The Reefer: The Carpet Anemones

Author: James W. Fatherree, MSc

Sea anemones can be very attractive and interesting additions to an aquarium, and their associations with different species of clownfishes makes them even more desirable to many marine aquarists. The carpet anemones are some of the most impressive species available—they can reach impressive sizes when cared for properly, and they also host a number of clowns.

This month I want to take a look at these anemones in particular, and provide information about caring for them in aquariums, how to choose good specimens, and which clowns fit best with them.

The Basics

Carpet Anemones

There are three different species of carpet anemones typically seen in the hobby. Stichodactyla gigantea, Stichodactyla haddoni, and Stichodactyla mertensii are called carpet anemones because they have large flattened bodies, and their upper surface is covered by numerous relatively short carpet-like tentacles. I’ve seen some of them being sold as “saddle” anemones, as they can sometimes fold their bodies into a shape that looks something like a horse’s saddle. However, of the three species, S. haddoni is seen for sale far more often than either of the other two.

All three of these can be rather difficult to identify at a shop when they’re not in their natural habitat with clownfish living in them. But there are a few tips for how to best identify them.

Stichodactyla haddoni

Stichodactyla haddoni has very small tentacles that typically look like little beads that cover the surface, and they’re often more than one color. There’s only a small area around their mouth that is free of tentacles, too. Additionally, the upper part (disc) is often folded into a saddle-like form, which is where that name comes from. They can grow to about 2 feet in diameter and have a relatively large base, as well. Also note that, when healthy, the tentacles are almost like fly-paper and will stick to your fingers well enough that they’ll tear off a specimen if you touch one.

Stichodactyla gigantea

Stichodactyla gigantea also have short tentacles, but they’re typically a bit longer than those of S. haddoni and are often slightly pointed at their tips. Their disc is usually deeply folded, with more folds than S. haddoni. Typically, much more of the disc is free of tentacles though, and these may grow to “only” 16 inches or so. The tentacles are sticky, as well.

Stichodactyla mertensii

Lastly, Stichodactyla mertensii typically have short tentacles, but some may be relatively long for carpet anemones, as in almost an inch in length. They’re also absent in the area right around the mouth, and they’re non-sticky, unlike those of the other two species. Their base is typically much smaller than that of the other two, and the disc usually doesn’t fold up either. Instead, these lie flat on the substrate, and they’re also the largest of the three, sometimes being over 3 feet across.

Aquarium Care

Anemones in general have a pathetically poor survival rate in aquariums, but some species tend to fare far better than others. Fortunately I’ve had good luck for the most part with carpets, and I think that if you choose a good specimen and know how to care for it properly you’ll greatly increase your chances of success. But when it comes down to it, they can still be rather hit or miss, and if you aren’t prepared to go the distance and provide one with everything it needs then don’t buy one. As you’ll see, having good water quality is important (always is), but lighting, placement, current, and feeding are all very important to consider, as well.

Water Quality

When I say water quality should be good, that means it should be of high enough quality to keep corals and other sensitive invertebrates. Ammonia and nitrite should be near zero, nitrate should be kept at a few parts per million or less, pH should be in the neighborhood of 8 to 8.4, etc. Basically, if you haven’t already mastered maintaining good water quality, I think it’s best to not fool with an anemone (yet).

Lighting

Carpet anemones house symbiotic algae (zooxanthellae) in their tissues, just like reef-dwelling corals do, and thus rely heavily on strong lighting in order to stay healthy. Unfortunately, I’ve come across a surprising number of hobbyists and ignorant (or unscrupulous) store employees that don’t seem to know this.

Like corals, carpet anemones need the symbiotic algae in their bodies in order to survive; they can’t rely strictly on foods you may provide, no matter how much you feed them. They don’t necessarily require a full-blown reef-lighting system with metal halide bulbs, but they’ll need a lot more than just a standard wattage fluorescent tube or two for long-term success.

With all the lighting setups out there to choose from there’s no way I can cover every possible type of light that will work, so I’ll just say that you shouldn’t try to keep a carpet anemone under anything less than what would be required to keep lower-light corals alive and well. In general this would be a minimum of a couple of high-output fluorescent bulbs over a small to medium tank, with more bulbs for larger tanks. If you don’t have enough you’ll get to watch your anemones slowly shrink in size over a period of weeks until they finally die.

