To avoid becoming a squishy heap on the ground humans have a skeleton. Quite a good invention really, not having a skeleton would cause quite a few difficult problems.

Humans aren’t alone with the possession of a skeleton of course; there are all sorts of life forms that have one too, how about the elephant or man’s best friend the dog as just two examples.

Skeletons are not essential to life however; there are creatures that don’t use one at all. As a non-scientist I can say that they use a different method to maintain their body shape, I’m not sure how a scientist would put it. For example a shrimp has a hard outer shell rather than an inner skeleton.

Vertebrates, those that have a skeleton, are vastly outnumbered in the world. It is estimated that vertebrates are around 3% of the life forms in the world. It follows that a massive 97% (I just had to demonstrate my mathematical abilities) are invertebrates.

There are land dwelling insects such as spiders and worms, examples of well known invertebrates. In the cold sea there are huge numbers of plankton, anemones, sponges etc. The warm seas contain many better known (to the marine aquarist) invertebrate species, including filter feeding worms, shrimps, corals and sometimes very large anemones. It is with some anemones of course that the representatives of the vertebrate/invertebrate world have combined forces to mutual advantage; these are the clown fish with their selected hosts. There are other examples of this life style.

Invertebrates are very adaptable as demonstrated by the discovery of volcanic activity deep in the sea well beyond the sun’s light. Scientists used to accept that life basically depends on the availability of light from the sun, an example of which is that plant life uses the sun’s light to photosynthesize and grow, and then the plant life is eaten by a herbivore from which energy is obtained. Herbivores are then the prey for carnivores. They all basically depend on the plants and the sun. This belief has been changed by the life found near this deep volcanic activity, including filter feeding worms, mollusks, bacteria and crabs which depend not on the sun’s light but on heat and chemicals.*

Anyway marine aquarists, or rather those who maintain a reef system, keep various types of invertebrate including shrimps, corals, sponges, anemones, filter feeding worms etc. These very interesting life forms only ask for a few things for success, including high quality seawater, for the majority of corals and some others sufficient light of the correct spectrum, space to grow and freedom from predation. It is usually important to place for example corals in a position where they receive sufficient seawater flow.

It is worthwhile noting that all marine aquariums, big or small, fish only or reef, depend on invertebrates for their health and life. The bio-filtration system, whether this is live rock or canister filters, contains bacteria that deal with the toxins ammonia and nitrite. Without these bacteria the life in the aquarium would die. With live rock, further bacteria should be able to deal with the sometimes troublesome nitrate.

Those aquarists who make use of natural live rock could discover that they have invertebrate life forms in their aquariums that they didn’t import themselves or at least not intentionally. Some such as filter feeding worms could be welcome. Others such as the Aiptasia anemone are not welcome. The Mantis shrimp is another, though in this case it is worth keeping but needs re-housing to an area where problems won’t arise.

Invertebrates provide the aquarist with a chance to create a living reef at home, be this large or small, though compared to Mother Nature’s creations all home reefs are miniscule. Nevertheless, a successful home reef is wonderful to see.

(* Reference: Marine Invertebrates. Martyn Haywood & Sue Wells)

Most marine aquarists are only too happy to have something different in their aquariums, as long as that something fits in with the current population.

The apple being talked of here is the Sea Apple which is definitely different! As can be seen it’s colourful too. An aquarist who has one will usually be fascinated by ‘the thing in the corner’. The Sea Apple has been available to aquarists for many years. I feel that the beginner aquarist should let experience build before keeping one, as a pure guess say about a year, or at least until the common general husbandry mistakes are no longer made and seawater quality is consistently high. This is important as will be seen.

‘Sea Apple’ is the common name; the proper one is Pseudocolochirus axiologus. They need the usual correct introduction to the aquarium, that is, acclimatization, and should not be exposed to air. They need to be handled gently but this of course is the same for all livestock.

