I used to target feed my serpent star by putting a piece of a frozen food cube in the sand close to the star. The star would goto the food, and take in the whole chunk in one "swallow". cool to watch.
But, I've grown lazy, and havent target fed it since last summer, so I'm not sure what it eats. scavenges I guess. but I still see it every day, and looks as healthy as the first day I got it