How to Know If Your Fish Is a Girl

Unregulated breeding can quickly overwhelm an aquarium's capacity and kill your fish. To prevent overpopulation, you must be able to identify the sex of your fish so you can make sure that the males and females are separated and can breed only in a controlled environment. It is difficult, but not impossible to identify a female fish based upon her unique physical characteristics.

Things You'll Need

  • Magnifying lens, head mounted
  • 2 plastic tubs
  • 1 small bucket
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Instructions

    • 1

      Put on a head-mounted magnifying lens, which you can purchase from a jewelry supply shop.

    • 2

      Fill two tubs of different colors with water and place them side by side. Fill the small bucket with water from the aquarium. If only fresh water is available, treat it as you would the water in your tank by removing the chlorine and chloramine with a water conditioner.

    • 3

      Wet your hands by dipping them into the bucket of water, then remove a fish from the aquarium with wet hands and turn it upside down with the head facing away from you. Examine the vent between the anus and the anal fin quickly. Female fish have a larger vent to lay eggs.

    • 4

      Examine the mouth of the fish quickly. Female fish will have a smaller and thinner mouth than the males.

    • 5

      Examine the dorsal fin quickly. The female fish's fin has a rounded shape, unlike the pointed dorsal fin of the male.

    • 6

      Place female fish in the first tub after the examination, and place male fish in the second tub. Do not keep the fish out of water for longer than 30 seconds at most.