I have added a new clown in the past, but it was the same kind of clown, One died and I wanted a pair so I got another but it was MUCH SMALLER than the existing one. I've done this twice with no problems at all. I did a longggg time ago have 2 pair of the same breed and that didn't work out so well. I ended up removing two of them. I've never mixed breeds which is what I would like to do. In my 125 I have false percs with an anemone. In my 150 I have tomato clowns with an anemone. I do have another anemone in my spair tank that I could add to either tank and would like to get a pair of black perc clowns. My preference would be to add them to the 125 which houses the false percs.