Dear Jason,

There are international laws preventing the trade in some endangered species such as elephant ivory and turtle shells but such examples are very rare. Individual countries have laws banning the collection of particular species but they are often complicated and difficult to enforce.

I am afraid nudibranchs have become a 'by catch' in the aquarium trade which are mainly concerned with tropical fish and what they curiously call 'live rock'. Any aquarium shop that says nudibranchs are easy to keep in aquaria and are herbivorous is at worst lying and at best doesn't know what they are talking about. See my earlier comments on keeping slugs in captivity.

In particular, species of Phyllidia are likely to fight back and cause great problems if put into aquaria [see my comments in message #23360]

Best wishes,
Bill Rudman

Dear Jupiter,

This is a type of slug which I definitely wouldn't advise for an aquarium. In fact there is a message on the Forum from some years ago which is probably the same species as yours [#9376]. In that message I say:

"In my opinion this is a definite no-no in any aquaria. I can't tell from the photo just which species it is, perhaps Phyllidiella pustulosa, but it is a member of the Phyllidiidae. Species of this family exude a milky white secretion which is highly toxic, and recently collected - that is healthy - specimens can kill everything in an aquarium just from their secretions dissolving in the water. [see earlier message]. They are also sponge feeders. The good news is that your animal is probably starving and so is probably unable to produce the toxic secretions. Be that as it may, I think it is highly irresponsible of aquarium shops (aka LFS) to sell potentially toxic animals to unsuspecting customers."

I am afraid there is not a lot more to say. Apart from potentially poisoning other animals in your aquarium, it is a very specialised sponge-feeder, feeding on only a few species of sponge. We know very little about the biology of these slugs so I cant tell you which sponges they eat, and even if I could, it would be most unlikely that you could buy any from a pet shop.

Sorry for bad news,
Bill Rudman

Dear Mattias,

There is one record on the Forum of this species feeding on a sponge, probably Petrosaspongia [message #12039] and I suspect it feeds on a similar or the same sponge seen in messages #12040, #11903, but sponges are very difficult to keep alive in aquaria and almost impossible to transplant from the wild into aquaria under the best circumstances. Certainly the chances of one being kept alive from Bali to Uppsala are extremely slight. Of course the chances of some fish collector in Bali getting the right sponge is also very slight as well. And then even if you had the sponge alive in your aquarium you would then be going to put it under the stress of being eaten alive. The picture I am trying to paint is one of impossibility.

If someone could invent an artificial food for sponge feeders I am sure they would make a fortune, but it seems that sponge feeders have evolved to feed on particular species of sponges - not just because they like certain tastes, but because different sponges contain different metabolites the nudibranchs require, and others  contain symbiotic organsims which also seem essential for some sponge feeders. Although farmers can feed quite a few vegetarian farm animals on hay, it seems sponge feeders have more complicated requirements. I am afraid your nudibranchs have been condemned to a slow starvation.

Sorry,
Bill Rudman

Dear Joshua,
Your animal is, or rather, was, Hypselodoris bullocki, or at least something closely related. As you'll see from the correspondence on that page, and this page. these animals are sponge feeders, and most species feed only on one or a very few sponges particular to them. I can't say if the aquarium shops are deliberately misleading you, I suspect they just don't know. Either way it is inexcusable. People selling live animals have a responsibility to know how to care for them, and to pass correct information on to customers. Imagine the outcry if they told buyers of kittens and puppies that all you need to feed them is a handful of grass each day!

Best wishes
Bill Rudman

Dear Alan,
Thanks for thinking of us. I checked it out and it seems to be a frozen food which I guess is ok for biting animals when it thaws, but the 'teeth' of slugs are not on jaws but on a tongue-like ribbon, so to feed they would need a solid block to scrape on. However I guess anything's worth a try
Best wishes
Bill Rudman

Dear Steve,
These animals eat sponges, but the critical thing is that they will only eat one or two particular species of sponges. Unless you know what that particular sponge is and have access to living supplies of it, the nudibranch will starve. Species of Hypselodoris don't eat plankton. Concerning their toxicity - they have mantle glands which contain noxious molecules, but they are usually only released when thea animal is physically damaged. As fish don't like the taste of the chemicals they are unlikely to eat enough of them to be poisoned. The aim of the glands is to prevent the slug being eaten. It's not much value to the slug to kill the fish after it has been eaten. On the other hand phyllidiids certainly have much more noxious molecules in their glands. Again they are protective, but they are often exuded from the slug's skin when it is stressed, often on occasions when they are not being attacked by a predator. These chemicals can definitely can kill fish in the surrounding water.

