance. Once mature, presenting no danger with pH fluctuation in a saltwater environment, they will act as regular natural live rock.
How to set up for an artificial live rock tank
1. You’ll need coral sand, cement, buckets, a plastic tub, trowel, spray gun and water.
2. Start by mixing one part of cement to two or three parts of coral sand.
3. Add water and mix, making sure it’s not too wet. Next, get more coral sand and pour it into the tub to use as a mould.
4. Make a hole in the coral sand you’ve poured into your tub and add the cement/coral sand mix from the bucket. Start by mixing one part of cement to two or three parts of coral sand.
5. Make the holes on the rock, using sand between the concrete layers. You could also add salt to make the rock more porous.
6. Make a rough rock shape from the cement mix and then cover with more coral sand.
7. Spray with water immediately after finishing and spray again over the next 24 hours to make sure the mix is well bonded.
8. After 24-48 hours carefully remove the rock from the sand and rinse off the excess with water.
9. The calcium hydroxide in the cement will cause a high pH. Soak for up to 60 days, or until the pH has dropped to 8.3.
10. Scraped coraline algae can be spread over the structure for fast overgrowth. Water movement helps it grow.
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Donâ€™t be taken in by the striking colours of nudibranchs. For many reasons the hobby isnâ€™t ready for them yet, says Nathan Hill.
Part nudist, part foot, part stomach. That’s what it is to be a nudibranch. Some of these casually termed sea slugs are brightly coloured, some drab, some camouflaged, some brightly so — but all are incredibly hard to keep.
Nudibranch literally means naked gills. The feathery growths sprouting from their back are just that. These will be paired, or in the case of aeolid nudibranchs, numerous and tubular.
In an aeolid, like the one above, these tubes are known as cerata, and come in many forms; from spindle shaped to heavily branched. Some aeolids will even fill their cerata with the zooxanthellae of their prey, using the photosynthetic algae in the same way as their former victim had to produce sugars for themselves under intense sunlight.
It’s quite misleading to call all nudibranchs ‘sea slugs’. Yes, a nudibranch is a sea slug, but a sea slug need not necessarily be a nudibranch!
All of them belong to the class Gastropoda, a grouping that includes the humble snail, but the nudibranchs gave up their shell many millions of years ago, instead relying on stings, toxicity or foul taste to protect them.
Gastropod literally means stomach foot and never was a description more apt. There’s the foot, there’s the stomach, but not much more. ‘Sea slug’ simply refers to any gastropod without a shell that happens to live in the sea and the variations can be huge.
Unless camouflaged, nudibranchs are unmissable, and even the camouflage is garish. Their bright coloration serves as a warning to would-be predators of elaborate defence mechanisms.
Some simply taste awful, like the elegant Spanish dancer, a highly motile, free-swimming species. Some go so far as to generate their own sulphuric acid. Yet others will store up the painful nematocysts — the stinging cells of their prey — in their own bodies, making a painful arsenal of weaponry ready to fend off the curious and hungry. One species even makes a living tracking down and consuming the famed colonial hydrozoan Portuguese Man-o’-War feared for its potentially lethal sting.
The colours should also act as a warning. They can sting and bite you, especially in the wallet. You’ll be attracted, you’ll fork out good money and you’ll regret it.
Nudibranchs are bad news for both retailer and fishkeeper. It’s bad for the retailer, as if he or she is stocking them it speaks volumes about their ethics. It’s also bad for the aquarist, as after much fruitless searching and struggling you’ll find this animal way beyond your means. Nudibranchs make poor tank inhabitants.
In part this is down to a very specific dietary requirement, varying from species to species. Some are cannibals, feasting on other nudibranchs. Some will prey on fish.
The vast majority have evolved over millions of years to feed on one particular variety of sponge, coral, anemone or hydroid. Some will simply sit and excrete enzymes, sucking in the resultant digested slurry of their unfortunate victim.
Assuming you’re lucky enough to find out what your particular species feeds on, I wish you the best of luck in tracking down a ready source. It’s not uncommon for the food species to be far more delicate than even the most expert reefkeeper could accommodate, let alone undertake as a project.
Beware the store that informs you that these animals can be ‘weaned’ on to other foods. These cannot undo millions of years of fine tuning overnight.
Starve to death
However, there is a notable exception: Berghia verrucicornis, which is marketed heavily as the Aiptasia-eating slug. This species does exactly what it says on the tin, munching on those pesky anemones with gusto. Yet all good things come to an end and, on gorging, clearing out the tank and breeding, these animals will then simply starve to death.
I tend to see most animals as an end in themselves, rather than just a means to an end. Why risk the starvation of these hapless helpers when Peppermint shrimps will do just as good a job — and without the unfortunate end result?
Berghia come with other problems, too. They are small, even by nudibranch standards. Pop them into a heavily stocked reef tank and a hungry bristleworm or inquisitive crab may have ideas about their future. Being aeolids, Berghia can actually shed their cerata in the same way that certain lizards may discard their tails when threatened. However, for the ravenous crab with a pincer full of nudibranch that makes little difference.
For most of us an experience with a nudibranch will be accidental, perhaps as a by-catch brought in with a piece of live rock, or hiding under a purchased coral, to emerge, bemused and hungry once safely back among familiarity.
Such cases are particularly unfortunate and fishkeepers in such situations should do all they can to find at least some constructive information about these hapless stowaways.
