I've set up a nano macro tank to grow out some algae for the 200 gallon tank. We picked up some true live rock and it came with this little guy. Looks like an asterina to me. I've seen anecdotes of some specimens munching on corals, but very few reports about their interactions with macro. He's about the size of a dime. If they don't pose a danger to the macro, we may just let them proliferate so we can have a harlequin at some point. Would love any insight or information you guys have!