Temperment varies from fish to fish. My two greenies are like night and day. I have one in a CA tank. I would say his aggression level is about that of a texas cichlid. My larger one in a native tank has the aggression level of a Rd somtimes. They are aggressive to their own kind so I would try to upgrade the tank soon. I had to seperate mine because the larger one would not even let the small one eat. Growth depends on water quality and food (but they do grow quickly). They should max out around 8".