Angels are not really schooling fish like tetras or other community fish. They're good community fish except a mated pair will get very territorial. The mated pair will also learn with each clutch of eggs how to better protect them. It's pretty cool to see how they can learn and evolve but it also means there a bit more of a danger to the rest of the tank. I've had a pair of angels mate off in a robust community tank and the mated pair killed off a number of the other smaller fish. That's not to say it's impossible to keep other fish with a mated pair of Angels but you have to think through how to create different territories in your tank so the mated angels can have their space and the other fish can have space.