Going more than two runs the risk of one getting beaten up. That's by the book. I've heard of people putting three together and they got along. Seems more like luck to me in smaller tanks. To go two pairs. I would say 120+ so that there is plenty of space for each pair to claim their area.
In your LFS
, they get away with multiples of many types of fish in smaller tanks due to the fish not being around long enough to get a territory established. I think part of it is the way the tank is set up. One of my LFS
has a big corner tank (probably 250g or so, maybe more) with tons of fish. Multiple Tangs, Angels, rabbitfish, etc. Almost no live rock. You'd think there would be constant aggression, but they all seem to get along. All are healthy and he says some have been in there for years.