Sex Guppy Fry: How To Tell The Difference For Male & Female

It’s best to wait at least 4 weeks to correctly determine the sex of guppy fry. During weeks 1 and 2, female and male guppies look exactly alike. However, once the gonopodium (anal fin) develops, you can easily tell the difference between the male and female guppy fry.

Adult Male Guppy - Parts
Adult Male Guppy
Adult Female Guppy - Parts
Adult Female Guppy

1. Examining the Guppy’s Body Shape and Coloring

Male and female guppies have distinctive body shapes and colors. Guppies that are very slender and have long bodies are usually males. On the other hand, female guppies tend to have a rounder shape and bigger bodies compared to males.

2. Note the size of the guppy

Male guppies are usually smaller than female guppies. Females grow up to 2 ⅛ inches while males grow up to 1-⅛ inches.

3. Look for bright coloring and patterns on the guppy’s body

The more colorful guppies are more than likely males. Male guppies are covered in bright colored patterns and their tails are usually brightly colored as well.

4. Check for the gravid spot on the underside of the guppy’s tail

Female guppies have what is called a gravid spot. The gravid spot is a dark area located on the underside of a female guppy’s body usually near the anal fin and tail. The gravid spot gets darker as the female gets closer to delivering her young.

5. Examine the length and shape of the guppy’s anal fin

The anal fin is the smaller fin right before the tail fin found under the guppy fish. Male guppies have long and narrow anal fins that are slightly pointed (gonopodium). The female guppy has a triangular anal fin. The gravid spot is right above the anal fin.

6. Look at the shape of the guppy’s dorsal fin

The dorsal fin is the fin that is on the top part of the fish’s body near the head. Male guppies tend to have longer dorsal fins while female guppies have shorter dorsal fins.

Guppy Fry Female To Male Ratio

Once you can determine the gender of your guppy fry you can then separate them to prevent overpopulation. A good ratio is 1 male to 3 females. To prevent breeding, try to separate the males from the females as soon as possible.

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