It depends on the starfish. I feed my green brittle star every day or three. It will eat an entire silverside. I also have a general starfish that will eat silversides. I have to wait until he is on the glass and lift up one of his arms and slide the fish under him. He loves them. He killed and ate my tuxedo urchin, that's how I discovered he needed to be fed. I tried simply leaving a silverside on the sand next to him, but he moved so slowly the snails always got to the fish first.