I've been in this hobby on and off for 15 years and hardcore for about 5 now, and this is a new one on me. LFS got 3 feather stars in last night. Very beautiful and interesting creature, but I didn't want to spend $80 of something I knew nothing about. What are their requirements, reef safe, etc. etc.

Yes, Ron has a great article on feather stars (Comatulid crinoids) in the Aquarium.Net archives ( http://www.aquarium.net/1296/1296_9.shtml ), and I suggest that you read it if you have any serious interest in keeping these fascinating animals. In that article he explains that crinoids are even more difficult to feed than the majority of filter feeders, because they have a very specific feeding mode that requires a lot of suspended planktonic food of a certain size range. Although the requirement for suspended particluate food of a given size range is generally true of other filter feeders as well, most filter-feeders capture everything that passes through their filtering apparatus (passive capture) that is approximately the correct size (there are no "taste" receptors on the filtering sturctures) and transport it to the mouth where the particles are sorted, and the "tasty" ones are ingested, while the undesirable particles are ejected a "pseudofeces." Even desirable particles can be ejected this way (in balls of mucus) if the suspended particle load is too high, and the animals are capturing more than they can consume. Fortunately for us (and for them :) ) most typically become less selective the more hungry they get -- so animals like fan worms and clams will usually end up eating whichever particles are available, even if they would ignore these same foods in the wild (this has been demonstrated in a number of captive feeding experiments with a wide range of animals).

Unfortunately for us (and for the feather stars) they filter particles actively, by selecting the "tasty" particles from the water before they capture them. That means that they don't even capture foods that they do not want, and even worse, their food preferences seem to be "hard-wired" on the basis of size, weight, flavor or some combination of those factors. What I mean by that is they only respond to the tasty food items that they would normally take in the wild, and do not appear to show the same decreasing selectivity response when they get hungry that many other filter feeders do. That means that you need to be able to provide a natural diet for the animals in order for them to have *any* chance of surviving in your tank.

So what is the natural diet? Well, this turns out to be a big probelm as well -- first, there haven't been detailed studies of a lot of species, so we're forced to assume (and hope) that the rest of the animals do the same things as the ones that are studied. Unfortunately, despite the fact that there about 400 species of these animals, and they can often be quite abundant in certain areas, they are poorly studied and we don't really know how general the patterns seen in the few studied cases are. With a bit of luck, though, the species in your LFS has the same preference for very small zooplankton, invertebrate larvae, ciliates (and other protozoans), and large phytoplankton (such as concentric diatoms) as the few species that have been studied. If the animal recognizes these same prey items, there is at least a chance of providing food for it, if not, your guess for providing food for it is as good as mine :(

Despite all those problems, it *is* possible to keep one of these animals in an aquarium -- I must admit that I have one (Himerometra). However, I must also admit that I consider myself an above average aquarist, and I have constant access to foods (such as invertebrate larvae) that few aquarists would. Despite that, I am not currently providing my star with any of those foods -- it's is surviving (and regrowing all the arms damaged during shipment) in my refugium sump. The animal has attached itself to the "spraybar" the delivers water from the tank to the sump, and simply spreads it's arms into the flow generated from that. This tank has a sandbed in the aquarium, as well as one in the sump, there is also an in-tank refugium (from Inland Aquatics) complete with thier detritivore kits and live sand, and the sump was stocked with live sand that I collected myself in various places. I have a *lot* of sand fauna and there is a constant supply of worm larvae, rotifers and protozoans in the aquarium from those sources. In addition, I feed the tank heavily with enriched brine nauplii and phytoplankton (among other things), and also feed rotifers, copepod and various invertebrate larval cultures when I have excess. I have not had the star for very long, but it has shown significant growth in the time that I have had it, so I suspect that it will do fine -- of course, I'm prepared to start specifically target feeding it invertebrate larvae in a separate container if the animal shows signs that it is not getting enough food at some point.

There was recently a post on another list about just this sort of message -- it went something like this:

John Doe,

I think your one failing, if you could call it that, is that you are an advanced hobbiest. Advanced hobbiests can keep difficult critters in some cases, but they are only a very small fraction of the "aquarium world." Perhaps.

