some things to try...... shrimp pellets are a favorite in my tanks, also frozen bloodworms, frozen beefheart.....
unless the fish looks thin it is probably eating, it just might not be doing it while you watch. additionally, most fish can go several days between meals so if it stuffs itself today when you're not looking it might not need or want to eat tomorrow. my raphaels are prime examples of catfish hiders, it is rare that i see them at all much less eating. they are always fat and healthy when i go looking for them tho. this is common behaviour among catfish from what i have seen....
good luck