Mixing clowns is hit or miss. I love clowns and have false percs and tomatos living peacefully in my 75 gallon but bought them all at 1 inch size and introduced them at the same time. They pretty much ignore each other. Tomatos can be feisty if you add another clown later. In another tank I keep sebae and skunks, this is a 125 and they also ignore each other, also introduced within a week of each other. Maroons are a different story... they are just plain mean! I never keep them, they even can kill damsels. Again, what works for me may ot for you. Best bet: buy juvenile clowns and put them in at the same time. I have never had problems doing that.
Mike
I live in my own little world. But it's OK, they know me here.