ok I'm a rookie just started my system. I have a 330 gal tote fish tank, 2  4'x8' media beds, a 16'x4' raft system that serves as a sump tank.  I have about 34 catfish that are 4" to 6".  Problem I have been giving them floating food and they don't seem to be interested.  Is there some trick to get them to eat that food or is it just a wait and see game?