Finally setup a tank a couple days back and found a two of these guys on live rock. From my reading I thought they could possibly be Aiptasia since they seem to be common hitchhikers. Each is aprox 1 inch diameter and the centers fluoresce green under blue light Thought I'd get some pro opinions than this noobs view. So kill the critters or live and let live?
On a good note, did find some nice Colt coral that came for a ride!