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Mosquitofish

Gambusia affinis

Freshwater North America Usually captive bred

An exceptionally rugged livebearer with plain silver-grey coloration and an aggressive appetite for insect larvae. Although resilient across broad temperature and water ranges, its pugnacious fin-nipping makes it a poor match for gentle community species. Never release them outdoors due to their severe invasive potential.

Also called: Live-bearing tooth-carp, Mosquito fish.

5 cm adult length, drawn to scale. torpedo body.

Try it in the planner Opens a tank sized to its minimum with 1 fish added.

What it needs

ItemValueBecause
Adult length 5 cm Used for the Space check: the tank must be long enough for the fish to turn round.
Smallest tank 50 L, at least 45 cm long estimated The least water and floor length this species is kept in for good, as a single fish or smallest group.
Extra water per added fish 5 L estimated What each further fish adds once the minimum is met.
Waste load Class 1 of 5 estimated How much waste an adult makes against its size. Feeds the Load check.
Temperature 12 to 28 C Stock sharing a tank need overlapping ranges.
pH 6.5 to 8 Compared with tankmates in the Water check.
Hardness GH 8 to 25, KH 4 to 15 Degrees of general and carbonate hardness.
Flow Low Low-flow fish are stressed in a strong current.
Light Moderate Matched to the lighting class on the needs sheet.
Group size Single fish is fine Not a schooling species.
Temperament Semi-aggressive Territorial: weak.
Swims in Upper water Fish that use different levels share a tank more easily.
Lifespan About 3 years A fish is a long commitment.
Experience Suits a first tank A guide to how forgiving the species is of mistakes.
Jumps Yes Keep the tank covered.

Tags marked estimated are judged from the size and habits of the species rather than measured, so treat them as a sensible default.

Diet and tank layout

Mosquitofish is an carnivore that swims in the upper water. It is safe with plants. Give it some cover. It will eat fish small enough to swallow. It nips fins.

Tankmates

Works with

Depends

Avoid

Compare any two fish on the compatibility page, or print the equipment for a stock on the needs sheet. How this is worked out: the method.