The Salt Mix: Dealing with Aiptasia, the Prolific Pest Anemone

Author: James Fatherree, MSc

There are over a dozen species of relatively small anemones belonging to the genus Aiptasia, all of which are considered pests in reef aquariums. Commonly known as rock or glass anemones, these may enter the aquarium as hitchhikers on live rock and coral specimens. They can reproduce quickly, which might not sound like a problem at all. However, these small anemones can sting many other cnidarians, including soft and stony corals, leading to tissue damage, and sometimes death. They are also apt at stinging the mantles of colorful Tridacna clams.

You don't want these in your reef aquarium, and I'll tell you how to get rid of them if they show up. Before we approach this issue, a brief overview of the anemone’s biology will provide a solid understanding of the subtleties of this creature.

The Anemones

Aiptasia anemones are relatively small compared to what you'll usually see for sale in stores, as they're typically less than an inch or two in height and diameter with their tentacles outstretched. They also range in color from transparent to opaque brown, with most being a rather transparent light brown. So, you can oftentimes see into their bodies, if not all the way through parts of them, which I assume is where the moniker “glass anemone” originated.

Zooxanthellae

The anemones' brown color comes from symbiotic algae (zooxanthellae) in their bodies, which are the same algae found in other reef-building corals and anemones. These are the algae that provide such animal hosts with an internally produced supply of food. However, Aiptasia can often be found thriving in areas where the lighting is quite dim. They can also rely heavily on other sources of nutrition, such as eating zooplankton and any sort of meaty or flake foods added to an aquarium. Apparently, they can also take in dissolved nutrients from surrounding waters. It’s not uncommon for aquarists to find them growing in an unlit sump, or throughout an overflow.

Reproduction

When they're getting enough of what they need, Aiptasia can quickly reproduce both sexually and asexually, and grow and spread quickly as well. This is a problem, as they have a very strong sting for such small anemones. To make matters worse, they're also resistant to the stings of most other corals. So, they tend to get out of control if not dealt with in a timely manner, and can eventually kill off other cnidarian livestock.

Movement

In addition, Aiptasia frequently move about, slowly creeping over surfaces. While on the go, they can also leave tiny bits of themselves stuck here and there on the substrate, which grow into whole anemones. As only small bits are left behind, the parent stays large and fully functional, and able to leave bit after bit after bit behind as it moves about. This is the primary way you can end up with many Aiptasia from one. Take action immediately if you ever find one (or more) in your aquarium.

Methods of Removal

There are various physical, chemical, and biological means of getting rid of Aiptasia, and some work very well while others hardly work at all. Let’s run through some common methods of dealing with them.

Brute Force

What would seem to be the most obvious—and easiest—way to get rid of these is to cut, scrape, or grind them off the substrate and remove whatever you can. However, I assure you that even grinding them into mush won't completely eradicate them. Remember that reproduction requires only a little tissue from a parent's base to make a new anemone. Even a tiny speck that you might miss will likely survive and recover.

Don't bother with any of these methods, as you'll most likely end up trying again and again without reaching the desired effect. However, if you're only dealing with one, or a few, it is possible to cover them entirely with cyanoacrylate glue or reef-safe epoxy while they are in a hole and seal them in.

Boiling Or Bleaching

In the event that things get out of hand, you may need to remove a whole rock from the aquarium and try something more drastic. You can boil or bleach infested rocks, which will most certainly kill Aiptasia, although it'll also kill anything else on the rock along with them. However, I prefer not to use bleach on rocks: I always worry that a little bleach will be left behind in the holes and pores in the rock, eventually making its way into the aquarium.

Injections

On the other hand, you can try injecting them with various solutions if you're only dealing with one or a few. Using a syringe to inject concentrated lemon juice, hydrogen peroxide, a strong kalkwasser (lime water) mix, or a variety of specialized commercial kalkwasser products directly into Aiptasia can be effective.

However, the problem with any of these is the method of delivery, as Aiptasia typically won't just sit still and allow you to inject them. Many take residence in holes and cracks, and can quickly withdraw into them when bothered. You can end up just sticking the needle into the hole, giving a squirt or two, and hoping for the best. Sometimes it works well, but many times it doesn't, especially when dealing with very small individuals.

Several years ago, a device was introduced on the market that uses a mild electrical discharge to kill Aiptasia. The device plugs into an electrical outlet and acts as a wand, with a syringe tip connected to a handheld controller. When the syringe is placed directly in the center of an Aiptasia’s central disk, it quickly melts them away. While the device does work, often the anemones will retreat into a rock crevice, making it tough to get to them. Also, if you have a massive infestation, using this device can be very time-consuming.

