How to Tell Male Fighting Fish From Female Fighting Fish

The Siamese fighting fish, also known as the betta, are known for their long fins, colorful bodies and territorial behavior. At first it might be difficult to tell a male and a female apart--but it’s important that you know what you have in your aquarium. Two males placed in the same tank are likely to fight and even kill each other. Becoming familiar with a betta’s physical characteristics will help you determine males from females.

Things You'll Need

  • Bright light
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Instructions

    • 1

      Examine the fins. Males have long, flowing fins while the females do not. A male’s fins can be in different shapes, including a paddle shape or a delta shape.

    • 2

      Compare the sizes. Male bettas are longer than females. Males are typically 3 to 4 inches long. Female bettas are around 1 1/2 inches long.

    • 3

      Examine the bettas for an egg sac. The cone-shaped egg sac is in a female’s stomach area that points toward the rear of the fish. You can see the cone by lighting the fish from behind, allowing you to see “through” the fish. Another way to see this is to look at the shape of the fish from the top. A male’s stomach will come to a sharp end, and a female&'s will be more teardrop-shaped.