Amazing animals, I had a pair of them. They do not fight with anyone else in the tank and mind their own business. Do not keep them with wrasse as the fish will eat them, hence why I say had!
They will eat any kind of star fish and their predatory skills are amazing, drop a star in one side of the tank with them on the other and they almost instantly know. Best SF to feed them are Choc chips as they retain their shape and dont dissolve as easy as other stars. Usually took a week for a full size choc chip to be eaten by my pair.