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Western Mosquitofish

Gambusia affinis

Also called Mosquitofish, Gambusia, Gambezi

SpeciesShort profile

From Southern USA and north-eastern Mexico: the Mississippi River basin from Indiana and Illinois to the Gulf of Mexico and Gulf Slope drainages12

At a glance the quick version

Length4 to 7.5 cm123
Lifespan1 to 3 years21
Sizesmall
Extremely tough and adaptable
Easy to breed, giving birth to live young
Eats mosquito larvae among other small prey
231

Looks how to spot one

Small livebearer (relative of the guppy)

A plain grey little livebearer with rounded fins and an upturned mouth made for feeding at the surface. Females are much bigger and rounder than males and show a dark spot near the vent when carrying young; males have a modified anal fin for mating.23

Coloursplain grey to olive2

Personality what they are like

A bold, quick and competitive little fish that is always ready to feed and can be pushy with tank mates.3

Grooming and care the hands-on bits

A pair can live in a tank as small as about 30 x 20 x 20 cm (12.5 litres). Because it is such a bold, competitive feeder it is best kept in a species-only tank. Import is restricted in the EU, so check local rules.32

Home where they are happiest

Still or slow, plant-rich water. Seriously Fish suggests 18-27 C, pH 6.0-8.0 and hardness 5-30 dH.31

Food basics what goes in the bowl

An omnivore that eats zooplankton, small insects and larvae and detritus; in a tank it takes most foods and enjoys live or frozen brine shrimp and Daphnia.123

Company who they like around

Breeds readily when both sexes are kept together.3

The story where it all began

Native to the Mississippi basin and Gulf coast, the mosquitofish was shipped around the world from the 1920s onward to help control mosquitoes. Today it lives on almost every continent.21

Fun facts for the dinner table

  1. 1

    An adult female can eat hundreds of mosquito larvae in a single day.2

  2. 2

    It can cope with water twice as salty as the sea and temperatures up to 42 C.2

  3. 3

    Young are born live after a pregnancy of about 16-28 days, around 60 at a time.2

  4. 4

    Females can start breeding just weeks after they are born.3

Recognised by the official bits

IUCN Red List
Least Concern (assessed 22 January 2019)1
European Union
Import restricted across the EU2

The care rhythm a typical week and year

A typical home-care rhythm for a Western Mosquitofish. A starting point, not a vet's advice.

Owner questions the things everyone asks

How often should I feed my Western Mosquitofish?

Furry Diary's starting plan is to feed once daily during the warm season. Since they are always ready to feed, be careful not to overfeed. For exact amounts, check the food label and ask your vet. Pet Wiki plan

What does a Western Mosquitofish eat, and what should it never eat?

They are omnivores and enjoy live or frozen brine shrimp and Daphnia, as well as most prepared foods. There is no specific list of foods to avoid in the provided information, so ask your vet or a good breeder for guidance on what not to feed.321

How much space does a Western Mosquitofish need?

A pair can live in a tank as small as 30 x 20 x 20 cm (12.5 litres). Because they are bold and competitive, it is best kept in a species-only tank.32

What temperature, light or water does a Western Mosquitofish need?

They need still or slow, plant-rich water. The recommended temperature is 18-27 C, pH 6.0-8.0, and hardness 5-30 dH. For lighting, no specific info is given, so ask a good breeder or exotic-pet vet.31

How often should I clean a Western Mosquitofish's home?

Furry Diary's starting plan includes a daily pond check, a water test every 14 days, and a filter clean every 30 days. For full cleaning, follow general aquarium guidelines and ask your vet. Pet Wiki plan

Can a Western Mosquitofish live with others?

They are bold and competitive, so they are best kept in a species-only tank. They can live with others of their own kind, and will breed readily if both sexes are present.32

How long does a Western Mosquitofish live?

They typically live for 1 to 3 years.21

Can I handle a Western Mosquitofish?

Handling is not recommended for this fish. It is best to observe them in their tank. If you need to move them, use a net gently.

Written from the sources on this page, a few checked guides (VCA, ASPCA, RSPCA) and Pet Wiki's own starting care plan. A friendly guide, not a vet's advice.

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Where this comes from

Every fact on this page has a numbered source. Spotted an error? support@petwiki.app.

  1. FishBase: Gambusia affinis fishbase.seused for size, max age, native range, water parameters, diet, reproduction, IUCN status
  2. Wikipedia: Western mosquitofish en.wikipedia.orgused for size, appearance, diet, reproduction, lifespan, history, tolerance, EU status, fun facts
  3. Seriously Fish: Gambusia affinis seriouslyfish.comused for tank size, water parameters, diet, behaviour, breeding

Checked 2026-09-30. Text is written in our own words from these sources.