The Sea Apple does not require reef lighting as it is not a coral but a species of sea cucumber. This can of course be confusing, the common name talks of ‘apple’ yet the species is ‘cucumber’. (This seems to happen from time to time, such as the Foxface fish (Lo vulpinus) that belongs to the rabbitfish family.) The Sea Apple is usually able to grow to about 4″ (circa 10cm) though there are larger species that grow to about 6″ (circa 15.25cm) or more though these are not so readily available and are more expensive.

The Sea Apple is able to move slowly around the aquarium and will do so until it is happy with its position, and this depends a lot on seawater flow. The flow doesn’t need to be very strong but moderate to brisk. This is because from the top centre a crown of feathery tentacles will appear and too strong a flow could cause problems. As said, the Sea Apple will make its choice and the final place could be a viewing glass, a corner, a rock or even the tube from a tubeworm. The aquarist has his or her preference for position, so keep those fingers crossed. The final position is likely to be between half way and the top of the aquarium. Once the Sea Apple has come to rest it should be left in peace unless the position is causing trouble to other livestock or presents a danger to the Sea Apple itself. It should not be irritated by the aquarist; this could be a real problem as will be seen.

The tentacles are used for feeding and are extended into the seawater column for this purpose. Fine particulate matter is captured and, one by one, the tentacles are passed into the mouth for removal of any food and then withdrawn, it’s a bit like a human sucking food off the fingers. This is a fairly slow process and is fascinating to observe.

The Sea Apple is quite hardy in a high quality environment and can live a long time. Many do fail though and this is to do with feeding, or rather the lack of it. In most aquariums there is insufficient suitable fine particulate matter in the seawater and therefore the Sea Apple doesn’t get enough to eat. This causes it to slowly shrink until it dies. Target feeding is needed, the frequency of which is best twice a day or more if the need is observed. There are plenty of commercial fine foods available that are suitable. All that is needed is for this food to be squirted into the seawater with a suitable instrument a little upstream from the Sea Apple when it has the tentacles extended, the food will then drift over them. If the seawater current is too high causing the food to pass too quickly, turning off the pumps for a short period will not do any harm. Any of the fine food that is not taken will drift off and could well be captured by corals.

Overall I would suggest that a reef system is the best aquarium for the Sea Apple to be introduced into. The reason is that there is a greater likelihood that there will not be any fish present that could nip at the tentacles, though this is not always the case. If the Sea Apple is excessively harassed then serious trouble could occur.

The problem that a Sea Apple could cause is very serious. If it is excessively harassed and stressed a toxin could be released that could, and likely will, kill the other livestock. Not a pleasant thought. That is why the Sea Apple should not be harassed excessively by the aquarist and its tank mates should be suitable. In addition it would be a good cautionary measure to protect the intakes of circulation pumps etc so that the Sea Apple cannot be accidentally damaged, this should be done before introduction.

Having said that, the Sea Apple should be a good introduction to a suitable high quality environment provided the aquarist has reasonable experience and feeding is given suitable attention.

Quite apart from fish there are many varieties of life. As the systems in this case are reefs the next is corals, both hard and soft. The corals are really what make the display a reef, the rocks may be ‘live’ and there may be fish flitting about, but it is the corals that make the picture.

Seen less are sponges as these are considered difficult by many aquarists and therefore they are not always attempted. It is reported that many sponges are not as difficult to keep as imagined, but their demise is often because of poor collection when damage is caused or when the sponge is allowed to come into contact with air. Algae can be another sponge enemy.

A spectacular life form that could be kept in a reef aquarium is a worm. Not just a worm though, this one is a real show off. The worm lives in a tube and is considered very attractive because of the head of feathery tentacles that appear. They are expanded into the seawater in order to trap food. The expanded tentacles do look similar to the old fashioned dust mop or feather duster that tackled cobwebs etc in days of old.

The worm is understandably commonly called the feather duster worm, or sometimes the peacock worm. The proper name for arguably the best is Sabellastarte magnifica. Feather dusters are common in warm seas and are usually easily obtained from local fish shops.

