Not an optimal thing to do, but if you are gonna do it, those are the clowns to do it with. I strongly recommend though, that you catch the existing pair out, move a few rocks around, and drip them in the same bucket and add them together. This will increase the chances of harmony....but it is not a guarantee. I had two breeding pairs of ocellaris clowns in a 75 gallon...it was only planned as a temp measure to begin with....and in the 3 weeks they were together, no fins ever got nipped or damage done, but those cats were always in each others grill as long as the lights were on. But, like I said, it was only temporary and they may have learned to get along if I had left them. Funny thing is, the troublemakers were the new pair that got added. And, no one got hurt or damaged, but they twirked and danced with each other all day lon.