All ... and I mean ALL larger adult catfish are predators. Smaller cats will scavenge more than chase, but the larger they are, the more likely they'll go after something alive. Bug Blues, Flathead and Channels are almost exclusively live prey eaters, although once a scavenger, always a scavenger.
The reason I say this is for the target catfish, the prey has to mimic the food base. Not as precisely as trout flies, but here's an example.
Flatheads, like bass, are structure oriented. Their main prey are sunfish swimming in the same area and the Flathead is an ambush feeder. They lie in wait, using that huge mouth to suck in bream that get a little too close. You want to catch a Flathead, tie a bluegill pattern with an EXCELLENT weed guard so you can pull it through the heaviest cover. You've got to drop this fly right into the Flathead's range of "inhalation", so you can't go too deep into the cover. Hang on, because you could hook a good size large mouth or a 40 pound Flathead.
Blue catfish are like the Great Whites of the fresh water world. I wish they'd eat skiers, but they aren't THAT much like Great Whites. They do, however, cruise the open water, and they'll take any fish that looks wounded or unaware. They are chasers, they will run down a struggling bait fish or bream or bass or anything else they think will fit into their mouth. The mouth is somewhat smaller than a Flathead's, and they don't rely on ambush. They will put on a burst of speed to close the distance and get within inches to inhale the food. Strikes from Blues are generally vicious.
Most other cats will take minnows and other normal small food chain items when they get middle age, settling into ambush and scavenging in adult stages. Any injured bait fish or bottom dwelling species patterns will catch catfish if you put it close enough.