Since my move to Houston, I've had the pleasure of interacting w/ hobbiests much more advanced than myself, (>10 yrs exp.) and I've learned one thing that I would like to share. When advanced hobbiests share the fact that they can keep goniopora, cleaner wrasses, regal angels, etc..., they only hurt the hobby at large. When you say that you can keep a cleaner wrasse, others will try it - they think of you as an advanced hobbiest after all. What they might now know is that you have a 450g tank with a lot of fish in it.

Believe me, I am not trying to flame you at all. I'm just airing a frustration that I have w/ the hobby in general. Every time someone starts a goniopora thread, about how there have a <1% success rate, there is always someone who chimes in that they have been keeping them for 2 yrs. Well, I say, "Yeah, thanks a lot buddy! That is so helpful! Do you know why you are successful?" Well....No...

It may give you satisfaction to keep cleaner wrasses and other difficult animals, and it may also give you satisfaction to post your experiences about it. While I agree that it may be all right to do the former, I don't think it helps the hobby to do the latter.

I think that this post really makes an important point -- there are many people on the Net that like to post about their success with difficult species. While it is difficult to determine how many of those posts are true, even if they were all accurate, I still agree with original poster of the letter above that simply boasting of success is not helpful at all, and in fact may be unltimately detrimental to the hobby. I enjoy trying to push myself and see if I can keep difficult animals, but I do *not* encourage others to do it (as I'm sure you'll realize if you've read any of my posts in response to information requests on other difficult species), but if someone is determined to try, I will try to porvide them with the information required to give them the greatest chance of success. There will always be people who want to push the envelope, and if they succeed and can figure out why and how, that helps everyone else who would like to keep those animals -- that's how the hobby advances. The last paragraph of the letter above reads a little harshly, but I suspect that the intention of the author was along the same lines -- a short response saying "I've had lots of success keeping Dendronephthya" (or Goniopora or whatever difficult species you choose) is harmful rather than helpful to both the animals and the person asking for help, because the vast majority of people not only fail to repeat that success but typically get discouraged by the failure. I hope that people realize that when I provide the biology for animals in my post, I am trying to give you the background necessary to make these sort of decisions about your setup, your ability, and the likelihood of success on your own -- I can discourage you from getting the animal and give you all the reasons to stay away from it, but the ultimate decision on whether or not you'll buy it still lies with you....

When you say 'invertebrate larvae', are you meaning the cryopastes from various suppliers?

Nope, the cryopastes are the same as DTs: they are phytoplankton (aka greenwater or tiny algae). "Invertebrate" is a catch-all term for "anything that isn't a vertebrate." This is an archaic carry-over from the traditional split between the enormous number of folks who study vertebrates (hence the subdisciplines of ornithology-birds, herpetology-reptiles&hibians, mammology-mammals, ichthyology-fishes) and the few weirdos who studied snotty, mushy things (about 98% of animal diversity that represent all the higher taxonomic diversity on the planet, but get lumped together into 1 discipline -- invertebrate zoology).

Invertebrate larvae are the (typically) microscopic juveniles that are released by about 80% of all marine animals and which spend some variable amount of time (from minutes to months) swimming in the ocean currents before they are capable of metamorphosing into the adult body form (like a caterpillar metamorphosing into a butterfly). There are no commercially available sources of invertebrate larvae for the average hobbyist (there *are* larvae that are commercially available -- such as oyster, abalone and trochus -- but they're so expensive that it would be impossible to use them as a food source). There is a picture of a polychaete larva (Phragmatopoma) at http://www.aquarium.net/0897/0897_5.shtml , and there are pictures of a variety of the other prey these stars like in Ron's article It's (in) the water at http://www.aquarium.net/0997/0997_4.shtml . Unless you're close to the coast and have the luxury of collecting egg masses to culture for feeding or keeping a tank full of IPSF's "sea bunnies" to continually produce larvae for you, you're unlikely to have enough larvae to feed a predator such as this...

