I tried this not too long ago with my established pair of true percula clowns that wouldn't host the RBTA and I added a pair of Clarkii clowns. They got along for a little while and then when the clarkii decided to host the anemone (the 3rd day in the tank), the percs decided they wanted it as well. Both pairs began tugging on the anemone and actually ripped a few tentacles off it! Needless to say, I separated it, but the damage was already done and the anemone died that night. From that point on the Clarkii got no rest, and died a few days later from the damage the percs inflicted on them within 1 nights time. Maroon clowns are less aggressive as juveniles, but even still I would say the only clowns I recommend mixing are the ocellaris variations. I've had good luck previously with groups of 6 or more in the tank (added at the same time and as juveniles). As adults, Maroon Clowns are true terrors. My LFS had to take 1 out of their 1,000 gallon reef display because it was going after everything that came near its anemone. Even tangs over a foot long! They replaced it with 6 ocellaris (a pair of mis-bar, a pair of black and white, and a pair of regular color). Now the massive reef tank is peaceful again.
