Angels can really be bastards and some territorial fighting and nipping is to be expected when there is more than 1 in the tank. I would say no more than 2 can go in that tank. It would help if you bought two out of the same tank and added them together but it's not necessary.
Or if you were hoping for them to breed you could get 4 small ones of the same type and stick them in the tank and then rehome 2 of them once they pair off. Breeding however can cause more aggression in the tank.