As I said recently to someone else, now that you have the slug you might as well keep it until it dies. It will cause no more damage to the water quality when it dies than any other organism in your tank - but let the store guy know that stocking live nudibranchs for sale is not very responsible
Best wishes
Bill Rudman

Dear Susanne,
I am sorry to be the bearer of bad news, but nothing has changed, they require specific sponges which are just not available to the aquarium trade and even if they were, the logistics of keeping colonies alive in home aquaria would not be feasible.

Concerning their toxicity. They do have defensive mantle glands with distasteful chemicals but I can't imagine they would be a problem, in your aquarium. I guess you may as well keep them in your aquarium until they die. Albert Jenner's 'porcelain chair' alternative [message #12443] - which I assume is his delicate way of saying 'flushing them down the toilet' - seems rather a waste.
Best wishes
Bill Rudman

Dear Shoei,
On the whole, sea slugs are not good pet material for the uninitiated. Most have very special needs and are very particular in the food they eat. Most you see in aquariuum shops are quietly and slowly starving to death
Best wishes
Bill Rudman

Dear David,
The story with C. joshi is probably worse than with H. bullocki. We have photos of the sponge H. bullocki feeds on, but C. joshi has been seldom seen and we know nothing of its food, which is almost certainly a sponge.

And finally your black and green slug. In my opinion this is a definite no-no in any aquaria. I can't tell from the photo just which species it is, perhaps Phyllidiella pustulosa, but it is a member of the Phyllidiidae. Species of this family exude a milky white secretion which is highly toxic, and recently collected - that is healthy - specimens can kill everything in an aquarium just from their secretions dissolving in the water. [see earlier message]. They are also sponge feeders. The good news is that your animal is probably starving and so is probably unable to produce the toxic secretions. Be that as it may, I think it is highly irresponsible of aquarium shops (aka LFS) to sell potentially toxic animals to unsuspecting customers.
Sorry I can't be more positive,
Cheers,
Bill Rudman

Dear Jenifer,
I would need a photo of the slugs and the eggs - or a reasonable drawing - before could say anything sensible about your animals. Your mention of 'spikes' on the back sound more like a species of Elysia or Placida rather than an Elysia. Whatever you have the eggs are only likelt to cause a population explosion if the larvae hatch, and if they do hatch, they need to survive and develop into slugs. Most sea slugs have larvae that spend some time swimming in the sea feeding on microscopic plants. These larvae are very difficult to keep alive in aquaria. However there are a few species, such as Elysia crispata, whose larvae do survive in aquaria, much to the delight of their owners [see Joe's recent message].

I am afraid without further clues, I can't give you much advice. Perhaps a photo, or some idea where in the world the Caulerpa came from would be a help. My advice would be to wait and see what happens. It could be interesting. I don't know of anyone whose tank has been over run by a sacoglossan sea slug so you are unlikely to end up with a major problem.
Best wishes,
Bill Rudman

Dear Jim,
I don't usually post advertisments for the aquarium trade but your message gives me a chance to reply to the misinformation which the trade is spreading either through ignorance or design. To say as you do that red algae is a "great feed for many marine slugs" is incredibly misleading. As far as I know ONLY Sea Hares, such as Aplysia, will eat it. Other herbivorous sea slugs, such as the sacoglossans, each have very specialised diets, and as far as I know none feed on Gracilaria. Most people who want to keep sea slugs in aquaria, want to keep the bright colourful nudibranchs, and ALL of those are CARNIVORES, quite unable to and quite unwilling to eat Gracillaria or any sea weed, no matter how juicily prepared.