It’s unlikely, but if you can find what they eat, and a source for it, then you could at least make the effort for them. There are many nudibranch forums and scores of websites dedicated to them, so you may get lucky.
What’s my stance on these creatures? Don’t bother keeping them. The nudibranch is a stunning and highly specialised life form that belongs in the oceans. Perhaps one day, with advances in technology and food production techniques, we may be able to venture into nudibranch keeping, but for now they represent one of the great taboos of the industry.
Slugs of the high seas
Not all nudibranchs are true to their usual ‘slug’ behaviour. As well as throwing off the shackles of a shell, some species have even done away with a benthic, ground-dwelling existence, taking to the open waters in their search for food.
Possibly the most extreme oceangoer is Glaucus atlanticus, otherwise known as the Blue sea slug or Sea swallow.
This species spends its life belly side up at the surface, ingesting bubbles of atmospheric air to maintain buoyancy. Although there’s debate as to whether it actually swims, this creature happily drifts across oceans, using the same countershade strategy as many pelagic fishes; light side up, dark side down.
Glaucus is a predatory carnivore, feasting on animals that most other creatures would do well to avoid. High on the menu is the deadly Portuguese Man-o’-War that also drifts the oceans, but trails tentacles and is feared for its powerful stings.
Not only does Glaucus have immunity from these stings, it positively relishes them, absorbing the dangerous cells — the nematocysts.
It stores them inside its own body, on the ends of the finger-like cerata that jut out either side of its body. In doing so it often becomes more concentrated and powerful than the Man-o’-War’s sting.
Beware toxic time bombs
Nudibranchs can be just as hazardous dead as alive. Always treat them with respect if you find one in your tank and never touch one without gloves and/or tongs. Even a dead slug can give a powerful sting.
Quick Q and A
Can nudibranchs see?
Nudibranchs, like their gastropod ilk, only have the most rudimentary eyesight. At best they can make out the difference between light and dark, which regulates their rhythm between day and night.
They have no colour perception and their bright markings play no role in identifying mates or rivals. Instead, they rely on smells and tastes, detected by their rhinophores and cephalic tentacles respectively.
How do you sex nudibranchs?
Simply! All nudibranchs are simultaneous hermaphrodites, meaning they have both male and female reproductive organs. Every nudibranch carries eggs and sperm, and it’s down to finding another nudibranch of the same species before breeding can start.
How big are they?
Most are rather small, with most adults seemingly under 10cm/4” in total length. However, there are some absolute brutes out there. The Spanish dancer, the famous swimming nudibranch, has been reported at over 50cm/20”. The sad fact remains, however, that if you find a nudibranch that has somehow sneaked into your aquaria then it will be unlikely to see out the month before starvation takes its toll — let alone reach adult size.
Are Berghia very effective in Aiptasia control?
Hell, yes! Berghia nudibranch are ravenous predators in an aquarium, but otherwise reef friendly. You’ll likely not see them on the job until they’re almost out of food, as they prefer to do their feeding at night and are shy of aquarium lighting.
If you see them looking during the day it’s a pretty clear indication that the little fellows are near starving. They can get into all the nooks and crannies you’ll not be able to physically reach, as well as hunt down those Aiptasia that you can’t even see.
Try to bear in mind that young Berghia are surprisingly delicate and will struggle to acclimatise if purchased too small. As a guideline, you want to be looking at buying them at no less than 12mm/0.5” if you want successful introductions.
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What scientific reactions are taking place in our reef tanks? Levi Major unravels some chemical mysteries.
How does calcium carbonate form in my tank?
This is created in the aquarium by two main processes. Firstly, calcium and carbonate ions can be locked by living organisms, such as coral or coralline algae, within their calcium carbonate skeletons. Non-biological (abiotic) precipitation can also tend to occur.
For either to take place there’s a requirement for both calcium and carbonate ions to be in solution generally at or above the solution point.
This can be taken as the point where the rate at which calcium and carbonate ions in solution land on a solid calcium carbonate surface and come out of solution is equalled by the rate at which they leave to become part of the solution.
If we raised the levels of calcium and/or carbonate within the solution it would be supersaturated — having more ions in solution than can be deemed stable over a long term.
Then precipitation of calcium carbonate can take place because the rate at which ions land on the surface of the solid exceeds the rate at which they can leave. Therefore, the solid surface is built up with further calcium and carbonate ions.
Even though more complex than abiotic precipitation, corals almost exclusively take calcium and carbonate ions from the solution to deposit their skeletons. The chemical composition of calcium carbonate (CaCO3-Ca2+ + CO3-2) indicates these organisms use a 1:1 ratio of calcium and alkalinity.
However, the consumption of calcium can be seen to vary from species to species, due to the incorporation of magnesium within calcium carbonate.
If we discover that we have very high calcium or alkalinity in our aquaria, precipitation of calcium carbonate can reduce the level of both in solution.
If we increase the levels of these ions so that they exceed the saturation point then the rate of calcium carbonate precipitation is increased. The result is accelerated coral growth.
Conversely, if the levels of calcium and/or carbonate ions in solution were below saturation point there would be no net gain in precipitation of calcium carbonate.
So should I just maintain high levels of calcium and alkalinity if I want fast coral growth?
Not exactly! The actual rate at which calcium carbonate is deposited can be affected by certain other water parameters, such as pH and magnesium.
