A variety of foods is best. Live, flakes, pellets (make sure to presoak them before feeding, so they don't swell up inside the discus' stomach and cause a blockage), and frozen foods . If fish seem to become dependent on only one type of food, do not feed them for a day or so. They will become very hungry and are more likely to eat other foods again. I am still in the research phase of discus as we speak. I will be ready in a couple years. I buy fish to breed them, and do what I can to keep the hobby alive.......