It may be peaceful, whether it would be that way in your tank is another story, much depends on the size and dynamic of your tank.
That said, normal JDs are one of my favorite Central (North)American cichlids, I have snorkeled with them in the Yucatan, and seeing them in nature has given me deep respect. They are usually found with large shoals of live bearers, they watch to gauge the threat of danger, and seldom stray from heir hide outs, though their spawning territories can be 4ft X 4ft X 4 ft.
They do very well with no other aggressive cichlids present, but often suffer a bit when with other robust cichlids around.