Are you sure its not eating the algea sheets while you are not around? My fish tear up algea sheets but because the clip is on the glass right next to me they don't come right up and eat it while I am standing there (well some do, but not the shy ones). Is there any pieces of the algea sheet taken off the following day? I bet the little guy is eating while you are not around, if not I would consider catching it and putting it in a QT tank and working with it in there. It is much easier to get a fish to eat when it is all by itself and comfortable in its surroundings.