Sorry to hear about the clown tang. But I tried something with my tank that worked great.
I have a Chevron tang, purple tang, Red Sea Sailfin tang, and yellow tang all in a 150 gallon tank for at least 6 months now. I saw a tomini tang that i just had to have; so i bought him. Before adding him to the tank since i new WW3 would likely ensue i place 3 small mirrors around the outside of the tank and the tangs in my tank went after their own reflections allowing me to put the tomini tang without much stress or aggressiveness from the other fish in the tank.
He is now swimming around like if he has always been there.