Hard to say.
My big angel killed off his first tank mate (was my fault...had em both in a 10g).
I've since moved him to a 25 and over time added 3 juvies. He likes to flash em, but they only get on his nerves when they're in "his" spot. Otherwise he could care less.
I'd imagine, with a well designed 120g, you shouldnt have a prob with 6 angels. Specially if you take the route jasonit suggests. Just be warned if someone decides its breeding time, all the space in the world may not make a diff LOL
aka Cycling Guru and the Ich Slayer
*glares at Terry and QTOFFER*
Card carrying member of FTAS & GCAS.