I have mbunas, and it's been my understanding you should overstock them becasue of aggression and then overfilter becasue of the stocking. I haven't really had any aggression issues (at least since my red zebra died) and my Kenyis are breeding like crazy. I've got 5 Kenyis and some other cichlid (wal-mart "assorted Cichlid;" he's orange) with a huge (6+ inches) syno catfish and rhino pleco in a 55. I have three other babies in another tank and I'm moving them all to a 75g soon. they seem to be doing great.