Sexing fish

For obvious reasons it is important to know how to tell the sexes apart when attempting to breed any fish. Sometimes it is a simple task while other times it is quite difficult or impossible. Here is a quick general  guide on some common aquarium fish.

Livebearers. These are almost impossible to mistake. The males have a modified anal fin to allow them to copulate,

Photo By: Kylie Hogbin

Photo By: Mikael Gullberg

With the Guppies pictured above it would be almost impossible to make a mistake. Even when the sexes are quite similar as in Platties the anal fin is a 100% sure way of telling male and female Livebearers apart. The females anal fin is just like the anal fin of every other fish. The males is modified into a hollow tube and is unmistakable.

Barbs. Usually male Barbs are more slender, more colourful, and slightly smaller than the females all of these differences are more easily noticed when the fish are in breeding condition.

Pair of Bluelined Barbs
photo by Andy

Then the two sexes are seen side by side it is relatively simple to see the differences in most Barbs.

Cichlids, In general another easy group to sex. In some cases so big is the difference that the two sexes look like different species.

Male Ram, photo by Andy

Female Ram, photo by Andy

It is the male Cichlid that tends to be the larger of the sexes, and usually the more colourful. Another good point to look for is the fins, the dorsal and anal fins inparticular, these tend to be longer and more pointed in the male.

Blue male, Yellow female.
photo by Andy

This is not a tank bred trait, these fish are like this in the wild.

Rasboras, The female is usually the larger of the two, the males tend to be more brightly coloured and slimmer.

Female above male below.
photo by Andy.