Both bicarbonate and carbonate are forms of the same ion. At a lower pH, the bicarbonate form (HCO3-) predominates, whereas at a higher pH more of the carbonate form (CO32-) exists.
The effect of varying pH can be acute, in that each drop of 0.3 pH units below a pH of 9 causes a two-fold drop in carbonate concentration.
A full pH unit drop would correspond to a ten-fold decrease in carbonate concentration.
Accordingly, by varying the pH of a solution we can also change the amount of carbonate ion in solution. As mentioned, the concentration of these ions in solution determines the rate at which carbonate ions land on the surface of the solid. So the higher the pH, the faster the rate at which these ions land. Therefore the solubility of calcium is lower at higher pHs.
Lower solubility implies that as pH increases the amount of calcium and alkalinity that can be kept in solution without precipitation occurring decreases.
If we were to add kalkwasser (limewater) solution to the aquarium, pH would increase. This would rapidly permit precipitation of calcium carbonate.
This is not necessarily as a result of increasing levels of calcium or alkalinity, but also due to the fact that as we increase pH much existing bicarbonate within the water converts to carbonate. Then there’s a resultant spike in carbonate concentration.
The opposite is true with a falling pH in that the amount of calcium and alkalinity that can be kept in solution without precipitation occurring increases. This is why adding carbon dioxide to a reactor dissolves the media.
You may think a lower pH is better as you can maintain calcium and alkalinity levels better and abiotic precipitation of calcium carbonate will not occur. However, your corals would have to work harder converting bicarbonate to carbonate to allow calcification.
How does the level of magnesium affect the levels of calcium and carbonate ions in solution? Does it affect the rate of calcium carbonate precipitation?
The role of magnesium is far more complex than pH and alkalinity. If we examine standard seawater magnesium is the third most abundant ion after chloride and sodium, so its presence complicates our simplistic view of calcium and carbonate ions landing on and leaving the surface of our solid calcium carbonate.
Magnesium ions can be incorporated into the crystal structure of calcium carbonate and replace the role of the calcium ions.
As ever more magnesium is incorporated onto the surface of the calcium carbonate a layer of calcium and magnesium carbonate is formed. This results in the surface of the calcium carbonate no longer resembling one of calcium carbonate, preventing a firm bond of further calcium and carbonate ions. Further precipitation of calcium carbonate is largely reduced.
The extent to which magnesium is incorporated within calcium carbonate surfaces depends on the amount of ions in solution. The greater, the more it is incorporated.
If magnesium levels are lower than normal, it may not adequately get onto the growing calcium carbonate surfaces. This will then allow calcium carbonate to proceed even faster and may lead to increasing abiotic precipitation of the calcium carbonate.
Our inability to maintain adequate calcium and alkalinity levels, despite extensive supplementation or evidence of abiotic precipitation of calcium carbonate on heaters and pumps, means that the levels of magnesium are inadequate within the home aquarium.
Should I use supplements if my parameters seem fine?
Routine water tests will show your parameters and whether you need to supplement your tank beyond a water change. If you know what parameter is out of kilter, you should now know the best way to tinker and tune your set-up.
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Looking for the next challenge? Can we make a success of azooxanthellate coral tanks? Jeremy Gay suggests making a bold move with a future marine project.
We can do soft, LPS and even SPS corals with ease these days, so where is the next challenge for the enterprising reefer? The answer is non-photosynthetic corals.
These include more common species like Sun corals (Tubastrea spp.) but also the brightly coloured and considered near impossible Dendronephthya and Scleronephthya, and the gorgonians such as Acabaria, Acalcygorgia, Melithaea and Subergorgia.
You could be the best SPS coral propagator in the world, yet success with these creatures is far from guaranteed. With non-photosynthetic or azooxanthellate corals it isn’t about light, as you might expect. Instead it’s to do with the right type of water flow, delivered the right way over a 24-hour period, and feeding.
Divers and naturalists are aware that gorgonians, or sea fans as they are also known, are usually found at depth, projecting at right angles from rock walls where their branch-like structures collect food particles from passing currents. The flow is known as laminar, moving uni-directionally, and the corals position themselves to expose maximum surface area to catch food. In strongly tidal zones the flow will also reverse over a 12-hour period.
This leaves the reefkeeper facing a most interesting conundrum, as most of us have just spent the last 15 years equipping our aquariums to replicate the brightly lit reef crest where photosynthetic corals grow in chaotic and ever changing flow conditions.
A complete rethink will be necessary to provide the right flow conditions for these plankton-eating corals and, 99 times out of 100, a completely separate tank set-up too.
Flow must be uni-directional, and not too hard you may think, but that flow must also be capable of keeping the plankton in the water column for as long as possible to give the corals the best chances of capturing them.
Say goodbye to any mechanical filtration, as this will remove the precious food source. Initial trials, placing gorgonians in a tube as part of a closed loop, showed promise, although it will not look anything less than a science experiment if you choose to display them that way in your home.
A separate sump-style arrangement with baffles arranged in a similar way to an algal refugium may work, or even the 'manifold' pump and pipework arrangement used by many freshwater loach keepers.
Replace the sponge strainers with more open plastic ones and your plankton may recirculate many times, offering excellent capture possibilities.
Install ball valves in recirc pipework or inline taps into manifolds so that you can control that flow too.
