What does your copperband butterfly eat?

I've had mine for a week and have yet to see him eat. He (Gilligan) doesn't even pick at rocks. I've tried mysis, brine and pellets. No go. Tommorow I'm going to drive 30 miles to get him a clam. Yes, a 60 mile round trip for a clam. Our seafood market on the dock was swept into the ocean during our last storm. But that's beside the point. If you have one, what does it eat?