hey azin...its all depends on the fish i have a laperdei, senegalus and ornate with my rays and the only thing was right when i introduced my first motoro the ornate bit its disk once or twice but has left it alone since
i have a 6"(or around) ornate in with my 4"-5" rectics and havent seen any aggression at all but i also introduced them in the same day so its not like one was in the tank then the other i added both at the same time well hope this helps