i had a 3 in my 75 gallon a male red spotted and a gold female and male turqoise, all got along but there was some chasing and lip locking occasionaly. id go with a pair and some dithers
I'd say a pair is about as good as it gets. More as juvies untill a pair forms then just the pair and dithers. Sevs (depending on species and variety) can get pretty big. Going with more than a pair long term can be dicey.