Aquarium Pests: Anemones (Majanos, Aiptasia, etc)

At some point or another, you’ll be shining a flashlight onto your aquarium at 3am to find out what is eating your prized coral.  We all dread it, but it is better to be prepared than to try to identify the creature at what is now…oh…say 4am after you pulled it out along with all of your rock.

The “Aquarium Pests” column will feature various aquarium pests and the most current methods of eradication.  Although it is often hard to identify down to the species level in home aquaria, “close enough” will usually suffice.

The most common pest anemones are Aiptasia and Majano anemones.  Orange Ball Anemones (Psuedocorynactis) are not actually anemones, so they will not be discussed here.  However, they can be eradicated as pest anemones would be (see below).  Aiptasia is of the phylum Cnidaria, class Anthozoa, order Actiniaria, family Aiptasiidae, and genus Aiptasia.  Generally the two most common Aiptasia species found in the aquarium hobby are A. pallida and A. pulchella.

Anemones consist of a pedal disk, an oral disk, and a complete digestive system.  Around the oral disk are many tentacles which contain stinging cells, called nematocysts.  The tentacles help catch the prey, the stinging cells help immobilize the prey, and then the tentacles move the prey to the oral disk into the digestive system.  Although some anemones may be beautiful (like the Majano below in green and pink), Aiptasia is generally brown to brownish-green in color.

Majano Anemone
Pest anemones can thrive under a variety of conditions that desirable anemones (or anything for that matter) typically cannot.  They thrive in high light, high nutrient systems, but they may also live in low light and low nutrient systems.  Unfortunately, they are also capable of reproducing sexually and asexually.
Eradication of pest anemones consists of several methods:  prevention, natural predation, and chemical methods.
To prevent an infestation of anemones, it is important to quarantine all new inhabitants for at least one month, preferably two.  After quarantine, the liklihood of anemones appearing can be further diminished by maintaining a low nutrient system.
Using natural predators on anemones is highly controversial since some predators may perish shortly after exhausting the food supply.  However, natural predation may be the only recourse for large infestations.  Common predators are certain butterfly fish, true peppermint shrimp (not camel shrimp), the Berghia nudibranch, and sometimes even puffers.  Although these animals have been known to prey on anemones, they are not a guarantee.  They also may eat other inhabitants of the aquarium, such as corals and/or other invertebrates.
Chemical preparations tend to be the most effective means of eradication for small infestations other than complete prevention.  Some common chemicals are listed:  sodium hydroxide, vinegar (or lemon juice), kalkwasser paste, boiling reverse osmosis water, “Joe’s Juice”, and other commercially available brands.  Before using a chemical solution on the anemone, I always purposefully target feed it one last big meal.  This causes the anemone to expand to where it cannot retract back into its hole.  After donning proper safety gear (such as chemical goggles and non-powdered gloves) a syringe of some description is filled with the recommended doseage (do not mix the above stated solutions as unknown chemical reactions may occur.)  The needle is then inserted into the middle of the oral disk of the anemone, and the plunger is pushed, expelling the solution into the digestive system of the anemone.  Sodium hydroxide, which may be obtained at local chemical supply stores, seems to be the most effective, which a kill rate of approximately 90%.  Although many liquid plumbing gels contain sodium hydroxide, they are highly not recommended as a substitute for sodium hydroxide.  It is also important to keep in mind that most chemicals are very caustic, especially sodium hydroxide.  Keep this, and all chemicals, out of the reach of pets, children, and off skin and clothing.
If eradication does not work, some aquarists have resorted to an “anemone scrubbing” refugium since they are effective at processing excess nutrients.  Essentially, the refugium is purposefully filled with pest anemones and fed initally in the hopes that they will reproduce in ideal conditions and leave the main tank fairly uninhabited.
Most aquarists do not appreciate Aiptasia or Majano anemones stinging their prized corals (or their bare arms for that matter!)  Although identification is fairly simple, methods for eradication are not 100%.  Prevention is the best solution. 


  1. Patty

    You neglected to mention the Aiptasia eating File fish as a option for eradicating these pests and I was curious to why?

    1. admin

      You’re correct – the Aiptasia-eating File Fish (Acreichthys tomentosus) is another natural predator among many others not covered. I did not cover natural predators in-depth in the article since I prefer and recommend more sustainable/non-controversial and complete methods of treatment. I also need to add the aiptasia lasers to the article since those are increasing in use. Thanks for the addition!

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