Help identify this hitchhiker: translucent tentacled organism on live rock

[bardia]

Hi all,

I recently noticed a small hitchhiker on my live rock and I can’t figure out what it is. It’s about a quarter inch across and mostly translucent. When the lights are low, it extends a ring of tiny tentacles, but it retracts quickly if I bump the rock or shine a light on it. Does this sound like some kind of harmless filter feeder, or could it be a pest? I’m curious whether anyone has seen something like this in their reefs and whether I should leave it alone or remove it. Thanks for any insight!

 

[dball711]

Can you get a picture?

 

[Arielneedscoralsanon]

Is it possibly a ball anemone? Sounds similar to a few guys that have popped up in my tank. The tentacles are like little tiny green balls in a ring when it’s out and that’s all you can really see. I’ll see if I can snap a pic sometime today if it shows itself, please do the same with yours!