My Pinima runs the tank basically, he will go around and ocasionally nudge the others, basically asserting his dominance. The 6 temensis I have in there don't really bother eachother and the Azuls tend to leave eacother alone too. So the only aggression problems I have is the Pinima. I haven't added dithers or anything as there really isn't a problem IMO.
But sorry about my rambling, aggression amongst bass would be considered fairly normal IMO.