it depends on the starfish....
the linkia that was listed above is goign to have an extremly different feeding habit than something like a chocolate chip
I have about six grey serpents and 2 red serpents and they are great for feeding on waste. I never have to feed them directly but they will capture food that I put in for the fish.
only some brittle stars, like the Green death star, eat fish not all.
and like fishieness said we need to know what kind it is. and if u dont know urself just post a pick and well help out.
most starfish will eat any fish they are able to catch. but this is pretty rare unless the fish is sickor a super heavy sleeper. lol. as with all echinoderms, starfish do not have a true brain, therefore,they dont really know ifwhat they are eating is a piece of krill off of a stick or a live fish. as most things in the ocean, they are opportunistic feeders, taking what they can get.
but yes, as german man said, the green's seem to have the worse reputation with this, probably because of their large size.
they also have a very low survival rate because unless you have a large tank with a very deep sand bed, there is usualy never enough macrofauna for the starfish to eat, so they starve.