I have three comets that I got at approximately the same time. The only difference between the three of them (now that they are no longer fry) is that one of their tail fins is larger and more spread out than the other two fish. Is this a way to tell what sex the fish are? If they are male and female, how old would they be before they may breed? I understand that they may eat their young - but I was curious to know if it is a possibility that they may reproduce.

http://www.kokosgoldfish.com/breeding.html