j.w - I feed mine exactly the same thing... Wardley's in the Summer, and the Tetra Spring mix in the Fall/Spring. They seem to like it, but of course if I can reduce the waste, that'd be great. I picked up a 20oz bag of this Pond Care brand from PetCo for $15... pretty expensive, but I didn't see any corn listed (and it looks like it has a lot of great stuff in it). I'm going to mix that with the Wardley's. If nothing else, the fish should enjoy the variety.
I do feed mine every day, but now that the plants are growing in and there's a lot for the fish to nibble on, I limit the amount of food they get.