Please stop perpetuating this myth that nudibranchs are easy to keep in home aquaria, because they feed on sea weed. It is untrue and is encouraging a trade which can only help destroy tropical environments and starve many nudibranchs.
Best wishes,
Bill Rudman

Dear Andy,
I'm afraid large anemones are always a bit of a problem. I doubt if slugs will actually crawl into them but sometimes slugs do strange things like drift in the water then drop ... , or lower themselves by mucous thread straight on to an anemone. I remember once losing a new species to a large anemone - which regurgitated it a few days later so at least I was able to look at its radular teeth.

Can't really give any advice. Large anemones are good if you want to keep their commensal fish and shrimps happy - but they are a bit of a trap for other life.
Best wishes,
Bill Rudman

Dear Raymond,
I suspect your animals are a nudibranch of the family Phyllidiidae. Have a look at the page on Phyllidia varicosa. If I am right the slime they exuded from the upper surface when you first got them would have been a white stringy sort of substance. If so, you were lucky they exuded this before they had much contact with your aquarium because the chemicals they exude can be quite toxic to aquarium fish and when freshly caught if the aquarium they are in is left in a closed room there air can become so acrid that your eyes can start streaming and stinging.

Phyllidiids like all nudibranchs are carnivores, in the case of phyllidiids, each species feeds on specific sponges. The chances of matching your slug with its correct food sponge are slight to non-existent. I suppose you should confirm that your slugs are phyllidiids before I suggest what you should say to the person who sold you these as algal eaters. One final check would be to check on the underside of the body to see if it has gills in the gap between the foot and the mantle. [If you look at the page on Torsion and gills there is a photo on the bottom left of Phyllidia ocellata showing typical Phyllidia gills].
Best wishes,
Bill Rudman

Dear Sarah,
You may have gathered from various comments I have made on the Forum that I am not in favour of people keeping sea slugs in aquaria. I am not in favour of people thinking they can get instant gratification by going to their local shop and buying a beautiful animal which will live without food forever.

I am fully in favour of people like you who have ready access to the sea and wish to learn more about these animals by bringing one or two home. You can learn a lot about their biology - sometimes new information - by carefully observing them and learning to care for them. With ready access to the sea it is much easier to test possible food organisms and replace the food if or when it dies.

To answer your questions:
• Dolabrifera:
From Brad's message Dolabrifera seem to live quite happily in aquaria. I am not sure what algae it feeds on naturally but I am sure it will eat the bacterial and algal film that grow over surfaces in aquaria. Certainly some natural rock surfaces would be more comfortable for it than a shiny glass surface. I am not sure what your 'ear seaweed' is but if its name is based on its shape it sounds like the brown algae Padina. I'm pretty sure Stylocheilus doesn't eat this, and more importantly browns are a bit of a problem in aquaria as they exude many nasty chemicals. It could be why your Dolabrifera doesn't seem too happy.
• Hexabranchus:
As long as your Hexabranchus is not too large it should be ok if you can find a sponge it will eat. If you go to the Hexabranchus page you will see a link to a page of references on its biology. [There is at least one reference to The Veliger which should be available in your museum or local university library]. It apparently feeds on a variety of sponges - so again the problem is finding one it will eat and which is common to replace regularly in your aquarium, or hardy enough to survive in your aquarium even when under attack by the Hexabranchus. Its certainly worth a go, but you will need to approach it slowly and systematically. Finding what things eat and how to keep them alive in an aquarium can be a rewarding experience.
Good Luck,
Bill Rudman

Dear Jennifer,
Most messages on the Forum apply to a single species, so it's fairly clear from the context whether we know what a particular species feeds on or not. The big problem, even when we know what a species eats, is how to get a continuing supply of its food so that it stays alive and healthy long-term. Many nudibranchs feed on sponges, bryozoans, hydroids and other colonial animals, which are particularly difficult to keep alive in artificial conditions, especially when we want them to be attacked and gradually eaten alive by our favourite nudibranch. A second problem is that even if we know the food of our favourite nudibranch by name, it is often not easy to identify it or to obtain it from commercial sources.

Most nudibranchs available in aquarium shops have been collected by chance by some poor islander in the tropics who is happy to make a few cents by on-selling their colourful find to the first middle-man in a chain of people which stretches halfway around the world. The last person in the chain is your helpful aquarium shop owner. These animals are not collected in an organised way and there is no system of collecting their specific food organisms, so the possibility of your aquarium shop owner, however reputable, being able to provide you with the correct food item on a continuing basis is nil.

