If it were me, I would just get different tangs anyway.
Unless its a huge tank (1000g+) or they have a reason to school (threat), tangs usually do not school in our tanks like they do in the wild. They will likely school for the first couple weeks, but once they realize there is nothing to fear, they will start doing their own thing and may even get territorial with each other.
Obviously, there are always exceptions.
Anything CAN be done. The question you should ask is: SHOULD it be done?
When it comes to the amount of tangs in a tank, there is the right thing to do, and what you can get away with. Tangs have and can live long lives in nano-cubes. That does not make it right. Do not do the wrong thing until a living animal dies to decide: oops I guess that was too many.