any tang from the zebrosema family will most likely fight till one dies..if you have enough LR and a large tank 3 yellow tangs can be done if introduced at the same time and monitored...i do not recommend imho that this be done with a tank at least 180 g
if you want the purple tang which is a beautiful fish try trading the yellow tang to you lfs or give it to a friend then get the purple tang that is what i did originaly.