Your mention of a message mentioning the Breadcrumb sponge as an alternative food source for Hypselodoris bullocki illustrates the potential for misinformation to circulate. Common names are impossible to use as they mean different species to different people. If, as suggested, the name 'Breadcrumb sponge' was referring to a species of Haliclona, then it is most unlikely that it would be a suitable food for a chromodorid such as H. bullocki, because chromodorids have never been found feeding on Haliclona or related spiculate sponges.

If your heart is set on a nudibranch, and the only way you can get one is to buy one, then all I can suggest is that you ask your local supplier to sell you the one he has in his home tank and to sell you the food he has been using to keep it alive and healthy.

As far as I know there are no artificial foods available
Best wishes,
Bill Rudman

Thanks Dave,
Sounds like a good resource for aquarium keepers - let's hope it relieves the pressure a bit!
Bill Rudman

Dear Alisa,
I'm afraid I can't recommend keeping nudibranch in aquaria because of the difficulty in feeding them. Have a look at the other messages below yours on this page where I discuss very aspects of the problem. A alternative to a nudibranch would be a Sea Hare. Being herbivorous, they would probably help with keeping weed growth down in the aquarium.

Another indicator that a sea slug would not be a good idea is your mention of a clown fish and a banded coral shrimp. Do you have an anemone for them? If so slugs often fall into large anemones - they crawl up the sides, start crawling upside down on the water surface and drop off. Commensal shrimps can also be very aggressive and will quickly 'pick' a nudibranch to death.

So I guess my advice is to perhaps avoid sea slug in your aquarium.
Best wishes,
Bill Rudman

Dear Mike,
I am glad the word is spreading. Good Luck with your efforts.
Bill Rudman

Dear Melinda,
The short answer is don't. Unless you can find a species which you can feed regularly there is no point in trying. If you are working from bought specimens I don't encourage it because the shopkeepers don't know what they are doing. The only people who successfully keep nudibranchs alive are those who are close to the sea, can collect them themselves, can find out themselves what they eat and regularly provide fresh food. I am sorry to be negative about this, but it is only a few years ago that most tropical marine fish could not be kept alive by amateurs. Only after much trial and error and research were appropriate supplementary foods developed which could make up for the loss of their real diets. At present we don't even know the 'real' diets of most nudibranchs so finding substitute foods has still a long way to go.
Best wishes,
Bill Rudman

Dear Lorena,
I am not sure if your interest is for research or for keeping nudibranchs in a home aquarium. Have a look at the messages on the Keeping in captivity page and also look at the pages on Berghia verrucicornis and Hypselodoris bullocki which are two species which have generated a lot of discussion among aquarium keepers
Best wishes,
Bill Rudman

Dear Tina,
Have a look at two general pages on the Forum which will give you a lead in to other information on the site. Try the Defensive Glands Page and the Opisthobranch Defence Mechanisms pages. Sacoglossans, like many sea slugs have two main means of defence, one is to hide and the other is to taste very nasty. Most hide, or become nearly invisible by being coloured almost identically to the green algae on which they feed. To taste inedible, many species either produce chemicals which they store in glands or sacs in their skin, or they reuse molecules they have removed from the plants on which they feed. Have a look at my message on Elysiella pusilla for an example of chemical defence. Cynthia Trowbridge also lets us know about some more examples in another message worth looking at.

Concerning the safety of Elysia crispata or other similar slug in an aquarium. It is definitely not a natural environment and animals can 'misbehave'. Although I haven't kept an aquarium with fish for many years, I wouldn't trust a wrasse or a trigger fish even if I was sitting there watching them. The problem with chemical defences is that they only work if the predator knows the potential prey tastes bad. And the usual way for it to learn is to bite or 'mouth' the hapless prey. Even if the predator finds the prey too distasteful to eat and spits it out, it is often badly damaged. In nature we assume the benefit is not for the individual who gets 'tasted' but to the remaining population of the prey animal which hopefully won't now be tasted. In an aquarium, where you may only have one or two of the prey animals, the whole system of defence, which relies on a few prey animals being sacrificed to train the predators to leave the rest alone breaks down.

