I understand that that oddball said that discus have to be alone or in groups of five, but ,and I dont know if I understand what he said properly, but do you mean that you can only have discus in tank, wheather it be 1 or 5 fish. but if you are saying it is ok to put other fish in the tank ,just keep the discus by its-self or in groups five ,well I dont have a problem with that.