How do you tell a female guppy from mosquito fish?

Guppies (Poecilia reticulata) and mosquito fish (Gambusia affinis) are two common species of fish that can be found in freshwater habitats around the world. While both species are small and have similar body shapes, there are several key differences between them, particularly in terms of their appearance. Here are a few ways to tell a female guppy from a mosquito fish:

Size and Body Shape:

- Guppies: Guppies are typically smaller in size compared to mosquito fish. Adult female guppies usually grow up to 2.5 inches (6 cm) in length, with a slender and rounded body shape.

- Mosquito Fish: Mosquito fish tend to be slightly larger than guppies. Adult female mosquito fish can grow up to 3.5 inches (9 cm) in length and have a more elongated and cylindrical body shape.

Coloration:

- Guppies: Female guppies are known for their vibrant coloration. They often display a wide range of colors, including various shades of red, orange, yellow, blue, and green. These colors can be solid, patterned, or have intricate markings.

- Mosquito Fish: Mosquito fish females are usually less colorful compared to guppies. They typically have a dull olive-green or brownish coloration with a silvery sheen. Their fins may also have some color variations.

Tail Shape:

- Guppies: Guppies have a distinct tail shape, commonly referred to as a "fantail." The tail is fan-shaped and spreads out gracefully, often extending beyond the body.

- Mosquito Fish: Mosquito fish have a different tail shape. It is usually forked or rounded but not as elaborate as the fantail of guppies.

Dorsal Fin:

- Guppies: Female guppies typically have a small and rounded dorsal fin. It is located towards the middle of the back and is not particularly prominent.

- Mosquito Fish: Mosquito fish females have a larger and more noticeable dorsal fin. It is placed further back on the body, closer to the tail, and may have a slight indentation at the top.

Patterns:

- Guppies: Female guppies often display different patterns on their bodies, such as spots, stripes, or intricate markings. These patterns can vary widely between individuals.

- Mosquito Fish: Mosquito fish females usually have a more uniform coloration without prominent patterns. They may have some mottling or faint stripes, but these markings are generally less striking compared to guppies.

Anal Fin:

- Guppies: Female guppies have a smaller and less noticeable anal fin compared to males.

- Mosquito Fish: Mosquito fish females have a larger and more prominent anal fin that may extend further towards the tail.

By observing these differences in size, body shape, coloration, tail shape, dorsal fin, patterns, and anal fin, you can distinguish between female guppies and mosquito fish with reasonable accuracy.