The tube extends from the rubble or rocks but all of it is not usually in sight. The tube could be up to 6 inches in length and the extended tentacle crown could be between 2 and 3 inches in diameter. The worm slowly extends the tentacles often stopping during the process and if everything seems fine the tentacles are completely extended. As they fully emerge they open up into the distinctive head.

The worm doesn’t appreciate strong seawater currents because of the head. If the current is too strong the worm could withdraw back into the tube. It is best to locate the tube in an area where only slight to moderate currents exist.

If a worm is seen to be hanging listlessly out of the tube it is likely to be dying.

When the tube with the worm within is first introduced to the aquarium the proper acclimatization technique should be applied. During this period it is best to ensure the tube is not exposed to air at all. Once the worm is ready for transfer the tube can be placed securely between rocks being careful not to crush it, when the worm is active it should adjust any faulty anchorage. Place the worm as said in an area of light to moderate currents, and lower down on the reef particularly if the lighting is powerful. The worm hasn’t any need for lighting as corals have. A worm that is positioned in bright light could be slow to appear until it is accustomed to it. It is reported that the worms do not like high temperatures – a top temperature of 76 deg F is sometimes quoted, though I kept one at 77 deg F for a long time.

Sometimes an aquarist can be alarmed as the worm drops its crown of tentacles. This could have been caused by stress produced by too high a temperature, excessive and sudden seawater currents, too large a change in seawater specific gravity or harassment. The first three are easily avoided. Harassment is avoided by ensuring that only suitable tank mates are present. Many common reef fish, such as damsels, dwarf angels etc could nibble at the worm’s tentacles. There are more that could cause a problem. Fish such as the copper-band butterfly (Chelmon rostratus) should be avoided. The best fish to keep with the tubeworm are small dottybacks, fairy baslets, gobies, blennies and the like. The worm can disappear into its tube at a terrific speed thus avoiding trouble, but repeated occurrences of this lead to stress. Once any problem has been corrected leave the worm alone. It could take a longish period to re-appear, and they are capable of re-growing a crown.

The tube worm feeds on very small plankton in the wild. In the aquarium once the worm has been given time to settle and is displaying its full crown of tentacles it can be target fed. Using a small syringe-like device, a small amount of fine filter-feeder food can be ejected ‘upstream’ and allowed to drift over the tentacles. If necessary seawater movement pumps can be temporarily turned off though this should not be necessary. It is best not to squirt the food straight at the tentacles or it is likely the worm will withdraw them believing danger is present. In an aquarium where there are many other filter feeders the food shouldn’t go to waste and the seawater quality shouldn’t be affected.

Looking at the suggested fish companions for the worm it seems the ideal home would be a nano aquarium. In these small systems it is usual to keep smaller inoffensive fish. The worm can successfully be kept in a large system subject to the other inhabitants, which means a lot of discipline could need to be applied by the aquarist.

The feather duster worm is a different and very interesting addition to a captive reef. Below is a short video.

While in cautionary mode, it should be noted that anemones are not for novices, it is necessary that experience is gained first, experience in maintaining high quality seawater and equally high quality general habitat. In addition, anemones such as the one looked at here require correct lighting, in the same way that most commonly kept corals do. This is because of the presence of zooxanthellae, single celled symbiotic algae within the flesh. The zooxanthellae give the anemone its colours.

The Rose Anemone is properly called Entacmaea quadricolor. Looking at the proper name it is clear why it is also commonly known as the four coloured anemone. It can also be recognized as a short part of the tentacles are bulbous, this occurs towards the ends. Remembering that some clownfish refuse for some reason to take up home in an anemone even though it is of the correct type, the Rose Anemone should be acceptable to Amphiprion bicinctus, A. clarki, A. ephippium, and A. frenatus. That’s quite a choice, but as said there’s no guarantee.

