Originally Posted by Fishlover1601
How do I tell when I am at the store if they are male or female?
#1- Ask the sales clerk. If they don't know how to sex them, I'd seriously consider not shopping there as they probably also don't know the proper way to maintain fish either. (Sexing livebearers is about the easiest thing a salesperson should know.)
#2- Females have a somewhat triangular anal fin while a males' anal fin rolls up to become the gonipodium for transmission of his sperm.
(If you are still unsure what to look for, look at a pair of swordtails. Male swordtail have both a sword and gonipodium. Females will not have a sword so it will be easy to compare fins. The same comparison applies to all livebearer's anal fins, swordtails have the extra piece (the sword) which just adds to the help.