Bob replies...

Hi Gordon,

These small, brown rock anemones are another pest in the aquarium. The sting from their tentacles can cause most corals to close-up and remain closed. Unfortunately they can multiply quickly. I have listed below numerous ways to rid an infested aquarium. Pick the one that best suits your needs;

• If the hobbyist has a fish-only aquarium, they could introduce a Raccoon Butterflyfish (Chaetodon lunula), Klein's (Chaetodon kleinii), the Saddleback (Chaetodon ephippium), Tinker's (Chaetodon tinkeri), the T hreadfin (Chaetodon auriga), or the Copperband (Chaetodon striatus) which will eat these pests. Yet, should there be corals, feather dusters, star polyps or zoanthids in the aquarium, these fish will probably feast on them also.
• I have injected them with boiling water, or very hot Limewater. This causes the anemone to turn a grayish color, effectively killing the entire specimen. Yet, sticking a needle into the anemone before it can withdraw is almost impossible. Lately, I locate a hypodermic syringe filled with hot Limewater about a quarter inch away from the anemone and shoot a stream of hot Limewater upon the anemone. This stuns the anemone and seems to prevent it from withdrawing/shrinking in size. It is then fairly easy to get the point of the needle into the still erect body of the anemone and simply inject it, effectively killing the specimen.
• Another idea recently surfaced is using the sting from an Elegance coral (Catalaphyllia jardinei) to kill the anemone. This does work, as I have tried it!
• Another way to destroy these pest anemones has recently been brought to my attention by a fellow hobbyist in New York. He notes that a slush mixture of sea salt deposited directly on the anemone will cause it to immediately die. Simply take some aquarium sea salt and make a slush-like mixture and flow it directly on the anemone. A syringe is a good way of applying this mixture. It can also be flowed into cracks getting it down to where these pests may have a foot hold.

• The Nudibranch Berghia verrucicornis, native to the Caribbean and western Atlantic, only feeds on Aiptasia anemones. Juveniles measure about 1 cm, with adults reaching 3 cm within a couple of weeks. They are nocturnal. Unfortunately, once these pest anemones are eliminated, the Nudibranch will die because of a lack of food supply. Of course, you can pass it along to a fellow hobbyist who has some of these pest anemones. This way, the Nudibranch may still be available should they return to your aquarium in the future. As of this writing, their availability is scarce.
• A recent biological control is thought to be the Red-legged hermit crab, Dardanus megistos. This small hermit appears to be safe in reef aquarium and is thought to dine on this pest anemone. Yet more than an occasional positive feedback is still needed to confirm its usefullness.
• Another biological control is through the use of Lysmata wurdemanni, usually called the Peppermint Shrimp. This roughly 7 cm shrimp has lengthwise lines of red covering a somewhat transparent body. It does not have claws like the Banded Coral Shrimp, however is an effective killer of Aiptasia anemones. However, they appear to also consume Yellow polyp anemones and zoanthuses. I've used them and they do eliminate any and all Aiptasia anemones!
• Scats (Scatophagidae), which are a brackish and/or freshwater fish, are also a very good consumer of Aiptasia anemones. They not only take a wide variety of foodstuffs, including copious amounts of vegetable matter, they also like these rock anemones. Scats must first be slowly acclimated to seawater for a couple of days before being introduced into reef aquariums.
• Another possible solution is the use of a little known Filefish, Acreichthys tomentosus. It is said to reef safe, yet most filefish are far from reef safe. Caution is advised.
• Novel approaches such as the use of peppery hot sauce is not recommended, nor are chemicals such as hydrogen peroxide, hydrochloride acid or copper compounds.

Hope this helps,

Bob