One thing that was strange is that these guys could withstand quite an amount of flow and secondly that they didn't get covered by algae? Any suggestions why Rob? What are your sources for invert larvae? Did you just have some tanks with coepods or amphipods that you remove the water from at night once a week? Or are these bred for food for creatures such as jellies? Or attempting to raise other marine organisms?

I was originally thinking of trying an animal in the main tank. The reason that I decided to put mine in the sump was:

1. I was worried about it latching directly onto the highest point with flow in my display tank (which will undoubtedly be my Hydnophora colony)
2. I figured that it could filter everything from the tank that came down the overflow if I set a rock directly in front of the overflow line.

The star decided "directly in front of" wasn't close enough, and promptly crawled onto the spray bar where it has remained ever since and seems to be doing just fine there. I think you're right, in retrospect, this may actually be the best choice to keep it.

As for the problem with algae -- many marine animals spend a fair bit of energy in maintaining defenses against being "fouled" (having algae or other invertebrates settle and grow on them). Feather stars are no exception, and if the animal is unable to prevent algal growth, then it is obviously sick. I think that the warning is actually more likely to be about their entanglement in Caulerpa, which is (although a relatively poor choice) the most likely alga for most people to have in a refugium or sump. Feather stars feed by slowly waving their arms back and forth in a graceful, almost dance-like motion. Because they are so spiny and relatively clumsy, it is easy for them to become entangled in the long stringy bits of macroalgae and therefore not be able to fed, even if there is a surplus of acceptable food available.

As for larvae, yes to all of those. I'm a larval biologist, so we almost always have cultures of corals, hydroids, snails, nudibranchs or worms going in some form or another in the lab. I also raise a lot of rotifers and copepods to feed to my baby seahorses and to my pipefish, and we also culture a variety of these animals to feed to the jellies and ctenophores that I keep.

I also wanted to clarify my statements about difficult to keep species above. I certainly do not mean that no one should talk about keeping Goniopora, Dendronephthya, feather stars or any other difficult animal -- what I was trying to say is that when someone (like Fox in this case) asks about a difficult animal, posting a couple of sentences saying, "Yep, I've done it. My feather star lives in my sump." doesn't give an indication that it is difficult or why. If I had posted something like that, I suspect the impression it would leave would be that Fox should try it as well. Chances are that attempt would have been unsuccessful because there was no exchange of information, simply my boasting of my success. It is those sort of posts that I think are harmful, because it both encourages the person asking the question to try (Hey, others are doing it, I should be able to as well, right?), and ensures their failure (because they haven't been given any information about how to keep the animal, why it's difficult, or what the chance of success are). If you're posting the information and explaining the difficulties involved and why you think you're having success with the animal, I think it's a good thing, because it gives the original poster a chance to make up their own mind, and if your advice and explanation work, then that person may succeed. That's how we learn to keep new animals in the hobby. Does that make more sense?

I can't remember who asked about feather stars (Comatulid crinoids), but I thought I'd try to answer it (better late than never, right?) ....... edited out same first five paragraphs as above ....

One additional consideration with these animals is that they do poorly in a tank with a lot of macroalgae -- many marine animals spend a fair bit of energy in maintaining defenses against being "fouled" (having algae or other invertebrates settle and grow on them) Feather stars are no exception, and if the animal is unable to prevent algal growth, then it is obviously sick In this case, however, there is more to consider than simply fouling -- feather stars feed by slowly waving their arms back and forth in a graceful, almost dance-like motion. Because they are so spiny and relatively clumsy, it is easy for them to become entangled in the long stringy bits of macroalgae and therefore not be able to fed, even if there is a surplus of acceptable food available. Hence, dense growth of macroalgae in an aquarium housing one of these animals should be considered a no-no.

There are no known specific chemical defenses of the type associated with sponges, tunicates or sea cucumbers known for the Comatulids. These animals are thought to defend themselves by being more-or-less useless food items -- they have only a thin veneer of live tissue around their carbonate skeleton, and for most animals, the energy gain from eating them is lower than the energy expended in finding and consuming them, so they are rarely included in the diet of predatory species. The tank wipe-out from the introduction of one of these animals is the first of which I've heard, and I can't even guess at what happened, although the possibility that it was a stress-induced spawn that snowballed is as likely as any explanation.