Cory cats like eating flakes if they fall onto the bottom of the tank. Another thing you might want to try is sinking shrimp pellets. Alot of bottom feeding fish seem to love them.
I would recommed Tetra Tabimin or JBL pellets. They are a good staple diet for corys but make sure you over other foods as well like bloodworm, chopped earthworms and flake.... variety is the spice of life !