Found a starfish

[Eyford01]

Definitely an asterina, I purposely went out looking for these neat lil hitchhikers, if it's on the glass it is most likely an algae eating variety, from what I've read the algae eaters only go after corals if their numbers exceed the available food (plague proportions) but they're easy enough to just pick out if you feel you have too many, I have never had any sort of a problem with them and would recommend keeping it, congrats!