Well the great thing about these fish is that they eat absolutely anything.
(also annoying when it comes to finding suitable tankmates)
Some times I have the ambition to go out hunting for crawdads, most of the time not so much.
They are only a buck at my pet store I go to. Um, out of season, some times Ill feed him frogs that you can catch anywhere around here. Or just misc. fish.
When tadpole time comes around (which is right now) You can get them by the thousands with just a small goldfish net and a little time down at any retention pond.
Switch things up on occasion and give him sinking algae wafer food, and shrimp pellet food for bottom feeders. I figure it probably has some vital nutrients that he is not getting from most of the things I feed him.
Just play around with it, see what they like and what they dislike.
I do have the feeling that, having raised mine on mostly live foods is why he is so violent towards others. So, if that is true then beware of that. (this is my first big cat, so I don't know how he would react to others had I raised him on frozen food and or pellets)
He is quite comfortable with my arm in the tank though, which is nice. He doesn't mind being pet, or hand fed.