I'm afraid my advice would be to keep sea slugs and carnivorous or aggressive fish in separate tanks.
Best wishes,
Bill Rudman

Dear Kyle,
The scientific name of the Spanish Dancer is Hexabranchus sanguineus. Have a look at the messages on the Hexabranchus sanguineus page. You will find information there on its biology. You will find that it eats a variety of tropical sponges, none of which will be available for sale. Have a look at the Hypselodoris bullocki pages and the general page for further discussions on keeping nudibranchs in captivity and complaints from people who have bought nudibranchs from tropical fish stores.

You will see from my comments on those pages that I don't think it is a very good idea buying and selling nudibranchs, because 99% of them will die because neither the traders nor the aquariists have any knowledge on keeping them in captivity. All nudibranchs are carnivorous and every species has a very special diet. Even if we did know what each species ate, in most cases it would be a sponge, soft coral, bryozoan or some other delicate colonial animal which you couldn't buy, and even if you could, you couldn't easily keep alive in an aquarium.

If there is a aquarium fish traders association in the USA I think you should protest to them about this trade. You are being tricked by collectors and traders in Indonesia and other places in the tropics into buying and stocking animals that you can't keep alive. As your customers begin to learn that they can't keep these animals alive, they are going to get depressed and blame sellers like you, which won't be good for your reputation. My advice would be to stop stocking nudibranchs, tell your customers why, and alert other shop keepers like you to the problem.
Best wishes,
Bill Rudman

Dear Robin,
A question. What does LFS stand for? Is it aquarium trade jargon for 'live fish supplier' or something like that?

Now to identify your animal. I really need a few more clues. Does it look like Phyllidia madangensis? If so have a look at the other species in the Species List which are in the Family Phyllidiidae until you find a match or else take a photo and send it to me.

If it is a Phyllidia then I am afraid it is not an algae eater but a specialised sponge feeder. If could also cause problems in your tank by secreting nasty poisons into the water. But I can't really advise you until I see a drawing or a photo.

I am afraid aquarium fish sellers apparently are saying that nudibranchs are algal feeders so that you will buy them. All nudibranchs are carnivores, that is they eat animals, each species feeding on a very specialised diet which your aquarium shop will not have in stock. Have a look at the conversation I am having with Cody Mott at the moment on this very topic.
Best wishes,
Bill Rudman

Dear John,
Thanks for your detailed observations on your Hypselodoris bullocki. I guess the first thing to say is that it is a sponge feeder, and all its relatives are sponge feeders.So how can we interpret your observations? One possibility is that the 'hairs' of the filimentous green algae are acting as filters and becoming coated with a layer of organic matter which attracts the nudibranch. A more likely explanation, I'm afraid, is that you animal is starving. To get to your fish shop in the eastern USA it would have been collected somewhere in the Pacific and then shipped to the USA. At a minimum I would suspect it has been without real food for 2-3 weeks. Hypselodoris feeds by rocking its rasping tongue-like radula out of its mouth where it scrapes off a layer of food sponge. This is a fairly rhythmic activity which you can often see these animals doing as they crawl along the side of an aquarium.

I wish I could say that it looks like they do eat filamentous algae for food, but I suspect that your animal is operating on 'automatic' whether what it is eating is suitable food or not. In spite of my views, please keep us informed of your animal's progress. There is always the possibility you have made a great discovery.

Best wishes,
Bill Rudman.

Dear Darla,
Glad to be of help.
Bill Rudman.

Thanks Darla,
I suspect the sponge food is food for sponges, rather than food made from sponges.

Concerning the normal life span of these animals. Have a look at the page on lifespans. There is not a lot there yet, but you will get a general idea. Most nudibranchs probably live just a bit less than a year but rhere are some known exceptions which I mention in messages on that page.

Any information anyone has that could be added to that page would be very welcome.

Best wishes,
Bill Rudman.

Dear Darla,
Shops shouldn't be allowed to sell things they know nothing about. If these animals you have bought are chromodorid nudibranchs then they are not vegetarian but specialised feeders on sponges. Have a look at the page on Hypselodoris bullocki and see if one of the photos matches your animal. If it is you will find messages and discussions on that page about keeping them in captivity. Also have a look at the messages below yours on this page which is a general place for messages concerned with keeping sea slugs in captivity.

