[Haloreef]

Before I add a new tang I make sure the tank is very well fed for a couple of days prior to the new addition. Trying to reduce aggression due to food compitition. I also set a mirror in one corner of the tank. Once my Powder Blue has found his reflection he ignores anything else around him. I then add the new tang (to the other end of the tank). I leave the mirror up for a day and then remove it and sit back and observe the tank. If there is still a problem I repeat the process.
It has worked six times so far.
Just my two cents.