I have have two Percula clowns for about 6 months and just added a small Clarks clown. The female Percula and the Clarks don't get along real well but they both stay in their own little areas. They occasionally square off against each other but they never bite or nip at one another. I don't know what will happen when the Clarks gets twice the size of the Perculas. I only have a 55 gal so I would think that there would be plenty of room in a 135 for them to stay apart if they don't like each other. Do you have "Clownfishes" by Joyce Wilkerson. I think it goes into a little on species compatability but I am not sure. It's a great book anyway.