What they actually do is eat a lot of the little worms and critters living in the sand. That is their primary diet...some may, some may not, take to additional food. How long have you had it? Typically in smaller tanks, say 55g and under, they starve in 8-12 months or so (they literally start to disintegrate). In larger tanks, it may take longer, or they may survive...so long as it is only one star. Additional one's mean competition. Very tough call to make on the minimum tank size. But if you put a small piece of shrimp in front of it, or put the shrimp on a bamboo skewer and kind of place it next to the arm...the star may feed on that. This is "spot feeding." It is basically just insuring that they get their fair share of food....in our tanks, we tend to have a lot of "clean up" critters and some that need more food may not get enough.
