Aiptasia or zoanthids?

[Spen2cer]

I just got this tank from another owner, and I cant tell what these organisms are. They are green on the outside polyps, with a purple inner circle. They are about 1/4 inch or 1/2 centimeter in diameter.

 

[PheonixKingZ]

I have no clue - @Colin_T and @Chad know a lot about Saltwater/reefs. They may be able to help.

 

[Chad]

Sometimes it can be hard to tell since they are related. From the photo this looks to me like it is a majano anemone. Coloration and the rounded shape of the tentacles are identifiers.

The majano is also a pest and has a strong sting. How to take care of them depends on what else you have in the tank. Generally you create a paste of calcium hydroxide (pickling lime) commonly called Kalk in the hobby after the German term Kalkwasser, and cover the mouth with it.