Just to make things more complicated, it’s also about tethering that flow so the polyps can open to their maximum and create an eddy that moves prey towards them. Too much flow and they can’t open or function properly. Much experimentation is needed and, to make things worse, preferred flow velocity varies from species to species!
Zooxanthellate corals derive some energy from the symbiotic zooxanthellae algae that live within their tissues, so secondary feeding of other foods like phytoplankton or zooplankton isn’t as critical as with the gorgonians, and heavy feeding of zooplankton, although benefiting many light-loving corals and other organisms, can add to the biological load and nutrient poor environment we are wanting to create.
Azooxanthellate corals rely totally on food capture for their nutritional needs so — like fish — no food, wrong food or improper diet will end in death.
It was thought that zooplankton was the main requirement for azooxanthellate corals, though smaller phytoplankton are now also believed necessary, along with many other foods like bacteria and nutrients like amino acids.
Luckily they are available, so how much food do we offer and how often?
Provide suitable foods in terms of nutritional content and capture size as and when you can. Some public aquariums even pump in natural seawater 24/7 to try to get adequate results.
A quick Internet search reveals mixed results if considering keeping what many deem impossible. Don’t bother as azooxanthellate coral tanks are too hard, say many industry experts and scientific peers — yet search on and you’ll find photographic evidence of a growing number not only working but appearing to thrive.
That leaves another conundrum: whether to invest time and resources in giving it a go and risking failure, or simply leaving well alone. No one wants dead corals and that is a huge strain on the world’s resources in terms of collection, shipping, transport, packing and energy, but without someone prepared to give it a go we wouldn’t be where we are now with SPS corals!
This item first appeared in the June 2010 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.
Complicated life cycles ultimately create these simple but beautiful sea creatures. David Wolfenden wonders if jellyfish are about to become a home hobby favourite.
Every now and then, a fair number of hobbyists become interested in keeping jellyfish at home. However, this idea is never sustained and jellies have failed to become as popular as predicted.
They remain, however, a relatively common sight in public aquaria and, with some commercially available systems now appearing, how viable do they now seem for domestic tanks?
Keeping jellyfish is a relatively new branch of aquarium science. Until recently it was thought impossible to keep pelagic (open ocean) jellyfish for any length of time in captivity — standard aquarium conditions proving totally unsuitable.
However, pioneering work in the early 1990s at California’s Monterey Bay Aquarium, along with data gathered in Japanese aquariums, succeeded in maintaining a variety of species, starting with the Moon jelly (Aurelia aurita) which is still the most common jellyfish in captivity.
Success with keeping jellies was due to the development of the kreisel tank (from the German for ‘merry-go-round’), which was originally designed to keep gelatinous planktonic animals alive on research ships and in laboratories. The aim is to produce a gentle, flowing water motion in which the delicate jellies and their food can be suspended.
Many aquarium jelly tanks are more correctly referred to as pseudokreisels as they 'borrow' elements from the 'true' kreisel design but modified for better viewing.
Simple, but complicated
Aurelia aurita is a species of scyphozoan ('true') jellyfish with a more or less worldwide distribution. There is debate about the taxonomy of the genus Aurelia, but we consider it a pretty cosmopolitan group of closely-related populations.
The familiar 'jellyfish' (the 'medusa' stage) is only a part of the life cycle of Aurelia, which is seemingly rather complex for such primitive, simple creatures. Adult medusae reproduce sexually to produce a planula larva which anchors itself to a substrate before becoming an anemone-like scyphistoma —the polyp stage – similar to those of corals, to which jellyfish are related.
This eventually becomes a strobila — each one producing around 15 flattened discs and each of these being an ephyra, a juvenile jellyfish with a star-like appearance and eight bifid ('split') arms released in a process called strobilation. The ephyrae become part of the plankton where they grow into medusae — the reproductive and dispersal stage — and the life cycle turns full circle. Life spans of over four years for individual Aurelia medusae have been reported, although two is a more usual.
Polyps can be maintained simply in a small, bare aquarium with open-ended air line fixed to the base to circulate food — Artemia nauplii, preferably decapsulated to prevent ingestion of the indigestible cysts — and provide gas exchange. Filtration is unnecessary, with water quality maintained through regular syphoning of detritus and subsequent water changes.
Ensure that excessive feeding doesn’t allow hydroids to take over the tank. If maintained at a constant temperature and fed sufficiently, the polyps will reproduce asexually by 'budding' so a small number can give rise to a carpet. Add shells and other objects to which they can attach.
Strobilation in Aurelia occurs after prolonged changes in temperature and some success has been achieved by adding iodine to the culture water, although different ‘strains’ of Aurelia may have different triggers for strobilation.
The resulting ephyrae should be removed from the polyp tank to prevent them being eaten by the polyps and transferred to a similar set-up, the open-ended air line helping to move the juveniles and keep the Artemia in suspension.
This can work well as a 'grow out tank' until the ephyrae have become recognisable as small medusae up to about 2cm/0.8” across — by which time they will need to be transferred to a kreisel tank as air bubbles can start to damage them.
The basic design for a jellyfish tank can be quite simple — although commercially-available systems are available, DIY kreisels can be made with a little ingenuity.
The illustration above shows a simple design for a basic pseudokreisel tank. This successfully housed Aurelia medusae. Filtration was not utilised, water quality being maintained with regular syphoning and water changes, although external biological filtration could be utilised via the rear ('non display') portion of the tank.
