Depends on the size when mine was small chopped mussel maggots worms prawns (loved worms...) like all catfish eats all dead food (sometimes requires training) such as shrimp, crab, crayfish and fish meat. Shovelnose catfish loves living food and it is beneficial to give them live food every now and then however this should never be their main diet.
they do tend to feed a lot more at night the smaller they are a friend of mine has one that is blind and he is out all the time best thing is to drop the feed, (worms are good) down where he is at night time just before bed. When he gets bigger he will eat no problem
I feed earthworms, minnows (frozen, then thawed), FW shrimp. Once he's got some size, I'll add crayfish and other things of that nature to the diet. He's kinda small right now.