Some symbiotic anemones will anchor themselves in the substrata which can sometimes present a positioning problem for the aquarist. The Rose Anemone however doesn’t require substrata, it is happy on rocks. Well, that isn’t completely correct, it is happy between rocks in a fairly deep cleft, which is best smooth, meaning smooth sides and bottom. The anemone is able to contract considerably into the cleft if threatened. They should not be in the direct flow from any powerhead or the like, the seawater flow is preferred to be gentle. In a reef system positioning would need some thought because of the high seawater flow, and at the same time remembering the anemone’s light requirements.

Having mentioned the anemone’s preferences, it would seem that this particular one is fussy. However, it is reported to be one of the easiest, or perhaps the easiest anemone to keep among the symbiotic types (symbiotic = anemone/clownfish).

There is one potential habit with this anemone that some aquarists face and others not – it can without apparent reason go wandering. Even though the anemone has been provided with all necessary requirements to settle, it could go for a walk which is not going to necessarily please the aquarist. It could end up a very short distance away from where it was placed, or it could end up down the back of rocks hardly on view and the like. Or it could stay exactly where put!

If the anemone does move to a position unacceptable to the aquarist it could be transferred to a new area which again is designed to meet all its needs. Care has to be taken, as the anemone could well be well fastened to a rock and clumsy attempts to release it could cause damage and affect its health. If at all possible, if the anemone is fastened to a rock, the rock should be moved to a new area with the anemone and be used in the construction of the new cleft. With a prayer for good luck maybe the anemone will stay put.

Feeding the anemone is easy, all that is required is a smallish piece of mussel, lancefish or the like. Once or twice a week the food is placed on the tentacles, and the anemone will transport it to the mouth. If a clownfish is present it is possible that the food will become of immediate interest and it may not reach the mouth, so this needs to be watched for.

The anemone could reach a diameter of 20 inches (circa 50.75 cm) though this is unlikely in an aquarium. Having said that, I once kept a symbiotic anemone of a different type that grew so large it had to go back to the local fish shop. Sadly, the clownfish also went with it.

As said, symbiotic anemones are not for the inexperienced. If including one in the display is being considered, then this one is reported to be a little ‘easier’. Watch out for walkabouts though!

The link provides some pictures.

http://www.poppe-images.com/images/search_results.php?keyword_mh=Entacmaea+quadricolor&x=54&y=12

The word invertebrate covers all those organisms that have neither an internal skeleton nor a backbone. They live on land and in the seas.

There are around 2,000,000 different species on the planet and in the region of 97% of these are invertebrates*. Invertebrates that live on dry land include those that are well known to us such as worms that are often dug up by the gardener and spiders who weave there webs in many places.

Common examples of marine invertebrates include well known life forms often kept in aquariums such as shrimps, crabs, anemones, worms and sponges. In the seas and oceans the invertebrate is everywhere, not only on the wild reefs in warm areas but in cold and very cold areas as well. These invertebrates can be minute to very large.

Invertebrates that have a hard exterior shell, such as the very popular shrimps, have a ready made defence somewhat like a knight of old. It gives a level of protection against predators. The battle between predator and prey is ongoing, and defences need to be updated (over very long periods) as the predators adapt to overcome the defence strategy.

It would seem that hard-shelled invertebrates have developed an excellent defensive system without many drawbacks. The defence is not totally adequate because of the constant danger from predators as mentioned, and there is another major disadvantage. Living things need to grow, and the hard skeleton of, for example, a shrimp is fixed in size. So there is only one way that the shrimp can obtain the room to grow, and that is to get rid of the current shell. This is done fairly regularly and once the old shell has been abandoned there is a new one of larger size beneath. Unfortunately the new exoskeleton is soft and time is required for it to harden. During the hardening period the shrimp is extra vulnerable and needs to hide away in a secure spot until hardening is complete.

