I know that many people say that balloon mollies are just like every other livebearer, but to me it seems that their anal fins are shaped a bit differently (which leads to discrepency when trying to sex them). Both the female and male anal fins tend to look somewhat rod-like, but the female's fins seem to spread out slightly more than the male's (this is what i've gathered from my two). The male's anal fin is obviously more cylinder-like. You have to look closely to tell the difference.