Are there any other fish in the tank? A bullhead catfish would eat anything it could fit in its mouth....not to mention it will outgrow a 50g tank.
Could you list your stocking (or future stocking plans) for the tank?
Bushy/Bristlenose plecos are good catfish to have. They will eat algae and prefer to have driftwood in the tank. Most will hide, so you won't see them much.
There are alot of catfish that are nocturnal, so you won't see them much. Raphael catfish, Pictus catfish, and other plecos under about 6 inches would be good, but you won't see them too often.
Anything in particular you like?