I'm sorry you had problems sending a photo of the other animal. Send it to me attached to an email and I will have a look at it.
best wishes,
Bill Rudman.

Dear Darla,
You were lucky to get an instant response, sometimes it takes a week or longer. Your second animal is Chromodoris magnifica. Like Hypselodoris bullocki it is in the Family Chromodorididae, but as far as I know, nothing is known of the actual sponge it feeds on.

Although in nature these nudibranchs are very choosy about which sponge they feed on, it is possible that there is a species of sponge in your area that these two animals will feed on. It is unlikely that the sponge fishes commercially will be suitable, and even more unlikely that the psonge fisherman will know much about non commercial species of sponge. The other problem is that even if you find a suitable species of sponge you will need to be able to transplant it into your aquarium and keep it alive, which would be a difficult task, even if it wasn't being eaten by a nudibranch at the same time.

No I never heard from Laura Romin. It is unlikely that your animals would survive if you released them into the wild. The chances of them finding a suitable sponge would be very slight. More importantly I would not advise the release of any non-native plant or animal into the sea. Although in this case they are unlikely to survive, it is possible they mated before they were so rudely removed from the western Pacific and so could lay eggs and release larvae which would have a better chance of finding an alternative food source. A more likely problem could be the chance they carry some pathogen, virus etc, which while not lethal to them could affect local species.

As I said to someone else recently, you may as well keep them. They could live without feeding for some weeks, and you could use them as a talking point with visitors to warn against buying unknown animals from unscrupulous pet shops.

Best wishes,
Bill Rudman.

Dear Cherish,
I'm afraid you will have to ask your teacher what they mean by a "purple sea slug". Common names don't mean much unless they are in 'common' use, and I have never heard of a "purple sea slug".

If you have a photo or a scientific name then perhaps I could help.
Best wishes,
Bill Rudman.

Dear Steven,
As you'll see from other messages below yours on this page keeping nudibranchs in aquaria is not very easy.

Concerning breeding. They are hermaphrodites, which means they have a fully functioning set of male and female organs but they are not self-fertilising. In many species the male organs are functional much earlier than the female parts and it seems that sperm is exchanged and stored for some time before eggs are ready to be fertilised. If your animal has laid eggs they were probably fertilised before the animal was rudely removed from its natural environment.

Another feature of Sea Slugs is that they often lay eggs as a reponse to a shock or trauma. I often find that within a few hours of collection, specimens will lay and egg ribbon. However don't get your hopes up about breeding a herd of babies. Sometimes eggs laid like this are infertile, and even if they are fertile the chances are that the embryos will hatch out as free-swimming veliger larvae which you will be unable to keep alive.

To see some pictures of different sorts of Sea Slug egg masses go to the SEARCH button at the top of the page and type in egg or eggs. You will get a long list of egg photos in the Forum. Use the SEARCH button to look for information on larva, and also go to the General Topics Index.

Best wishes,
Bill Rudman.

Dear Mike,
If the slugs are like the one in the banner they are Chromodoris elisabethina which feed on particular species of sponges. Nudibranchs aren't very good animals for aquaria because most have very specialised food requirements. There are some that feed on hard corals, others that feed on soft corals, some that feed on anemones etc etc. Most of their various foods are colonial animals and themselves difficult to keep in aquaria.

Usually, the only people who can easily keep nudibranchs alive in aquaria are scuba divers or regular visitors to the shore who can colect their own nudibranchs and replace their food on a regular basis. One alternative to nudibranchs are Sea Hares which are herbivorous sea slugs and so can be fed more easily. Some pages worth looking at are:
•Keeping in captivity
•Hypselodoris bullocki
•Chelidonura varians
•Berghi verrucicornis

All of these pages have messages and discussions on keeping sea slugs in aquaria.

Hope they are of some use,
Best wishes,
Bill Rudman.

Dear Phanor,
Colombia, with coasts on both sides of the Panama Isthmus must be a very interesting place to study marine biology. I don't know of any books specifically on that fauna but I suspect you should have a look at the books on the nudibranch fauna of North America, such as Dave Behrens' Pacific Coast Nudibranchs (2nd Edition, 1991) which covers the fauna from Alaska to Baja California.