In order to produce a good exoskeleton the shrimp (just to use the example above) needs to draw on the seawater for some materials. Fortunately, they should be available in reef aquariums where the aquarist is already maintaining adequate calcium and other levels, and a problem shouldn’t arise.

Finding the abandoned skeleton of a shrimp shows how remarkable the process of creating a new exoskeleton is, for the abandoned one has all the details of a living shrimp. This includes the long thin antennae and legs. The abandoned exoskeleton can appear a bit ‘floppy’ though which gives the game away.

I remember keeping an aquarium years ago that among other things contained a large anemone and a clownfish. A cleaner shrimp was also resident. One morning I approached the aquarium and was horrified to see that the anemone had apparently got the shrimp. It was amongst the tentacles, perfect but lifeless. I was quite irritated even though I knew that the anemone had predatory abilities. I visually searched the aquarium and there wasn’t a sign of a shrimp, and was actually debating whether to obtain another. Later, as I came to the aquarium to supply food, there was the shrimp sitting on its normal rock. I did end up getting another so that the original had a ‘friend’, they are better off with more than one.

Just out of interest, science thought that sunlight is necessary to all life forms but has had to amend that view. As has been shown on television, very deep in the sea beyond light penetration there are a few small areas of mild volcanic activity. They produce ‘chimneys’ from where the volcanic output escapes, not lava but a stream of heat and minute debris that looks like smoke. Living near these ‘chimneys’ are crabs, filter feeding worms, shrimps and sponges. They have adapted to the alien world so far from the surface and have no requirement for sunlight. The sun’s energy is replaced by the emitted heat and chemicals.

If the aquarium is suitable (this really means a captive reef though a fish only system is suitable dependant on seawater quality, fish inmates and the aquascaping), invertebrates make excellent interesting inhabitants. Many such as cleaner shrimps are commonly available. They usually require very careful acclimatization to the home aquarium seawater and must not be exposed to air.

(*Reference: Marine Invertebrates. Martyn Haywood & Sue Wells)

The brittle star has a small central body which is circular or nearly so, and attached to this body are five long slender arms which are flexible. They can move if necessary at quite a speed.

They are simple to feed. Most of the time, particularly at night, they will crawl about looking for anything that is edible, and so can perform a useful function in the aquarium. Supplementary feeding is usually required if the aquarium is reasonably clean because of good husbandry. This is easily achieved by placing one or two small pieces of defrosted fish or shrimp nearby – they will be detected very quickly and consumed. I’ve seen brittle stars fed a larger piece of fish and they still consume it, their body extending quite grossly. This isn’t good practice though.

There exist some brittle stars that are predatory, taking snails, shrimps and even other brittle stars. As always, the aquarist needs to be sure that the type being purchased is not a danger to other livestock. Most on sale however are generally safe with larger cohabitants of the captive reef but care must always be taken if small fish and shrimps are present.

When brittle stars are introduced to the aquarium they must not be allowed to come into contact with the air. They should be acclimatized slowly in the same way as a shrimp, preferably using the drip method, and then released underwater.

Bristle stars are generally hardy and straightforward to keep. It could be that in the early days after introduction to the aquarium the brittle star only appears at night. This is likely to change as time passes, particularly when food is introduced.

Brittle stars come with all sorts of coloured patterns and sizes. They are a ‘different’ inhabitant of the aquarium providing interest and can be comical at times. They can also seem quite alien.

The pictures on the link transmit an idea of what these creatures are. Clicking on the pictures will enlarge them.

http://www.goldenstateimages.com/GSI_search.php?srch=starfish%20brittle%20star&op=ex

In addition to various types of fish, there are snails, crabs and shrimps. The aquarist has to be sure any of these additions are safe – ‘safe’ in this instance means they will not damage or eat other livestock, and in turn other livestock will not damage or eat them. For instance, some crabs are not welcome as they blunder about the aquarium and knock things over or even attack and damage corals, and similarly some shrimps are not welcome in an aquarium with starfish as they will attack and eat them. Likewise a shrimp placed in an aquarium with certain fish is in great danger of being consumed. However, many snails are of use in the control of algae and some hermit crabs can be of use as general housekeepers.

