I think it will be ok if you grow them up together. My synspilum was beating on my O and I had to move the O. The syn pretty much rules the tank (220) even over the jag that is nearly the same size (in lenght, the jag winds in thickness but the syn in height). But my case is a good one for individual personalities, my jag is a wuss for the most part (doesn't seem to like other parachromis though)
