How to Tell the Differences Between Male & Female Fish

One of the most common inquiries fish owners have is how to determine the sex of their fish. Knowing the gender of a fish aids in breeding and naming the pet. Fortunately, the sex of species in which males and females look similar can be deduced through an examination called venting.

Things You'll Need

  • Light source
  • Four buckets
  • Room temperature water
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Instructions

    • 1

      Fill all four buckets with room temperature water. Place all the fish to be examined in the first bucket.

    • 2

      Pick up a fish with wet hands. Look for slightly different body shapes in the same species of fish. Look for uneven, round shapes, which are characteristic of female fish. Look for thin, long body shapes amongst male fish.

    • 3

      Rub the first pectoral fin and determine if it is thick and stiff. Check for sharp, pointy edges, which is common in male fish.

    • 4

      Feel the fish's head for tubercles, or small white spots or bumps that develop on mature male fish. Touch the gill covers and pectoral fins, as well.

    • 5

      Turn the fish on its back and examine the anal opening, or vent. Notice how a female's vent appears larger and round, whereas a male fish's vent is thinner and indented.

    • 6

      Place the male fish in the second bucket, the female fish in the third bucket, and the undetermined fish in the fourth bucket. Repeat the process until you have determined the sex of each fish.