What kind of starfish is this?

IMHO asterina stars are NOT reef safe, allways try and pull them out when you see them just to be safe. I was raising some tunicates that came in some LR from a LFS when i had noticed a wierd outbreak of these guys. A couple days later my tunicate colony was gone along with some really small kenya frags in the ame area...

 

ive had them for years never had a problem with them and my corals. i all ways watch close i even use a magnifying glass. i love checking of the micro stuff

 

If you have a big colony get some bongo shrimp. They look pretty cool and I think they prey on these things. You want a conversation piece, have them attack the stars while people are watching.

 

Keep them I say. Unless you see them consistently on coral they are good. Even if you see one on coral, don't throw it out immediately. It may just have wandered onto the coral and it could just be eating algae off the coral. Only get rid of it if its consistently on there.