Tangs
I have a purple tang(red sea) myself that "rules" my tank as well. In order for me to get any other type of fish for my tank, it will have to go. I want a sohal tang as well. I would like to keep both and probably could with a rearranging of the rockwork, but that is truly a pain.
You can get other tangs that do not look like the same shape. If you do want to add another, it would be best to reaarange the rocks or turn the lights off for several days and cover the sides of your tank and you may be successful with that. Then when you turn everything back on, it should be OK. This is a trick I have heard that should work. Of course if your tank is big enough, then it may not be a problem.
Maybe others can give better advice. Thanks, Steve