How Do You Know If It Is a Male or Female Betta Fish?

Betta fish, known scientifically as Betta splendens, are also known as Siamese fighting fish. They are known for their wide array of colors, including red, blue, green, black and white, and their aggressive and sometimes deadly territorial behavior. Correct betta sexing helps an owner know which fish to breed and which fish to keep apart. Sex bettas when they are around 11 weeks old, which is when they have their adult shape.

Things You'll Need

  • Flashlight
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Instructions

    • 1

      Examine the fins. The fins on a male betta are between twice and four times as long as the fins on a female betta. Males use these brightly colored fins in their dominance displays.

    • 2

      Look at the betta's body. The male betta has a slender, long body. The female has a round, compact body.

    • 3

      Look closely at the betta's gills. Bettas have a membrane under their gills, which is called a beard. The beards are more pronounced in males.

    • 4

      Check the betta's body for breeding stripes. These dark stripes appear along a female bettas body when she is in the presence of a flaring male. This is typically only detectable in females with darker bodies.

    • 5

      Shine a bright light from one side of the betta's tank and look at the fish from the other side. If the betta is pale, look for the presence of ovaries. The ovaries are a roughly triangular mass behind the dark mass of the intestines. It will only show up inside female bettas.