Mine are still relatively young (~5 months) and small (2" long, 3.5-4" tall), and I've had them since they were barely bigger than fry, and I'm down to just one pair in my 55g.. they were chasing the others and not letting them eat (but are leaving all the other smaller fish alone) so I had to pull out the ones being picked on. I'm not even convinced the two remaining ones in my 55g are a "pair" exactly, but they never leave each other's side.
The two that I removed are temporarily in my 20H and they seem to stay as far away from each other as possible. It took them several days to start eating again.. they still hide a lot. I am not sure how long it will take them to get over being terrorized, but once I am certain they are doing fine I am going to take them to my LFS.. I don't really have the space to keep them separately, the 20 is supposed to be my quarantine tank.