Having worked many years in the LFS biz I can tell you the reason that several pygmy angels get along one tank is because 1) usually the fish aren't in there long enough to acclimate and feel comfortable enough to start defending their territory 2) often the tank is small and the crowding makes it difficult for one angel to feel dominant enough to be mean or claim any territory 3) what you don't see is that even given the other reasons eventually one of the angels will start beating the crap out of the other ones and will have to be moved. Usually. That's usually the case for most territorial fish, if you pack enough of them in a small enough space it will prevent aggression issues, at least for awhile. You can try to keep two angels in a 120, and it might work, and it might not, as you've already experienced. You will always hear someone talk about how they did it and now the angels get along fine, but you will often (probably more often) hear that they fought like crazy and one of them eventually died because you couldn't catch it and it got beat to death. Its a little bit of luck of the draw really, along with factors like how often you feed (satiated fish are less likely to fight), how many hiding spaces there are in your rockwork, and what kind of angels you use (in my experience Coral Beauties tend to be less aggressive than either of the Flamebacks, but fish sometimes have a mind of their own and don't always conform to our stereotypes). Hope that helps.
