If you get them as a pair to start then you are better off. Trying to build a pair later in the game is where the trouble starts. You can slowly get them accustomed to each other, say through separate compartments in a tank, but its not a sure-fire method for pairing. One of them must be smaller than the other. This one will be the male. As deadmeat says they are very aggressive, towards other clowns and even fish who come into their territory. I've seen a big maroon push a goldie that was swimming near its home right into an anemone as food. Scary. But, back to the point, try to get them as a pair to start. That's your best bet.