There is a shrimp that is very often the first ‘diversion’ from fish that a fairly new aquarist with a reef aquarium will be attracted to and this is the cleaner shrimp, properly named Lysmata amboinensis. Have a look at the shrimp via the link:

http://www.oceanlight.com/lightbox.php?sp=Lysmata_amboinensis

It is commonly called the cleaner shrimp because of its fish cleaning actions on the wild reef. The shrimp, with a number of its namesakes, set up a cleaning station on the reef which becomes well known to many fish of all sorts. The fish will even patiently wait their turn if the cleaners are busy. These fish come to the cleaning station so that the shrimps can remove parasites, growths, loose scales and other irritants from the fish’s surface. The little shrimps even go inside the gills and mouth of the fish with the fish ‘opening wide’ to permit this. It would be a quick snack for the fish but presumably they recognize the shrimp from its markings and movements and let it be. I read of an experiment on a wild reef where cleaner stations were removed from a specific quite large area and the incidence of problems such as fish disease increased. When the cleaner stations were re-introduced the problems diminished.

If the shrimps are to be introduced to the home aquarium it is important that they are acclimatized properly. This means that seawater in the transport container is reduced by half and seawater from the aquarium is dripped into the container using an air line and air line clamp. The drips should be a little short of a continuous stream and the container allowed to fill to its previous level. Some aquarists then repeat the process. The shrimp should not be exposed to the air. They settle in quickly. It goes without saying that the aquarist must be sure there is nothing already in the aquarium that could threaten the welfare of the shrimp. The shrimps can be kept as a group if required.

The shrimps soon become a favourite pet as they quickly respond to the presence of the aquarist – expecting food no doubt – and will climb on the aquarist’s hand if this is in the aquarium. They probably see the hand as a fish and proceed to move about on it looking for food. Feeding them is easy as they will accept directly offered small pieces of de-frozen food such as lance fish and mussel etc. They will even attempt to capture pieces of flake food and can learn to be quite successful.

In the aquarium they may attempt to clean fish as they would on the reef but this may be an irritant to the fish. In the aquarium the fish cannot move away from the ‘cleaning station’ but usually they move away far enough and trouble does not arise.

The shrimp is ‘reef safe’ and the reef system is the place for it to be housed. Being in a reef system also allows the shrimp to molt securely. Molting is when the shrimp casts off the old exoskeleton and hardens off a new one. This occurs as the exoskeleton does not grow so the shrimp from time to time needs a larger one. If a ‘dead’ shrimp appears it could well be the result of molting.

The cleaner shrimp described is not the only one as there is another that is very similar in appearance. This one is properly called Lysmata grabhami. It displays the same colour pattern except that the white marks on the ‘tail’ are missing – the white line that runs down the top and centre of the body extends to the end of the ‘tail’.

Once established in the aquarium, which does not normally present any problems, the little shrimps are super. Not only are they colourful and a contrast to fish, they are very likeable because of their amusing and friendly antics.

Another interesting crab is the porcelain. This term is often thought to refer to one crab but this is incorrect, they are multiple. Their size is not a problem as they achieve around ¾” to 1¼”. There’s another two good reasons besides their size which makes them particularly interesting to marine aquarists. First, they are very colourful. Second, they usually reside in the tentacles of an anemone, or more unlikely down underneath it. So they are similar in that respect to clownfish.

Porcelain crabs come under various common names depending on which one it is. To take one in particular the common name is ‘dotted anemone crab’, or sometimes the general ‘porcelain crab’. The proper name is a tongue twisting Neopetrolisthes ohshimai.

http://www.geodia.com/gallery2/main.php?g2_view=keyalbum.KeywordAlbum&g2_keyword=crab&g2_itemId=132

They are best kept in a reef system, obviously with an anemone. Anemones such as those inhabited by clownfish are appropriate. Though one or two of this type of crab are able to defend their home against clownfish, this one is likely to lose out and it is best if the aquarist makes the choice – clownfish or crab. They are both suitable for inclusion with an anemone. It is best that one crab is kept as two of the same sex will fight.* If it is known that two are a pair then fine.

