Catfish by my guess will not eat 2" mudminnows until the cats are about 8" to 9" long. 1" mudminnows maybe when cats are 4" to 6" long. Feed the small catfish fish sinking fish pellets from the pet store. If you can keep the ich off them, they will grow fairly fast. If growth stops or slows water quality is the cause.

I doubt the catfish will eat tomatoes or lettuce if other things are available such as worms, raw fish pieces, cooked or raw chicken or beef. Vegies will not supply adequate nutrition and protein. Remove uneaten food daily.

Instead of catfish consider raising bullheads. Yellow bullheads are a great aquarium fish. They will also be fairly predatory and a little more omnivorous. They will get big, require lower water quality, and will adapt to aquarium life better than catfish.

aka Pond Doctor & Dr. Perca Read Pond Boss Magazine -
America's Journal of Pond Management