Clowns as a group are very fascinating fish. The maroon clown is a bigger species than the false perc, and slightly more aggressive towards other clowns, but usually is very peaceful towards other non-clown fish in the community tank.
They are amazing as a group, because they actually can change sex through their lifetime (actually, a few marine groups do this--see the diadem anthias page). They start out as males when young. If bought as a pair, the more dominant of the two will change physically into a female, and they may become a mated pair for life. The less dominant one remains a male, which is usually considerably smaller, but usually more brightly colored. If kept alone, the lone clown will become female on his own.
I bought a 60gal tank that came with a pair of these clowns, and they were beauties. Especially the female, who was a sea monster... she was about 6" long, I think. The little male (he is the one shown above) was so cute, he constantly followed at her heels. It was very cute how she picked the better nestling spot, in this case, a large sebae anemone, and the little male got the "next best thing", a smaller piece of ricordia, like the loveseat next to the couch. Very sadly, the big girl didn't make it for long after the move, I guess she was just too traumatized by all the change. She developed a bacterial infection and died despite my efforts to save her in the hospital tank. It broke my heart :-(. I have since wanted to avoid matching the little clown with another, because I am unsure if it is now male or has already turned into a female, since he is the dominant clown in the tank now.
Besides, the reef tank is almost overstocked anyway, so I don't want to push it with anything else.
But i did want to mention one issue. Beginners often try and buy an anemone to match their clown, having heard of the famous symbiosis that can exist between the two. However, please read the profile I have on my sebae anemone first before you buy one. Anemones are difficult animals to keep, and require higher lighting than many corals (special reef lighting only), and are very picky about water conditions.
Without these things met, anemones tend to shrink and die gradually, which is very sad for an organism that has no lifespan at all in the wild (they do not age and could in theory live for centuries under the right conditions). Also, clowns do not need to have an anemone to stay happy and healthy. They can live inside all sorts of things, including coral mushrooms and other corals that are easier to keep, or they are fine with nothing at all.