I currently have 4 Blue Greeens in my 6 foot reef. Two were transferred from a 29 gallon 2 years ago. I added three others after introducing the 2 from the 29. Since then, the four that reached the same size have coexisted peacefully. The fifth one (and smallest) was constantly being harrassed and pecked at especially at feeding time. I was able to scoop him out and placed him in my sump until a fellow reefer agreed to take him off my hands after some wounds healed. I think the key to keeping many schooling/shoaling fishes is to feed a lot....something many reefers are unwilling to do. Along with my other fish, including anthias, tangs and an angel, my reef tank is fed a minimum of 5 cubes frozen, a pinch of pellet and half a sheet of Nori per day. Nitrates, phosphates undetectable with vodka dosing and a large ETSS downdraft skimmer. Fat, healthy fish are less prone to fight. I really believe much of it has to do with food rationing. Once a new arrival sees what is being fed daily, they rationalize how hungry they are and fight or flee, with many times the weakest and smallest paying the price. Just my .02