I have a Red Devil in a 120gal. tank. He is one bad son of a gun!!!!!! I do love him alot, they are fun to watch because they rearange the tank how they want it, so he's always busy. But, he chases everyone around,(Convicts and my Dempsey,) luckily they are fast enough to get away, or they would be toast!!!!!! I tried to put my Green Terror in with him...... NOT a good idea, needless to say my GT is in a 65gal with only one other little Sunburst (I think) chiclid.
But, if you're gonna get one, like everyone else said, plan on having a big tank, and not too many fish can go in with him when he gets mature, other then that, they are very interesting fish, I just love mine.....
Good luck on whatever you decide.
Jeanna