are these the ones that look like brittle stars? if so, they are definitely not
eating the corals. they are just using them as hiding places.
if these are asterinas that are definitely eating coral, then you can buy a harlequin shrimp. this shrimp will eat them, but it must have a steady diet of starfish. this is the only thing on the menu for the harlequin shrimp. after the starfish are gone, you'll have to either get rid of it, or buy it starfish to eat.
i would only suggest a harlequin shrimp if you have a serious infestation of starfish, like this 40 breeder i used to have-