The yellow tang was the first in the tank about 10 years ago (maybe 1.5 inches then). About 9 years ago the blue tang was introduced (less than an inch). A few years ago the sailfin went in (maybe 3.5 inches). The yellow and blue were approximately somewhere between 4 and 5 inches by the time the sailfin was introduced so all fairly similarly sized.
A couple years ago I added a small naso tang and kole tang (maybe 3 inches each) as a temporary hold for someone else. The fish all got along well. I have never witnessed any prolonged aggression between tangs other than the initial feeling out period for a day or two.
Unfortunately there was a major shortage of available food and a slight algae bloom when I tried to add enough to keep everyone fat and happy. Within a couple months I could visibly see all tangs excpet the yellow and the kole were getting skinnier. Tried to remove the Kole and naso but could only catch the sailfin and naso. For the last couple years I have had the yellow, blue and kole with no issue.
A few months ago the kole started taking bites out of a leptastrea and my prized birthday cake favia so he will be on his way out as soon as I can catch him. The blue tang has recently developed a taste for nipping at my favorite zoas so he will be on the outs soon as well. Sadly I will be down to only one tang. On the bright side I get to hunt for two more tangs to toss in the tank