I keep 2 yellow tangs, a naso, and blue hippo in the same 125 gallon tank. I also had a gold-rim but he got ich and died. I added them all on the same day. They never fought other than the initial squabble over the best hang outs.
Generalizations about tangs:
1 Adding them at the same times helps with agression.
2 Mix tangs with different body shapes for best success, i.e: yellow, naso and powder blue, not yellow, purple, and scopas. There is less friction from different shaped tangs. Different genus's are less likely to fight too.
3 Add the most agressive tangs last. I believe clowns and sohals are the most agressive; powder blue, achilles, powder brown (and others from this genus) are next; then yellow, purple, and scopas are next, and nasos and hippos seem to be the least territorial.
Note: every tang is as unique as every person, while these observations are generally true, there are always individuals who didn't read my post and therefore, don't conform.
Mike
I live in my own little world. But it's OK, they know me here.