my LFS told me they eat phytoplankton in the water by using the "feather duster" part of it to act as a filter and catch the food in them. they sold me frozen zooplankton made by cyclopeeze(something like that) and said to just feed it a little bit every few days or so by releasing it near the feather duster, or using a turkey baster to target feed directly into it. I've just been releasing small amounts of the food near the duster like once or twice a week and he seems to be doing just fine. I'll be interested to see what others have to say though, and find out if what the LFS told me was correct.