Eastern Mosquitofish

Gambusia holbrooki, the Eastern Mosquitofish, is a small, robust livebearer native to the eastern United States from New Jersey to Florida. It is best known for its appetite for mosquito larvae and has been introduced worldwide for biological mosquito control — a practice now viewed with ecological concern due to its aggressive predation on native amphibians and small fish.

In the aquarium, Eastern Mosquitofish are fascinating to observe and incredibly hardy — tolerating temperatures from near-freezing to over 35°C, salinity ranges from fresh to brackish, and severely degraded water quality. They are surface dwellers that target anything moving near the water surface.

Despite their hardiness, Gambusia holbrooki are notoriously aggressive toward other fish, particularly soft-finned species, and are best kept in a dedicated species tank or outdoor pond. Males are very much smaller than females.

Water: 14–28 °C, pH 6.5–8.5, fresh to brackish; extraordinarily tolerant of poor conditions. Tank: 60 L species tank; surface plants appreciated; secure lid as they jump; outdoor tub or pond suitable. Feeding: Mosquito larvae, live Daphnia, Artemia, and surface-floating flake; insectivore diet preferred. Breeding: Very prolific; females produce 10–60 fry regularly; fry immediately independent. Compatibility: Species tank only; aggressive fin-nippers that harm most community fish.