TankBud

Western mosquitofish

Gambusia affinis

FreshwaterFish

Western mosquitofish (Gambusia affinis)
NOZO · CC BY-SA 3.0

Care at a glance

Temperature
64–81°F
18–27°C
pH
6.0–8.0
Adult size
3 in
7.5 cm
Minimum tank
7 gal
25 L
Temperament
Aggressive
Social behavior
Social
Tankmates
With caution
Swim level
Middle
Difficulty
Easy
Breeding
Livebearer · Easy
Rarity
Rare
Family
Poeciliidae
Origin
United States, Mexico

Overview

The western mosquitofish is a tough, adaptable livebearer that suits a species tank better than a gentle community. It is easy to keep, though it has a real aggressive streak.

Did you know

The western mosquitofish has been introduced around the world to eat mosquito larvae. It is such an aggressive competitor that it now harms native fish and amphibians in many places, and it is considered invasive.

Caring for the western mosquitofish

Western mosquitofish are small-bodied, so even a group can live in a tank of 7 gal (25 L) or larger. More space eases squabbling. Give them plants, open water and simple filtration.

They handle a wide range of hard water and cooler temperatures. Keep them at 64 to 81°F (18 to 27°C) with a pH of 6.0 to 8.0. They tolerate cooler water than most tropical fish and do not need heating in a warm room. They eat almost anything, from flake and small pellets to frozen and live foods, and they graze readily.

Western mosquitofish are persistent fin-nippers. Keep them in a species group on their own, or with fast, robust fish that can keep clear of them. Aim for more females than males, and add plenty of plants and cover to spread out aggression.

Females are much larger than the slim males, which fertilize them internally with a gonopodium. The western mosquitofish is a livebearer and is easy to breed. Females can produce brood after brood through the warmer months, so a population builds quickly.

Good to know

The western mosquitofish is a small livebearer in the family Poeciliidae. Its fast breeding is exactly what made it useful for mosquito control.

In the wild

Gambusia affinis is native to the fresh waters of the southern United States and Mexico. It lives in warm, still and slow-moving waters such as ponds, ditches and stream margins.

Common questions

What size tank does a western mosquitofish need?

A western mosquitofish needs at least 7 gal (25 L). It spends most of its time in the middle.

What temperature and pH does a western mosquitofish need?

A western mosquitofish is comfortable at 64–81°F (18–27°C) with a pH of 6.0–8.0.

What does a western mosquitofish eat?

A western mosquitofish eats almost anything, from flake and small pellets to frozen and live foods. It also grazes readily.

How big does a western mosquitofish get?

An adult western mosquitofish reaches about 3 in (7.5 cm).

How can you tell a male western mosquitofish from a female?

Males are slim and much smaller than females, and they fertilize the females internally with a gonopodium.

How does a western mosquitofish breed?

A western mosquitofish gives birth to live young and is easy to breed. A female can produce brood after brood through the warmer months, so numbers build quickly.

Related species