Living Space

Carpet anemones can sometimes be picky about where they live, and you should put some thought into where to locate one. This is important, as an unhappy anemone will be an unhealthy anemone, and they can crawl around looking for a better spot if they aren’t pleased with where you place them. This can be a very bad thing, as many immobile tankmates they might come into contact with or cover up can be killed. So you need to try to get the positioning right in the first place.

Of course, you can also put the baserock/liverock and anemone into an aquarium first, let it settle in where it wants to, and then start adding the other things. Fortunately, I’ve found that, once situated, the majority of anemones will stay put indefinitely.

It’s important to note that these three species don’t all live in the same type of place and will prefer their own particular living arrangements.

S. haddoni Dwelling

S. haddoni actually lives in deep sand with its base dug in deeply, which allows it to retract its body into the sand and retreat if bothered. So it’s best to place a specimen on a deep sandbed where it will feel at home. Still, they’re occasionally found on hard substrates too, and you may find that one will attach itself to rocks and such even if initially paced on sand.

S. gigantean Dwelling

S. gigantea is typically found with its base attached to something solid that’s buried in sand so that much of the base is buried, too. But, again, they could also be found attached to hard substrates at the surface. Thus, the best thing to do with either of these anemones is to dig a hole in the sand and place their base in the hole, then fill it in around the base and put a piece of live rock right next to it. This has worked well for me, as the anemone attaches its base to the bottom pane of glass in the tank and then extends its disc over the bottom and the rock.

S. mertensii Dwelling

Conversely, S. mertensii typically lives on hard substrates with its base attached in a crevice or hole and its disc held close to the surrounding rocks, therefore it’s best to arrange the rocks in such a way that it can do the same in a tank. Place a specimen with its base in the crevice/hole and let it make its attachment there.

If the lighting and current are acceptable (and remain that way) the anemone will usually stay put. They’ll need some flow over them. You don’t want a current hitting one from one direction with enough strength to constantly flip over part of its disc and keep it folded up—that will get one moving for sure.

Feeding

The next thing to take into consideration is feeding. Carpet anemones are definitely carnivores and should be treated as such. A good meal once or twice a week is usually plenty to keep them healthy and growing. You certainly don’t have to give them something to eat every day, but you should experiment with different types of meaty foods to find out what and how much they’ll eat. To do so, you can give them food using anything from a turkey baster to squirt some brine shrimp into the tentacles, to a wooden stick (or your hand) to deliver a small fish. Just watch out for nasty looking balls of goop that they may spit out if being fed too much at one time.

In general, you’ll find that carpet anemones can be absolute hogs. They’ll usually eat anything made of flesh, including brine shrimp, clam meat, whole shrimps, and feeder fishes like goldfish and guppies. I used to feed mine twice a week, but eventually I had to back off, as it quickly grew to 12 inches in diameter and eventually reached about 20 inches. That’ll take up a lot of room in a tank! Basically, you should keep an eye on a carpet anemone’s size, and if it starts to shrink then you need to be feeding more (and/or giving it more light).

Shopping

Again, starting with a good specimen is a must if you expect to be successful, so here are a few shopping tips for you. First, any anemone should be firmly attached to something at the shop, as in a rock, shell, the glass, etc. If its base is just puckered up and it’s not holding onto anything, and the anemone is just sitting on the bottom, I’d pass it up.

This doesn’t mean that you have to take it home attached to something, but rather the attachment to something is usually a sign of good health in itself. You do need to make absolutely sure that a store employee is extremely careful when removing an anemone from whatever it’s attached to. If a specimen is attached to something smooth, it can usually be removed easily and safely using a credit card, but is much more difficult if it’s stuck on a rock. Peeling the anemone off can still be done, of course, but it can also just be left on the rock.

Check Your Anemone

Before getting to the removal, you should first give an anemone a good looking over to make sure that it doesn’t have any obvious injuries. They can hold onto a rock very well, so they can often get tears or cuts on their bases during the collection process when someone has to get them loose. Any such injuries can lead to quick death—or to an infection and a postponed demise.

Another important thing to look for is a closed mouth. A carpet anemone’s mouth is usually easy enough to spot, being right in the middle of its disc. It should not be gaping open. If a specimen’s mouth is opened up for no apparent reason (and especially if any of the “guts” are protruding from the mouth) you should not purchase it. A gaping mouth is generally a good indication that an anemone is on the way out.

