The males will reach up to 10", the females up to 6". They should be an a 55 gallon tank minimum for a pair. These fish can be kept with an exceptional amount of non-cichlids including surprisingly small shoaling fish - they completely ignore non-conspecifics. They accept most foods - flakes, pellets, bloodworms, brine shrimp, etc. I've also found they are always nibbling on the zucchini I use for the Royal pleco.
I keep mine in a 75 gallon, I find the depth makes a nice difference. They shouldn't be kept with too many other types of cichlids because of their docile nature - geophagus will work, and severums. Of course, I wouldn't force a pair into a tank with other cichlid as cichlids naturally hate each other and i'm not into gladiator tanks.