Dude, I have a 60g with a pair of 4-5'' festae, a 3'' con, a pair of gold saums at 3'', a 5'' distochodus, and 3 vieja synspilum at 4-6'', and I have minimal problems with aggression. Oh yeah, I also have a 6'' crenicichla sveni (cause all tanks need at least 1 pike..). Granted with all of this overcrouding, I have 15X an hr filtration and I do daily 15% waterchanges. The only casualty has been a 3'' caquetia myersi I added last week. I think that it was killed by my female festae.