Also have a look at the sections on Pan American Nudibranchs & Pacific Coast Nudibranchs in Mike Miller's Slug Site at http://slugsite.tierranet.com/

My advice though, is not to choose the nudibranch you would like to put in your tank, before you actually see what nudibranchs you can easily find. Unfortunately even the 'most common' nudibranchs can be impossible to find when you actually want one. I would think that part of your project is to do some research on the natural history of the animals you are keeping in your aquarium, and finding out how to keep them alive would be good start.

What I would suggest is you go and look for some common nudibranchs, either intertidally or subtidally, remembering that you may need to replace your animals if they die. You are almost certainly going to have to replace their food many times, if you are going to keep them alive.

You will see from the Sea Slug Forum, and other sources, that nudibranchs all have very specific diets and most feed on other animals that are difficult to keep alive in aquaria. If the animal you choose feeds on a sponge, try and find small colonies of the sponge on removable rocks which can be placed in the aquarium without damage to the colony. You will need to check the colony regularly and remove it if it looks unhealthy so it doesn't contaminate the water. Alternatively you are going to have to find a nudibranch which feeds on a sponge species that you can easily collect every day, or so, to replace the one in the aquarium. I had a student working on a chromdorid nudibranch with direct developing juveniles, and he had to collect a sponge colony daily and break it into pieces to feed his juveniles. It is possible, but time consuming.

The same applies to nudibranchs feeding on hydroids, sea anemones, soft corals etc. Some anemone-feeding nudibranchs are quite good in aquaria because they feed on a variety of anemones, and anemones are relatively easy to keep in aquaria. You may also be lucky and find an aeolid like Hermissenda crassicornis which is a more generalist feeder and can be fed artificially in aquaria.

I would think the first thing you should do then, is find somewhere you can get to easily, as you may have to return many times, and then choose some nudibranchs that are relatively easy to find there. Hopefully they will be on or near some possible food so you can make an informed guess at what they eat.

If you find some nudibranchs you think could be easy to keep alive, you could then send some photos to the Forum and we could see if anyone can help you with information on their identity and natural history. We probably won't know anything about the natural history of the animals you find, but we can probably give you some clues on what they are likely to do or feed on. In that way you will be able to do some original research which will of interest to us all.

Best wishes, and good luck,
Bill Rudman.

Dear Adam,
I'm afraid you are not giving me many clues. The fanlike tail could be the gills of a dorid nudibranch, but have a look at the photo of Ceratosoma amoena to see where dorid nudibranch gills are situated, and what they look like. Failing that, the tail could be the feeding tentacles of a Sea Cucumber or even a fan worm. Sometimes fanworms can leave their tubes .... but that would be fairly risky business if you have fish in your tank. If it is an inch long you should be able to see if it has head tentacles or rhinophores which would pretty much confirm it is a dorid nudibranch. Another thing to look for is whether it has a foot. Sea cucumbers are essentially cylindrical and move by small tubular 'feet' much like a starfish.

If it is a dorid nudibranch it probably came with the rock as a recently settled larva on one of the sponge colonies which you say is now flourishing. Whatever it is, it is unlikely to cause harm, other than to eat a bit of one of the sponge colonies. Since 'live rock' is always a bit of a lottery I think you should give the beast a bit of a chance too. It has survived a fairly perilous few weeks being transported to your tank. Apart from natural curiosity in knowing what it will become, I think it deserves a second chance to prove itself.

Let us know if you succeed in confirming what it is. If a nudibranch, perhaps we can identify it for you. One possibility would be either Dendrodoris fumata or Dendrodoris nigra, both of which can be black.

Bill Rudman.

Dear Eirik,
The biggest problem, as you suggest, is that all nudibranchs are carnivores, and each has a very specialised diet. Most feed on colonial animals like sponges, ascidians, corals, hydroids etc and so even if you can identify the correct colonial prey and keep it alive in your aquarium, the nature of nudibranch feeding - gradually 'nibbling' at the colony - means that the colony becomes very stressed and so dies before it is completely eaten.

You have shown you can successfully keep green algae alive so sacoglossans would be a possibility. But again you would need to get some animals and then find the right food.