A jelly tank must be radically differently from a normal aquarium. A well-designed kreisel (or pseudokreisel) will create laminar, sheet-like water circulation patterns to keep the jellies in suspension. Flow rates must be gentle to prevent damaging them, but strong enough to keep the animals moving and prevent dead spots where they might collect.
Aeration is not a feature of such tanks, as any air bubbles will become stuck under the medusa’s umbrella, leading to holes in the body. If these aren’t removed rapidly the jellies will die and many a tank has suffered a wipe-out from accidental introduction of air bubbles.
Gas exchange will take place at the water’s surface, even in gentle flow, but ensure that a 'skin' of oil isn’t allowed to accumulate there.
Biological filtration is beneficial provided it can’t introduce air bubbles into the tank and a coarse medium, such as bio-balls, prevents the jellies’ food becoming rapidly depleted — media-like foam tending to filter the feed out too efficiently.
Some basic tank designs don’t employ filtration at all and these can be reasonably successful, although very frequent water changes are obviously necessary — which aren’t a problem for most public aquariums but less practical at home. Protein skimmers are usually considered unnecessary for jellyfish kreisels, as they may clean the water a little too aggressively, not to mention increasing the risk of potentially lethal microbubbles being added to the tank water.
Aurelia are temperate and chilling the water may be another requirement: the optimum range for most strains being 10-15°C/50-59°F, although slightly higher temperatures are often tolerated.
Large medusae will benefit from varied feeding — in addition to decapsulated, preferably enriched Artemia, there’s room for a certain amount of experimentation. The Monterey Bay Aquarium include Pacific krill in the diet of their Aurelia, and Japan’s Osaka Ring of Fire Aquarium report that minced clam as a supplementary feed prevents deformation and promotes healthy growth. Aim for variety in the medusa diet.
Aurelia doesn’t have special lighting requirements, but actinic blue lighting is aesthetically effective, as well as reducing algal growth, so considerably cutting down kreisel maintenance.
If adult Aurelia can be kept for long enough in a kreisel, sexual reproduction may well happen, with polyps appearing in the tank as a result. These can be scraped off the glass with a razor blade and transferred to a culture vessel, although another way is to place half scallop shells on the kreisel’s base. They are flat and smooth enough for the medusae to glide over them, but are an ideal substrate for settlement by the planula larvae. Once a few polyps are on the shell, they can be easily removed and cultured separately.
Catch your own!
Where can you get jellies? You can’t pop down to your local shop to buy Aurelia, which leaves one option – catch your own!
A little bit of 'pioneer mentality' is required if you’re serious about jellies! If able to obtain wild Moon jellies, they are best transported in large, thick plastic bags with all the air squeezed out — and never take a jelly out of the water!
A few polyps are all that’s needed for a starter culture. Using wild-caught animals may not initially be ideal, but our knowledge of their reproductive habits and culture requirements is now sufficient to allow a genuinely sustainable captive population of jellies to quickly become established from a few wild-caught individuals. After all, this is what public aquariums have been doing for years, with by far the vast majority of specimens on display being captive-raised.
Other, more ‘exotic’ species of pelagic jelly are successfully maintained in public aquaria and all present unique challenges. One such beautiful species is the Pacific Mastigias papua, which houses symbiotic zooxanthellae, as does Phyllorhiza punctata, so these have additional lighting requirements.
Chrysaora fuscescens, the sea nettle, is also kept by some establishments, but these are large and generally require supplementary feeding on other jellyfish! Whether any of these could be viable for home culture is debatable…
Easier to maintain in captivity are the 'upside-down' jellies of the genus Cassiopeia, which are occasionally seen in the trade. Unlike Aurelia or other pelagic jellyfish, this species spend most time on the shallow sea floor, upside down to expose their symbiotic zooxanthellae to the sunlight.
Adults of C. xamachana can grow to a diameter of 30cm/12”, with a lifespan of around one year, with the more commonly-available C. andromeda reaching 20cm/8”.
Ethusa spp., a group of crabs, are regularly seen on Indo-pacific reefs carrying Cassiopeia jellies on their backs for camouflage and protection. While not as mesmerising as their pelagic counterparts, these can look stunning, often exhibiting delicate blue and purple coloration.
Care for Cassiopeia is more straightforward than for say Aurelia, or any other truly pelagic jelly, although specific requirements still need to be catered for. They can be kept in shallow aquaria —depth being less important than area — with a sandy to coarse substrate, and they do best in a species tank. Many specimens are doomed to die quickly as ‘novelty’ additions to a standard reef aquarium.
Filtration can be achieved via the reverse-flow method, although many public aquaria do not utilise biological filtration to achieve rapid growth rates. Cassiopeia are hardy and tolerant of a range of water quality parameters and detectable levels of ammonia don’t seem an issue. In fact, ammonia supplies the jellies’ algal symbionts with nutrients, resulting in greater growth rates than when biological filtration is employed!
Some aquarists also report that reproduction is triggered by increases in ammonia. It’s vital that Cassiopeia receive intense lighting of suitable ‘reef’ quality, but won’t tolerate currents normally associated with reef aquaria — so strong or even moderate water movement is a no-no!
Feeding on Artemia nauplii —again, preferably decapsulated — and other foods is necessary.
