How big is the yellow tang and how long has it been in the tank? I would catch the yellow tang once the pbt is ready to go in the tank, rearrange the rockwork, and then introduce both at the same time. It may help if the pbt is the smaller of the two fish. IMO, depending on the size and particular individuals, the pbt is likely to be the stronger and more aggressive fish. If introduced properly and depending on the individual fish, the two fish should be able to coexist in the same tank.