I add them slowly. Cos all 1 time high chance of getting ich.
unless u already have copper in your tank then can add many in a time. But slowly acclimatise to get the new angels to the copper in yr tank.
If they fight, Ill take the agressive one out and throw in my sump tank. Then add it back after 1 day. keke. problem solved. for me at least.
I've 10 Angels in my 4 ft tank. Thinking of 2 more than will stop already.
Do what my shifu VTec did for adding of new angels and you should not go wrong.