Here's the only rule I ever heard about the amount of food to feed...bear in mind I don't use this, I just feed what I "think" is enough...but...
A breeder of oscars told me he feeds the fish an amount of food equal to the size of the fishes' eyes to its mouth. Got it?
Im feeding Angel Formula, Formula one, nori sheets, spirulina flakes...sometimes drop in a couple of pellets of Nutra Max.
I have a Juv. Harlequin Tusk, Maroon GS Clown, and a 6-line wrasse in with him.
Thank you