How long would you let 2 tangs fight for?

[asylumdown]

I wouldn't let it go on more than a day or two, personally. Seeing that kind of aggression stresses me out. Your Achilles has claimed the tank, you may be out of luck ever adding another tang to the mix. Personally Id take one happy Achilles over 2 or three tangs that spend most of the day trying to kill each other.