I have an albino channel cat right now, he'll eat everything but absolutely loves sinking shrimp pellets. Now he'll eat feeders as well, anything about the size of a danio at 5 inches, if you can find feeders that small it's not a bad idea to go that way. They'll pretty much eat anything. They almost never come out during the day though. Just a head's up on the rate of growth, I bought mine last June and he was around one inch long, he now is around 7 inches long. They eat like crazy and grow like weeds. If he's already 5 inches long he may last about 4 months in a 55 before he's waay too big for that tank.
Pray for New Orleans and all those affected by Hurricane Katrina