Oooo maybe no on the purple then OP, that six foot mark is usually a minimum distance when it comes to tangs. Yellow would probably be better temper-wise and space since they are smaller than purples. You might be able to do the purple if you rehome the orange shoulder just cause those get massive as well (seen many at the 12 inch mark and above). If a purple feels cramped it will be a terror. They also dont like other tangs and new tangs that they think challenge their rank so to speak. My rank in my tank right now is my sohal as tank boss, my sailfin looks to be coming in second instead of the purple which he is NOT happy about, and then my white tail. She does her own thing, only gets mean when they swim in her caves she frequents. Its all about territory, rock work, food and space with tangs