From FrugalReef

Aiptasia is considered a pest. It is very hardy, breeds prolifically, and will take over a reef tank in next to no time. These tiny anemones will spawn if you damage them, and any pieces that flow away may attach and grow a new specimen. Many chemical concoctions are available to deal with this problem, but by and large it's usually not difficult to find something that will eat them. Hermit Crabs and Peppermint Shrimp are two common aquarium inhabitants that will do them in. In particular, Mexican and red legged hermit crabs are said to be effective.

[edit] See Also

• http://www.wetwebmedia.com/marine/inverts/cnidaria/anthozoa/aiptasia/aiptasia.htm