Males usually top off about 10" give or take, females slightly smaller.
Here in Panama they I've in loose shoals of about 6 to 10 individuals in pristine, large bodies of water, but pair off to separate 4 by 4 ft territories during he spawning season.
I kept them a while, find they are usually aggressive with each other in smaller groups and in small tanks, (tanks under 6 ft in length), and usually end up as one alpha individual, or if you are lucky, a compatible pair. But you've noticed that already in the previous owners tank.
In my 130 to 150 gallon tanks they were usually fairly mild mannered until they mature, but then, in that size tank I usually ended up with a pair after the male took every other cichlid out almost over night.
![20150310_180031[1].jpg](https://www.monsterfishkeepers.com/forums/data/attachments/1037/1037128-eb360cb38f948fcbc558cab638115385.jpg?hash=6zYMs4-Uj8 "20150310_180031[1].jpg")