Bleaching

Other than that, about the only other thing to watch out for is a bleached specimen. Bleaching occurs primarily when an anemone, coral, giant clam, etc. is exposed to elevated temperatures that get too high for too long. The result is the expulsion of the animal’s complement of zooxanthellae, which eventually leaves the host looking very pale to white, or even translucent. This is not good, as many bleached animals don’t recover. Thus, you should also refrain from buying a specimen that lacks color.

Matching Clownfish

A carpet anemone‘s tentacles are covered by numerous stinging cells called cnidocytes, and these cells fire tiny harpoon-like structures into prey when contact is made. These structures can then allow an anemone to hold on to a prey item and also inject venom into the victim in order to immobilize or kill it. However, they don‘t sting everything they touch. The tentacles and their stinging cells do not react to random brushes with rocks, sand, and other non-fleshy items in their surroundings, and they don’t react to contact with certain clownfish either. Basically the anemones don’t recognize these things as “meat.” So a clownfish can swim right into an anemone without being grabbed and stung to death.

However, each species of anemone will only host specific types of clownfish, and if the wrong species of clown were to attempt to enter the wrong species of anemone, it will most likely be treated just like any other prey and be stung. Oddly enough, the species matchups are often more flexible in aquariums than they are in the wild. For whatever reason, matchups not observed in the wild are sometimes encountered in tanks, and it seems that when no “normal” host anemone is present, some clowns will make due with something else.

Clownfish Tankmates

The carpet anemones can be called home by quite a few of the commonly offered clownfish species, including the clarkii clown, the pink skunk clown, the percula clown, the false percula clown, and many others. To be specific, S. haddoni hosts Amphiprion akindynos, A. chrysogaster, A. chrysopterus, A. clarkii, A. polymnus, and A. sebae. On the other hand, S. gigantea hosts A. akindynos, A. bicinctus, A. clarkii, A. Amphiprion, A. ocellaris, A. percula, A. perideraion, and A. rubrocinctus. The less common S. mertensii hosts A. akallopisos, A. akindynos, A. allardi, A. chrysogaster, A. chrysopterus, A. clarkii, A. fuscocaudatus, A. latifasciatus, A. leucokranos, A. ocellaris, A. sandaracinos, and A. tricinctus.

Inconsistencies

As you can see, there are plenty of matchups that can be tried. However, I’ve experienced some inconsistencies with these anemones, and I wouldn’t absolutely guarantee any of these matchups except for A. clarkii due to the fact that on a couple of occasions I‘ve seen some of these clowns ignore a supposedly compatible carpet—even when it was the only anemone in the tank. To the contrary, I have never once seen a clarkii clown reject a carpet anemone, or vice versa (or any other host species of anemone for that matter), which is a shame in many cases, as this particular species of clown can get relatively large and often has a bad attitude.

One Last Thing

Keep in mind that carpet anemones can really pack a punch and can kill most anything they come into contact with in an aquarium. So it’s best to get one situated in the tank before adding any other livestock that would likely be killed if the anemone should start to crawl around. Be sure to leave quite a few inches of space around the area where they settle so they’ll have some growing room, too. And I hate to say it, but even if you do everything right and keep it well fed, a carpet anemone will very likely end up eating any sort of bottom-dwelling fishes (like gobies and blennies, etc.) and other things you might think about keeping with it.

My Moving Dilemma

For example, I had a huge carpet anemone in my 150-gallon tank for several years, and over that time it managed to nab several snails, a spiny sea urchin (yep, spines and all), and about 10 fishes. I should have moved it out of there early on, but it grew so large and looked so good where it was that I just couldn’t do it.

However, when it came time for a big move a few states away, I had to break down my tanks and pack them up. So I got to start over with everything and ended up setting up a 56-gallon “tub” tank specifically for the anemone and the pair of clarkii clowns that had lived in it for about seven years. There were no other fishes in the tank with the exception of a few damsels (cheap and easy to replace), and the tank was topped by a single metal halide pendant. It was perfect (right up until I had to move again a couple of years later and lost it during the move, probably due to overheating, which I unfortunately couldn’t avoid at the time).

The point is, if you plan on keeping a carpet anemone, be prepared for losses unless you keep it alone or with a compatible species of clownfish. Really, that’s the best thing to plan on doing anyway. Keep them in their own dedicated tank with as few non-clownfishes as you can stand.

See the full article on TFH Digital http://www.tfhdigital.com/tfh/200710/#pg76