Anenome
 

I've got a bright pink one very similar to your green one

I've got a bright pink one very similar to your green one

?
 

it is a rock or flower anemone-i have 2 in my tank-harmless and do not spread like aptasia

http://www.youtube.com/watch?v=8DYu4oPOB0s

video of it closing.

+1 for monocus. Rock anemone. If my aiptaisa looked like that i would be trying to make them multiply not pulling my hair out trying to get rid of them.

rock anemone:)

I will 2nd that, tho im not battling any sort of pest problem apart from my wallet always magically emptying and a girlfriend that wants to upgrade to get something "cool, like the leopard eel"