If you still have measurable ammonia and nitrites in your tank, as you noted in your other post, those fish shouldn't be in there to start with. Measurable ammonia and nitrite levels means your tank isn't done cycling.
I can't speak from experience since I only have one clown, but I believe folks normally pair up clowns of unequal size. The larger of the two will become the female and pretty much boss around the male. Two clowns of the same size though, I believe, will be prone to fight until one gets bigger than the other.