I have 3 in my 135g, started out with 6. In my case there was a mated pair already in the tank so maybe with yours being a single clown it might go smoother. In my case, two ended up jumping, I believe due to agression, one I removed and the last somehow made it and is now accepted among the pre-existing mated pair. It tooks months for this to happen. I would suggest that it can be done, though, it is an obvious risk, as demonstrated, nature *will* take it's course regardless of our plans.