I been told to keep them in either 1 or 3. Sometimes 2 will be too aggressive to each other but If there are 3 they dont get as territorial. But it also depends on the individual fish, as some are more agressive than others. Keeping more than one will of course depend on tank size. How big is yours?
I think the tank you have one in is too small. Angels get very big (my adult is 6" accross and 8" high) and need a higher than average tank to house them - at least 18". Many also say that angels should have 10 gallons each in addition to this.
I'd say you have to get a larger tank or give the one you have away.