Breeding Cassiopeia in captivity is possible and many public aquariums culture upside-down jellies as a food source for other species. Cassiopeia polyps continuously strobilate at temperatures above 25°C/77°F and polyps kept in a culture tank at a lower temperature will asexually bud off tiny replicates of themselves, so it’s possible to keep a healthy supply of polyps.
Ephyrae and small medusae can be maintained in simple 'grow-out' tanks.
This item first appeared in the November 2008 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.
Not only are some marine inverts difficult to keep, some can be downright dangerous! Scott W. Michael lists a few that should remain in the oceans.
The sea slugs, the nudibranchs for example, come in a myriad of chromatic hues. Yet while you may be tempted to add one to your nano reef tank, I would discourage you.
Many are naturally short-lived, some living less than a year in the wild. Most have specialised diets that include sessile invertebrates, like sponges, hydroids, bryozoans and tunicates. Unless able to provide these food sources in the aquarium, these creatures will live an even more abbreviated life.
Also beware that there are species in at least one genus (Phyllidia - pictured above) that exude a fish-killing toxin.
The soft corals in the genera Dendronephthya and Scleronephthya (family Nephtheidae) which are usually referred to in the aquarium trade as Strawberry, Cauliflower or Tree corals, are some of the most striking corals on the Indo-Pacific reefs.
They tend to occur under overhangs or in caves, always in habitats exposed to strong pulses of current.
While coveted by reef aquarists, their special dietary requirements have thwarted attempts to keep them by all but the most dedicated. Their preferred food is phytoplankton.
In reef tanks they typically remain flaccid, as they do in the wild when currents are not flowing, and rarely live for more than a month or two.
Feather star (crinoids)
The crinoids, or Feather stars, are the Dendronephthya of the echinoderm world. They would make striking display organisms but their specialised diets hamper success in the home aquarium.
Their general feeding strategy consists of capturing and transferring tiny plankton, such as phytoplankton, invertebrate larvae and detrital particulates through ciliated channels in their arms to their mouth.
What makes matters worse in the aquarium, their arms often drop off due to stress or mechanical damage incurred during collecting and shipping. When losing an arm they lose part of their feeding 'machinery' — making it even more difficult to get enough nutrients.
Venomous sea urchin
The flower urchins (Toxopneustes sp.) are lovely echinoderms that have a large, tulip-like structure on a long stalk, known as pedicellariae.
Associated with this structure is a venom gland. If a person makes contact with the pedicellariae it can clamp shut like jaws and inject venom. The result is terrible pain and possible death.
While fairly well behaved as far as invertebrate tank mates are concerned, the potential for a dangerous 'sting' is not worth the risk. They often hide among rockwork and so accidental contact when working in the tank is highly likely!
The other venomous urchins to be avoided belong to the genus Astheonosoma and called Fire urchins because of the pain that results from their sting. These animals often exhibit beautiful colours and host various small commensal shrimps.
Carpet sea anemone
Many want to set up the amazing symbiotic association that occurs between sea anemones and clownfish in our aquariums. However, not all of the host anemones do well in captivity.
The carpet sea anemones (Stichodactyla spp.) should be avoided by most hobbyists. Those that available are often colourful and usually bigger than a dinner plate. Most carpet anemones will ship poorly and tend not to acclimatise to the home aquarium.
Large hermit crab
While bulletproof, the large hermit crabs in the genus Dardanus are as welcome in the reef aquarium as a two-year-old in a china shop! They are destructive!
The Dardanus are opportunistic feeders and usually large enough to tear up a variety of tank mates. This can include soft corals, large-polyped stony (LPS) corals, echinoderms and even sleeping fish.
These crabs will also knock over unsecure pieces of rock or coral colonies. This often occurs at night when they are usually most active.
Many sponges that are available to hobbyists do poorly in captivity. Most are filter feeders that will extract tiny plankton and bacterial aggregates from the surrounding water column. They feed most of the time and are unlikely to get enough to eat in the home aquarium, even if particulate foods of the right size are occasionally introduced.
Another potential sponge killer is exposure to the air, which can be lethal if air bubbles get trapped in the many tiny channels that permeate their bodies.
You see these less frequently in the trade nowadays and they have no place in the home aquarium. The blue-ringed octopus species most often encountered by aquarists is Hapalochlaena lunulata.
Blue-rings should not be imported because they are difficult to keep, but because they are deadly! They are responsible for the deaths of several humans and it has been reported that just one has enough venom to kill 26 adults. So, why take the risk and keep one of these virulent little cephalopods in your home aquarium?
See news story Octopus hospitalises 85 people.
Most sea cucumbers are cryptic, hiding under the sand or live under rocks and rubble. But the sea apples (genus Pseudocolochirus spp.) are conspicuous, colourful sea cucumbers that many reef aquarists adore.
However, they produce toxic compounds (holothurin) and, if they die, may exude this into the aquarium and quickly kill fish tank mates. It may also kill some invertebrates.
Sea apples also tend to starve to death, unless you make a concerted effort to target feed them foods for suspension feeders — for example, liquid or dried phytoplankton daily.
This particular echinoderm (Ophiarachna incrassata) is easy to keep and can be a welcome resident. However, it is a proficient predator that will eat fish tank mates and in time will usually capture goby neighbours.
