Seriously, we need more info. The more info you provide, the more accurate the responses. Pics would also help. Which Coppens pellet are you using? Have you tried raw shrimp, chopped squid, chopped clams, raw fish fillets, chopped beef heart, earthworms, crayfish, spirulina, etc.? Is the aquarium a new set up or an established aquarium? What is the temp? Are there hiding places for the catfish? Is it being bullied by tankmates? If it's a sucker cat, is there driftwood in the tank? Without more info, the best that can be offered is:
... which of course does not include knowing the name of your fish because it goes without saying. If you don't know the name, please, start an ID thread.