My feeling is perhaps you should think about keeping some Norwegian nudibranchs. There are some quite beautiful species. Perhaps you could contact Jussi Evertsen, who could give you some advice on finding them in Norway.

Jussi Evertsen
Trondhjem Biological Station
Department of Natural History
NTNU
7034 Trondheim
Norway
Email: jussie@stud.ntnu.no

Best wishes,
Bill Rudman.

Dear Theresa,
I'm afraid there is no simple answer to your question. Most nudibranchs have very specialised diets and most of their preferred foods are difficult to keep alive in aquaria. If you want more information on feeding go to the Search the Forum page and type in food or feeding and you will get a list of pages with relevant information.

On your specific question about eating your corals and soft-corals. I'm afraid there is no gentle way to be eaten. If a coral-eating nudibranch eats enough of a coral colony, the coral will die.

Best wishes,
bill Rudman.

Dear Rob,
Apart from the phyllidiids, which are a special case, the general problem with keeping nudibranchs in aquaria is the problem of feeding them. Sponges, hydroids, sea anemones, ascidians and bryozoans are all food of particular nudibranchs and all are difficult to keep alive in aquaria, especially if they are regularly being nibbled on!

I know dedicated aquarium keepers who keep chromodorids in aquaria, but that requires finding them alive on a particular sponge that can also be transplanted into the aquarium. It also requires you to regularly replace the sponge with another healthy sponge of the same species. [To distinguish what a chromodorid looks like, look at any of the species listed under Chromodorididae in the Species List]. Some aeolids are also amenable to aquarium life but again you need to identify their food. There is one species in New South Wales, Austraeolis cacaotica which seems to be a generalist feeder but most are very specific feeders.

Sorry I can't give you an instant recipe for success but if you are keen, think of it as a challenge. I'm happy to give some advice if you find something which seems to be working, but I would need a photograph.
Best wishes
Bill Rudman.

Dear Sam,
Keeping any sea animals in a salt water aquarium is not easy because you have to be sure that the amount of "salt" in the water stays constant. You would be best to get advice from an aquarium shop, or look up some books on how to look after a saltwater aquarium.

If you are interested in Sea Hares, which feed on sea weeds, they are probably not so difficult because you can probably feed them on lettuce. Have a look at the messages about Sea Hares .

Nudibranch Sea slugs however, are quite difficult to look after, because they are very fussy feeders, eating only one or two types of food. Their food is usually sponges, hydroids, sea anemones etc, and other colonial animals which are even more difficult than nudibranchs to keep alive in aquaria. It is possible to keep some nudibranchs alive in aquaria for some weeks without feeding them.. but what you are doing then is starving them.

If you are near the sea and would like to keep a few for a day to two to see what they do, then it is quite easy to keep them in fresh sea water without feeding them. But after a day or so you should put them back carefully where you found them. To keep them for a longer time is quite difficult.

Unfortunately our computer cut off your email address. Could you let me know what it is please so I can add it to your message .. Bill Rudman.

Max, I see you are a member of the Uni of NSW diving club. The most experienced group I know of in Australia for keeping Aplysia in captivity are in the University of NSW. Perhaps you should contact Dr Peter Steinberg who has had a number of students working on Aplysia biology over the years, the most recent being Cary Rogers. However the aquarium system they use is hardly domestic. I haven't kept aquaria going for years but as a general rule of thumb you have to start small and not overcrowd. The most important thing is to find what your nudibranchs eat and make sure you have healthy food for them. This is a major problem as true nudibranchs are all carnivores and many feed on difficult to keep alive animals such as hydroids, sponges and ascidians. And most are pretty choosy eating only one or a very few closely related species. Many enthusiasts find that rather then trying to get the food to grow in the aquaria it is best to collect small amounts of food and regularly replace it in the aquaria. As I say often, we know very little about the biology of individual species of nudibranchs and enthusiasts trying to keep animals alive in aquaria is a good way to find at least what they feed on. I am happy to post photos of animals and their food on the Sea Slug Forum as this is a good way to let everyone know of what is often a new bit of information which would otherwise be lost.

I would be interested in a photo or description of the "Pleurobranch" you have seen in schools wandering over the sand. ... Bill Rudman