I do not think mixing clowns is a good idea, but like jake said you might be able to if they go in at the same time and if the tank is large enough. Clowns will get along good with lots of different fish, firefish, dartfish, tangs, ect., they are a good comunity fish, well most clowns are. Some can be territorial such as the tamato clown is aggressive, but the false percula, true percula, maroon clown are passive fish. Most clowns will get along with their tank mates.