Angels and Nudibranchs

On the other hand, there are several species of fish that often dine on Aiptasia. Unfortunately, almost all of these same fish are also known to eat corals, sponges, and other invertebrate life. Among these are a few of the angels, such as the queen angel (Holacanthus ciliaris). Several butterflyfish—including the yellow longnose butterflies (Forcipiger spp.), the raccoon butterfly (Chaetodon lunula), the teardrop butterfly (Chaetodon unimaculata), the threadfin/auriga butterfly (Chaetodon auriga), and the copperband butterfly (Chelmon rostratus)—are also consumers of Aiptasia.

Of these, the copperband butterfly is the most reasonable option, as this species oftentimes fares well in reef aquariums and will typically eat Aiptasia without causing any collateral damage. They're still not 100-percent safe though, as occasional individuals do become problematic and begin feeding on other things that you don't want eaten. Sometimes they'll nip at feather duster worms, an occasional clam, and even small-polyped stony corals (albeit that's rather uncommon). The other issue is that, for unknown reasons, some individuals won't eat Aiptasia. Trying to use a fish to get rid of them can be rather hit or miss, may lead to other elements being eaten, and is not a preferred method in my opinion.

Next is a species of nudibranch (sea slug) that eat Aiptasia, which goes by the name Berghia stephanieae. Formerly known as Berghia verrucicornis, this nudibranch will most certainly clean up any Aiptasia in an aquarium, while leaving everything else alone. However, they really do eat nothing but Aiptasia, and will starve to death once all of them are gone. So, if you can get one, it's important to find and remove it when the pest anemones are all gone. Hopefully, you can take one back to a shop or find another hobbyist with an Aiptasia problem to give it to.

Peppermint Shrimp

Next are the peppermint shrimp, which include Lysmata wurdemanni and a few other Lysmata species. Peppermint shrimp will also eat Aiptasia, and are typically not a threat to any other cnidarians in an aquarium. While I've read stories of them picking on a few corals, especially euphyllids (frogspawn and hammer corals), I think these are most likely not peppermint shrimp.

Peppermint shrimp will also eat pretty much any sort of fish foods, including flakes and pellets. You don't have to worry about starvation once the Aiptasia are gone. You can also keep two or more of these in the same aquarium if you'd like to have several shrimp.

The biggest problem with peppermint shrimp is that they almost always go after Aiptasia, but not always. As was the case with the copperband butterfly, some peppermint shrimp may not perform the job that they were enlisted for. Aside from that, assuming they do go after Aiptasia, they tend to eat smaller ones and try not to tackle larger members. They can still be nice additions to an aquarium though, and again, are very unlikely to harm anything else.

If you decide to get one, or more, do be sure to get the right shrimp. On occasion, I've seen the camel shrimp (Rhynchocinetes durbanensis) also being sold under the common name peppermint shrimp, which isn't reef-safe at all and is probably the culprit in some of the coral-eating stories I've come across. This species does look quite similar to the peppermint shrimp, especially when small, but it tends to have stronger colors. In addition, the camel shrimp also has a relatively large, jagged horn that projects from its head. It's notorious for feeding on various cnidarians, so watch out for it, and make sure you're getting what you think you're getting.

Hermit Crabs

Finally, there's the white-spotted hermit crab (Dardanus megistos). I've had several of these hermits over the years, both in my own aquariums and those of my customers when I had an aquarium maintenance business, and they've always eaten Aiptasia. In fact, I used to put one in every reef aquarium, whether Aiptasia were present or not.

This hermit will also eat various types of algae and any sorts of foods you use for fish, so you don't have to worry about them starving. With few exceptions, they'd leave everything else alone. I have seen them apparently nipping at button polyps and sea mats, but they always seemed to be after the mucous that these soft corals produced rather than their tissues, as I’ve never found any actually damage. Other than that, I did have one several years ago that nibbled on an ivory bush coral (Oculina) that grew from a piece of aquacultured Gulf live rock I had, but that's it.

Really, the biggest issue you may face with the hermit crab is that they can get rather large and have a habit of crawling and climbing all over things. They can annoy corals and other invertebrates at times, but again, I haven't seen them cause any real damage, with the exception of the coral mentioned above. Of course, if you try one and decide you don't want it, or it eventually grows too large for your comfort, they're very easy to remove from an aquarium.

Take Action!

With all of these issues covered, you can understand that all of these methods or animals have some sort of issue with respect to their use as Aiptasia eaters. Injecting them with chemicals may require a fair amount of work and isn't always effective. Adding a new fish to your aquarium may lead to something else being eaten, or the Aiptasia not being eaten. The Berghia nudibranch will starve if not found and removed once its job is done.

Regardless, it's imperative that you decide on something—and take action as quickly as possible—if Aiptasia show up in your aquarium, before they have time to reproduce, spread, and start causing problems.