os ther algae in the tank? if not he should have a constant supply of something to graze on, they do this all day in the wild.Try giving him pieces of fruits and veggise to find out what he likes (and what the other fsh like) then vary the diet to include what any of the fish seem to like and what he likes at least once a week. the algae tabs will help, just don't use prepared foods as the only source of nutrition personally, my fish get fed flaes as a staple, and then brine shrimp table shrimp and any other veggie/fruit item I may happen to have at the moment. the only things you need to remember are no seasoning, always rinse any veggies or fruits well before feeding to fish(you don't want pesticides in the tank do you?) and don't leave anything in the tank for more than 24 hours.