How can you tell what gender your fish is?

guppies-you must wait until they are at least 1 1/2 months old and the males will be more colorful and possibly a little smaller females will have a bigger gut

AnswerYou can tell very early, the females will have a dark triangular area on their belly close to the anal fin. As they age the male's anal fin will transform into a gonopodium. This is their sexual organ. It just looks like a pointy anal fin. The females anal fin stays the same and is normal looking. It is very easy to distinguish if you have different sexes side by side that you can compare. The males of most livebearers can be identified this way. Including guppies, mollies, sWordtails, and platys.