In a high quality habitat they are hardy, but it would be best for the aquarist to gain experience and feel confident about aquarium general maintenance including seawater quality before proceeding. This is not so much for the sake of the crab – experience is required for the sake of the anemone as, at least in my opinion, though I note quite a few others of experience agree, an anemone is not the ideal starter for a beginner. If an anemone and crab are to be kept, it should be remembered that the anemone requires the proper lighting, though this is likely to be present in a coral reef aquarium.

Feeding the crab is not difficult. The crab is a filter feeder and to facilitate this method the crab is able to spread hair-like fan structures into the seawater. So to feed them the aquarist could target liquidized filter type foods over them. This needn’t worry aquarists however, as the crabs will also take small pieces of de-frosted food such as lance fish, shrimp etc. The crab will not require much food though feeding should be fairly regular, and any extra food the crab ignores will probably be caught by the anemone, which in turn requires feeding with the same kind of food in larger pieces but less often.

When considering livestock for an anemone, clownfish of various types are probably the choice of most aquarists. If a crab such as that described is chosen then the interest is just as high and the sight of the two life forms co-existing just as fascinating.

(*Ref: Marine Atlas. Helmut Debelius & Hans A Baensch)

There are some crabs however that often find favour with aquarists, and these are the hermits. They are quite comical as they wander about the aquarium, and at the same time are useful as scavengers. They can be colourful too, though this is usually the legs as this is the part that can be seen. The shell is not the crab’s own; it has been found empty or taken over from a snail for example. The crab keeps itself secure in its shell with a tenacious grip. If excessive force is used to remove the crab, then the grip will not be broken, but the crab’s body will break apart. The grip is so strong because remaining in the shell means survival, outside of it means death as the crab is highly vulnerable. The crab holds itself inside the shell with its rear pair of legs which slant forward to increase strength, and in addition the abdomen is shaped to fit the shell reasonably.

This is one danger from the hermit crabs, their need for a shell. I once had a large snail and a hermit crab in the same 4ft aquarium and for a while all went well. However, the hermit began following the snail about, trying to get at its flesh and generally upset it. Eventually it damaged the snail which died. The hermit crab was next seen in the snail’s shell. Though I couldn’t be sure, I wondered if I was at fault, perhaps the hermit had grown and needed a larger home. I would suggest that a small selection of suitable shells is left in the aquarium, so that hermit crabs can change home if they have a need.

There are several suitable hermit crabs for the aquarium, and provided there are no dangers present (such as for example puffer fish) a fish only system could be used, though there needs to be rocky structures present. The best habitat however is a reef system, where the crab can find security and its ‘cleaning’ activities are perhaps the most useful.

The hermit crab being focused on here is commonly called the white spot hermit crab, or the scarlet hermit crab, or the knobby hermit crab. There may be more common names demonstrating that for identification purposes the proper name is the best. In this case the proper name is Dardanus megistos.

http://decapoda.free.fr/illustration.php?n=5&sp=225

It is necessary with this crab for the reef to be securely built, though this generally applies to all hermits, particularly the larger ones. They are not particularly naturally destructive, but just clumsy. They could grow to around 4″ (circa 10cm) including and dependant on the shell they inhabit. Only one should really be kept or it is likely fights will occur. It is also necessary to exclude shrimps in general as the crab could eat them. The hermit crab should be seen during the ‘lights-on’ period but is also active at night. They are hardy in a good habitat.

Feeding is simple as the hermit crab appears forever hungry, constantly looking for food. They will take de-frozen lance fish, mussel flesh, crab meat, and almost anything else that is edible. Hence they are fairly good at cleaning up.

