It has been interesting watching them so far. There are three that hang around together all the time, and one that kind of sulks in a corner. The large yellow is dominant, and when he sees one of the other ones picking at a rock, he will nudge it over and take the place. The subservient one simply moves over a couple of inches and then they just sit there eating together. It doesn't seem to be a hostile, attacking kind of thing. All the tangs seem to know their place and are comfortable with it (except maybe the sulky one)

The PBT and the yellows completely ignore each other. I think one thing that helps is that the PBT is about the same size as the yellows. I actually ordered small yellows, but these are bigger than I expected.

I'll keep updating the thread as the social dynamics change.