fish · Poeciliidae
Mosquitofish
Gambusia affinis
Wild range: Mississippi River basin from central Indiana and Illinois south to the Gulf of Mexico, and Gulf Slope drainages west into northeastern Mexico; widely introduced nearly worldwide for mosquito control (North America)
At a glance: Mosquitofish care
Compiled reference information. Review the care notes and original sources below.
What temperature is listed for Mosquitofish?
The compiled profile lists 18.0–27.0 °C for Mosquitofish (Gambusia affinis). Check the original sources below for context and differing recommendations.
What tank size is listed for Mosquitofish?
The profile lists a minimum tank volume of 10.0 US gallons (38.0 liters). Volume alone does not establish suitability; consider dimensions, group size and other inhabitants alongside the full care notes.
What pH is listed for Mosquitofish?
The compiled profile lists a pH of 6.0–8.0. Review the cited care sources alongside the other water parameters in this profile.
Natural habitat
Shallow, heavily vegetated margins of still or slow water — ponds, lakes, backwaters, and quiet stream pools; also tolerates brackish conditions (Seriously Fish, FishBase).
Where they are found
Catalog primary name Gambusia affinis (Baird & Girard, 1853) — western mosquitofish — per inventory lock and US pet-trade "mosquitofish". Sister species Gambusia holbrooki Girard, 1859 (eastern mosquitofish) is treated as distinct by Seriously Fish, FishBase, and modern literature (gonopodium serration and dorsal-ray counts differ); a separate inventory row eastern-mosquitofish covers holbrooki. ITIS still lists G. holbrooki as a junior synonym of G. affinis (older standing) — noted only. Synonyms include Heterandria affinis, Gambusia patruelis, Zygonectes patruelis, and others. IUCN Least Concern (assessed 2019). Extremely widely introduced; often invasive and harmful to native fishes/amphibians — never release outdoors; EU list of invasive alien species of Union concern restricts import/release in member states.
Aquarium care
Extremely hardy North American livebearer sold for ponds and mosquito control as much as aquaria. Plan at least a 10 US gallon (~38 L) species tank for a small group (Aquarium Tidings); Seriously Fish notes a pair can physically fit in ~12.5 L, but that is too small for stable water and aggression management. Prefer gently filtered, heavily planted setups with floating cover and a secure lid (jumpers). Aquarium temperature about 18–27°C with pH 6.0–8.0 and GH roughly 5–25 (Seriously Fish, FishBase; outdoor ponds tolerate wider extremes). Not a community fish: hyper-competitive fin-nipper that intimidates smaller/long-finned tankmates and preys on fry and small invertebrates. Best as a species-only tank or outdoor pond stock where legal. Never release into natural waters — invasive almost everywhere introduced.
Feeding
Omnivorous micro-predator: quality flakes or micro-pellets as staple plus frequent live/frozen Daphnia, brine shrimp, bloodworms, and other small invertebrates; will take mosquito larvae and some plant/algae matter (Seriously Fish, FishBase, Aquarium Tidings). Feed small portions; avoid overfeeding in small tanks.
Compatibility
Poor community choice. Notorious fin-nipper and bully of smaller or long-finned fish; will eat eggs, fry, dwarf shrimp, and other tiny tankmates (Seriously Fish, Aquarium Tidings, NANFA primer). Keep species-only, or only with robust similarly assertive fish that can hold their own — and expect bickering among males. Do not confuse with feeder guppies; attitude is the giveaway. Never release outdoors (OSU Extension / invasive-species guidance).
Breeding
Prolific livebearer. Males smaller with a gonopodium; females larger with a gravid spot. Gestation roughly 3–4 weeks (about 16–28 days); broods commonly 10–100. Adults readily eat fry — use dense plants or a separate raising tank. Females can store sperm and produce multiple broods; surplus fry are hard to place in the hobby (Seriously Fish, FishBase, Aquarium Tidings).
Sources
Compiled from multiple independent care sheets — not copied from a single site.