Clowns are all born male......the dominant in a group, even a pair, will become the female, and the next dominant will become the breeding male. If the female dies, the breeding male will step up, and turn into the female, and the next in line male will breed. Best bet IMO is to get two very very juvenile clowns so you know both are male, and then hopefully the dominant will turn female without too much fighting....they will fight to secure dominance. You can get a two from seperate tanks, and have a serious mismatch if the smaller less dominat, was the dominant in another tank, and is the female, or you could get two females.........two very small juvis are going to be male. An established pair would be nice too, and save the trouble.