You can feed them a little microvert which is designed for filter feeders and corals. (it is ok for freshwater shrimp, freshwater clams, mussels etc.) also, they will move around the tank picking up scraps off the bottom. Some seem to prefer doing this to hanging out in a current and fanning. I've watched them closely and I think they stick pretty much anything they catch with their baseball mitts into their mouths. It all goes through -- one I saw last night had a three inch string of poop hanging from his rear end. He was clinging to the filter like another poster mentioned which they like to do. If you like them get some "vampire" shrimp (Atya gabonensis) if you can find them -- they will all live happily together with RCS and well mannered fish.