This animal employs a unique ambush feeding strategy. It will lift its disc above the bottom and remain motionless. When a small fish swims under, possibly seeking shelter, it will quickly turn its body, so its legs are twisted in a spiral and imprison the fish. This is then easily consumed by the crafty echinoderm.
That said, it does have a place in an aquarium with larger fish.
This item first appeared in the June 2009 issue of Practical Fishkeeping. It may not be reproduced without written permission.
Pulsing Xenia makes a great addition to the reef tank, and it's a marvel to watch says Jeremy Gay.
Common name: Pulsing xenia.
Scientific name: Xenia elongata.
Origin: Indo Pacific.
Requirements: Moderate to bright lighting from T5, LED or metal halide. It should have moderate flow with ten times tank volume turnover per hour.
Water parameters: Very hardy with regard to parameters and tolerates even nitrate-laden water. (See notes below.)
Notes: Pulsing Xenia is the perfect soft coral for beginners as it tolerates and even thrives in less than perfect conditions.
Some reefkeepers say that this coral actually uses nitrates as a nutrient — and it has even been used in Xenia-only refugiums as it can filter water-removing nitrate and capture tiny food particles as it goes along.
The pulsing action of the large polyps on this coral are the main attraction!
You have to see a live one in action just to appreciate the marvel of this coral opening and closing all its polyps in quick succession, and it always grabs the attention of non-fishkeeping onlookers too.
It pulses to draw oxygen over itself and the less water flow it receives the more it pulses.
However, this coral is considered a pest by some marine keepers, as it can rapidly spread all over the aquarium. However, shops will always take any frags as imported specimens don’t appear to do as well — due to lack of oxygen available in transport.
Availability: Widely available from marine stores and hobbyists.
Price: £30-50, though frags will be £10 or even free from hobbyists.
Mantis shrimps can be the stuff of either dreams or nightmares, depending on your point of view. John Clipperton looks at the spearers and smashers.
Few creatures can inspire both awe and dread in equal measure among reefkeepers than mantis shrimps. However, these incredibly interesting creatures deserve our respect and are remarkable for so many reasons.
As marine crustaceans of the Stomatopoda order they are neither shrimp nor directly related to terrestrial ‘preying’ mantids. With over 500 species in this order described some have reached well over 30cm/12” in length. However, the behaviour of even large specimens is little understood.
Their cryptic, aggressive and often solitary habits are doubtlessly the reason, as they are widespread and numerous in many shallow water marine habitats, both tropical and temperate.
Spending much time hiding in rocky areas or lurking in burrow complexes in the sea floor, they ambush or even co-operatively hunt and kill living prey. Some species have taken on the venomous blue-ringed octopus as this is a spicy treat if suitably immobilised!
Depending on species, they can be diurnal, nocturnal or crepuscular and, based on anatomy and hunting behaviour, can be classified as either ‘spearers’ or ‘smashers’.
Many species live in shallows of tropical seas and we are most likely to encounter some of these either in shops or as hitchers on live rock.
Occupying such niches, mantids have become the ultimate assassins of their world and have a deadly array of weaponry based on the development of their raptorial claw.
'Spearers' have rapier-like appendages often with barbed tips or serrated edges which impale or clasp and disembowel prey. Such species are typically ambush predators that lurk in burrows made in soft substrates and feed on soft-bodied prey, including fish.
'Smashers' exhibit more club-like claws, which can still have sharp edges for cutting. After tackling prey in the open, the shrimps use these to pummel and dismember hard-shelled food like crabs.
Regardless of the equipment, the force and speed of strike movement is perhaps what makes this 'smash' weaponry even more impressive.
Due to a saddle-shaped 'click-joint' structure, a mantis is able to ‘cock’ its raptorial limb. Driven by powerful extensor muscles, much potential energy in the upper part of the limb can be created before and release during a strike.
The strike of some species is one of the fastest movements in the animal kingdom, with acceleration rates equivalent to the firing of a .22 calibre bullet.
Cavitation bubbles between the appendage and striking surface are produced and the collapse of these bubbles produces additional forces on the prey, resulting in a phenomenon known as sonoluminescence whereby a tiny amount of light and temperatures of several thousand degrees Kelvin are produced within the collapsing bubble. Pistol shrimps produce this effect in a similar manner.
Such weapons aren’t much use without a targeting system to match and stomatopods have the most sophisticated visual system of all animals.
Each compound eye is made up of up to 10,000 separate lenses. A central region (midband) divides the eye into three, enabling the mantis shrimp to see objects with all three different parts of the same eye. So basically, trinocular vision and depth perception are possible in each eye!
The areas above and below the midband of each eye are used for recognition of forms and motion but not colour vision. However, the midband of a mantis can contain up to 16 types of photoreceptors, with 12 for colour analysis alone.
As a result, stomatopods can see polarised light, four colours of UV light and may also be able to distinguish up to 100,000 colours — that’s ten times the range of human beings. Backing up this 'hyperspectral' vision, groupings of special muscles allow the eyes to move independently across a wide field of view. This allows the mantis to build a detailed picture of its surroundings and efficiently identify and track predators and prey.
This visual system is also known to play a key role in a range of mantis behaviours; from conflict avoidance to courtship. Some species use fluorescence to signal in deep water.
Thanks in part to these skills and survivability, small ‘smasher’ specimens occasionally survive transit and hitch into aquaria in pieces of live rock. Their presence can often be established by sounds of their activities, as well as visual confirmation. To view species that hitch into tanks, using a red torch at night may offer the best chance.