This particular hermit crab is not suitable for a small aquarium; one of around 4ft (circa 122cm) should be fine. Though the crab population should be restricted to one, an aquarium of this size affords space for other inhabitants to spread interest.

This is one species of hermit crab which is interesting and colourful. However, if the aquarist wishes to keep more than one, or keep one in a smaller aquarium, there are types that could be available. For example, there is the red reef hermit crab, proper name Paguristes cadenati. This could grow to around 1½” (circa 4cm). A trip to the local fish shop (LFS) is likely to turn up hermit crabs that are suitable for the aquarist’s particular system.

With proper attention to the habitat and some to other livestock, the hermit crabs are as said useful, interesting, amusing and hardy. Additionally they pose no problems with feeding. All they require is a new home occasionally.

Before starting, a picture is needed:

http://fr.reeflex.net/tiere/1019_Rhynchocinetes_uritai.htm

This shrimp comes under a few common names which could lead to confusion: dancing shrimp, rosy dancing shrimp, camel back shrimp and common dancing shrimp being some of them. The proper name is Rhynchocinetes uritai.

They’re lovely to look at and one of the common names – ‘camel back shrimp’ – refers to the clear hump on the back. Another common name – ‘dancing shrimp’ – refers to the jerky way in which they move.

The shrimp is social and can be kept in a group. They do not usually have any trouble with other commonly kept shrimp except perhaps the boxing shrimps, Stenopus sp. Obviously the number kept depends on the size of the aquarium – two could be kept in a relatively small system.

The best habitat for the shrimp is a reef aquarium as this affords all the crevices and caves that are needed. There shouldn’t be any other livestock that could threaten the shrimp of course. Keeping the shrimp in a reef aquarium does have a potential drawback though, and that is the shrimp could ‘have a go’ at soft corals, including colonial anemones. Then again, many aquarists do not have this problem. Hard coral types are usually left alone.

There is another possible advantage to having these shrimps. Please note the word ‘possible’. This concerns that unloved nuisance of many aquarists aiptasia. These anemones are often introduced on the rock of a new coral, or with live rock. After a time during which the anemones spread, an ongoing battle usually takes place between the aquarist and the anemones. This battle usually ends with the aquarist being in control generally but having to periodically re-attack. An uneasy truce could describe it. There have been anecdotal reports on the internet that these shrimps attack aiptasia, mainly young ones. It has also been reported just as often (to my knowledge) that the shrimp ignore the anemones! I haven’t seen any reports following controlled experiments. Perhaps they will, perhaps they won’t.

Generally the shrimps are more timid than other commonly kept types and avoid the bright light of a reef system, initially anyway. They should settle down and be seen more often, though they usually retain their preference for dimmer light. It is more unlikely that they will rise to take food so the aquarist may have to target feed the shrimp. This is not difficult, not least because they will take the usual fare such as de-frozen lance fish, mussel etc. They may well chase brine and mysis shrimp that have been released as food.

As with other shrimps they will shed their exoskeleton from time to time. This is to permit growth. A new exoskeleton will harden over a fairly short period and the old one looks like a shrimp albeit a dead one.

All shrimps need careful acclimatization to the new home aquarium and it is reported that this one is perhaps more sensitive. Therefore transfer to the new seawater should be completed with care. Empty out half of the seawater in the transport container. Then, using an air tube and air tube clamp, drip aquarium seawater into the container until it reaches the previous level. The drip rate is a little short of a slow continuous trickle. It is probably worthwhile carrying out this procedure twice. When the shrimp is introduced to the aquarium it must not be exposed to air. It is also worthwhile switching off the main lights for a day – this period will not harm any corals.

The dancing shrimp in the proper habitat is a delight. They will probably not be seen as often as other types. For those aquarists who battle the troublesome aiptasia wouldn’t it be great if all the anemones disappeared. No guarantee though.