Although generally the rule is to only house one pair of clowns per aquarium, it is largely dependent on the size of the aquarium and the number of host anemones available. Obviously certain species of Clown fish are more aggressive then others causing incompatibility.
We have a customer currently keeping
A.chrysopterus, A.melanopus and
A.perideraion in the same aquarium. This is largely successful because the aquarium measures 12' x 4' in footprint. There are many anemones present and all the clown fish have been together for 2 years. The chrysopterus and melanopus are in pairs and the perideraion are in a group. Interestingly, the melanopus and perideraion alternate between anemones day versus night.
Hopefully this is helpful.
Big Al's BC