Relatively harmless pistol shrimps can often be mistaken for stomatopods as they make a similar noise. They make an occasional single 'snap' while a 'smasher' mantis attack will normally be heard as a rapid series of thuds!
If a mantis is found in a tank, rather than viewing it as a disaster think positive. It may be an unusual or even undescribed species!
Live rock first
However, to try to avoid such a situation when setting up a new reef tank, allow a couple of weeks with only live rock in the tank.
This not only identifies organisms that may need removal, but also enables the tank to cycle properly. Catching such creatures with a trap, or by removing rockwork for a low salinity dip, may be necessary and requires patience, skill and luck! Having just rock in the tank makes either method far easier.
Once caught, if the creature cannot be ‘sumped’, consider asking if a local store will take it. However, mantis shrimp often sell quickly on reef-related Internet forums. They can make fascinating subjects — but large ‘smasher’ species can break even thick aquarium glass!
If setting up specifically for a mantis, depending on the species, there are things to do to optimise the system.
After considering construction and size of tank, include the right kind and depth of substrate for the species in question as they need to go burrowing.
High light intensity is not necessary. Instead efficient filtration should be paramount and designed to deal with messy feeding, stirred-up substrate particles and a high organic loading.
Tank mates can be included with certain species of mantis shrimp if sufficiently robust, but generally mantids are better housed alone.
It goes without saying that you should be extremely careful when performing tank maintenance and ensure the tank is securely covered to prevent escape. You wouldn’t want to find one of these in your slippers!
Some striking mantis shrimps you might like to consider include:
Perhaps the most well known stomatopod, the Peacock or Harlequin mantis is the largest ‘smasher’ reaching around 20cm/8”.
From sandy, gravel bottoms often near reefs and in depths of up to 40m/131’, this species constructs a robust U-shaped burrow and preys on snails, crustaceans and bivalves.
Its common name arises from the flamboyant colour of the tail (telson).
Provide a minimum 100 l/22 gal tank capable of withstanding heavy impacts and furnish with a deep mixed substrate and rockwork — which will be extensively rearranged!
The Zebra/Striped mantis is the largest stomatopod, reaching to around 40cm/16”. This ‘spearer’ deserves extreme respect, with adults possessing ‘spring-loaded’ bayonets several centimetres long to impale soft-bodied prey.
They inhabit burrows made in muddy or sandy reef flats in waters up to 10m/33’ deep. Provide a tank of at least 120 l/26 gal volume with a deep fine/mixed grade substrate.
Reaching a modest 10cm/4” the Rainbow mantis makes an interesting addition for a small tank and, being a ‘spearer’, presents little risk of structurally damaging a tank.
Various colour forms have been noted, ranging from black with white markings to solid orange, and they can even change colour on moulting based on their surroundings. Furnish the tank with a few inches of sand, rubble and live rock and feed with fish and crustacean flesh every few days.
Another ‘smasher’, the Purple-spotted mantis gets its name from markings on each merus (upper part of secondary maxilliped). A typical pose is known as the ‘meral spread’ which is commonly used in this species to avoid any direct conflict.
Attaining a maximum size of around 10cm/4” this species doesn’t require a large tank, but still needs a suitably deep substrate and rockwork.
In the wild they will often forage for crustaceans and snails in shallow water and this makes for an interesting and active species in captivity.
This article was first published in the August 2009 issue of Paractical Fishkeeping magazine. It may not be reproduced without written permission.
Also known as Monti for short, Montipora capricornis is a widely available coral, but try to buy frags if you can, says Jeremy Gay.
Common name: Montipora, Monti
Scientific name: Montipora capricornis
Origin: Pacific Ocean
Requirements: Bright lighting from metal halide, multiple T5 or high power LEDs. Strong flow averaging 20 times tank volume turned over per hour.
Water parameters: 24-26°C/75-79°F, sg 1.026, 35 ppt. pH 8-8.4, alkalinity 7-9 KH, calcium 400 ppm, magnesium 1350 ppm. Phosphate and nitrate zero.
Notes: One of the easiest SPS corals to recognise, the orange Montipora capricornis is also one of the easiest to keep. Its plate-like shape and swirls and its bright colour make this a popular addition to reef tanks. It is also a good stepping stone coral if on the way to trying out a full-blown SPS system with more demanding species like Acropora.
In the right conditions it has high calcium demands, so lots of water changes with a good salt, supplements or automated dosing may be necessary. If left unchecked it will form a large plate, 30cm/12” plus in diameter and then start to grow vertically too, taking on its characteristic and desirable swirls.
Its size and shape will mean it will shade corals beneath so place low down in the aquascape, lighting permitting. However, the overhang it creates does look characteristic of a natural reef.
This species is easy to propagate in reef tanks – sometimes by accident as its brittle skeleton makes it vulnerable to breakage. Broken-off bits and frags will continue to grow unaffected, making it also suitable as a fragger’s first SPS coral.
Availability: Widely available from marine shops and mail order coral websites. Fragged and captive cultured specimens are better in terms of acclimatisation and in protecting the reefs from overcollecting.
Price: £30-50, depending on size. Frags may be as cheap as £10.
This item was first published in the December 2009 issue of Practical Fishkeeping magazine. It may not be reproduced without written permission.