I don't believe in powerheads for discus. these fish do not like current. I run an ehiem 2178 and a rena xp3. I have spray bars on each side for surface aggitation. I want the waste to settle on the sand. it's easier to vacuum. any area that the powerhead pushes water will probably not be used by discus. it's hard to say how much to feed. besides my 8 discus, I also have 4 festivums and 25 lemon tetras that also need to be fed. my discus eat the bloodworms, brine shrimp, and fd blackworm pretty fast, but flake and granules they let it sit on the bottom, then blow on it to eat. it may take an hour for them to eat all the flake. if you have any food left after an hour then your probably using too much.