Hi there... With discus, ime, they are happiest when there are at least 6 of them.. You could easily have 6-8 along with a large school of rummys or cards with a bn for algae etc. With your other fish just remember the best temps for discus are 82-84 so the other fish will have to be comfortable at those temps as well. Good luck with your tank and lets see pics please.. HTH Sue