All posts regarding the care and breeding of catfishes from other parts of the world (North America, Europe and Australia). If you don't know where your catfish is from, post a query in the identification category.
I would say lose the feeder fish (maybe that's what gave it the disease in the first place) and just go with cicklid sticks or some other compressed (pelleted) fish food (it would be good if you can get your hands on trout chow....my cats go crazy for it).
Use the frozen food as an occasional treat (I guess you can expand the variety and use frozen bloodworms, frozen krill or maybe even beefheart as well). For very special occasions, give it some live food like chopped earthworms.
ANYTHING, channel cats are the ultimate pig. Try like other have said pellet food both carnivor and shrimp pellets will work. Frozen whole shrimp,fish meat,deffinately not feeders unless they are home grown. Just about any food i can think of will work. Just if you use worms make sure the soil they come from is clean and it would be a good idea to stop feeding him feeders as that is most likely where the disease came from like silirus said. If you decide to use pellets make sure to swithc out the kinds every now and then as well as giving some real food periodicaly like shrimp. Are you planning to get a bigger tank as he grows??? A largemouth bass or some other native species would be cool with him. Well good luck with the disease and all. Hows it going by the way?