i think this can be done with a huge tank, however with the average size tank the dominant clowns will often pick on the smaller clowns. you can keep several immature clowns together without problems however when they get larger, they can kill eachother. if you go to a store like petco, notice the tanks with 10+ clowns and figure out which one is the boss. then figure out which one is on the bottom of the pecking order.