This species is on the Spanish Catalogue of Invasive Alien Species (Royal Decree 630/2013): keeping, transporting and trading it are prohibited in Spain.
This species is on the Union list of invasive alien species of Union concern (Regulation (EU) 1143/2014): keeping, transporting and trading it are prohibited in the European Union.
Description
Gambusia holbrooki is the eastern mosquitofish, a livebearer of 4 to 5 cm, from the Atlantic and Gulf coasts of the United States, that has been spread across half the world. It was released to fight mosquitoes, and it is today an invasive alien species in Spain and in the European Union: it is on the Spanish Catalogue (Royal Decree 630/2013), which generally prohibits possessing, transporting, trafficking and trading it, and on the Union List. It is described here to identify it, not to recommend it.
Its effectiveness against mosquitoes is in doubt and in Europe it is blamed for a serious threat to endemic species. A specimen is never released into the wild, and before thinking of keeping one you must find out about the rules that apply in your case.
Behavior
It has a reputation for being more aggressive than other small livebearers and for eating invertebrates voraciously. In the wild it is seen in shoals at the edges of the water, always near the surface.
It lives well with large, robust hard-water fish, although its invasive status makes keeping it inadvisable in Spain and the European Union.
Avoid housing it with small or long-finned fish, shrimp and small snails, and with any native species: it is never mixed with them or released.
Habitat
Gambusia holbrooki is native to the Atlantic and Gulf slopes, from New Jersey to Alabama. It lives in still or slow-flowing water, above all in vegetated ponds and lakes, backwaters and quiet stream pools, and it also frequents brackish water. It is seen shoaling at the edges.
It was introduced worldwide to fight mosquitoes and is established throughout southern Europe.
Details
🌊 Water parameters
🐠 Minimum tank size
Breeding
A livebearer with a fecundity that explains why it is so invasive: it matures at four to six weeks, can produce up to three generations in a year, and gestation lasts three to four weeks. The brood is usually forty to sixty young, and can reach 354.
A population that escapes multiplies fast. Surplus young are never released or flushed down the drain.
Diet
Adults eat small terrestrial insects, usually taken in the drift and among aquatic plants, and they select very small prey. They have also been seen taking mosquito larvae.
- Staple: small animal prey, live or frozen.
- Supplement: fine flakes or pellets.
What about your tank?
Enter your tank's values to see only the compatible species that fit them. Litres apply to fish.
Compatible fish
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7.5 and 22–27 °C.
They share water: pH 6–8 and 23–30 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–8 and 20–26 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–7 and 23–30 °C.
They share water: pH 6–7 and 23–30 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7–8 and 26–30 °C.
They share water: pH 6–7.8 and 20–25 °C.
They share water: pH 6–7 and 20–28 °C.
They share water: pH 6–7 and 24–26 °C.
They share water: pH 6–7.5 and 22–27 °C.
They share water: pH 6–7.5 and 22–27 °C.
They share water: pH 6–7.5 and 22–27 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–8 and 22–26 °C.
They share water: pH 6–7 and 24–27 °C.
They share water: pH 6–8 and 21–26 °C.
They share water: pH 6–8 and 20–30 °C.
They share water: pH 6–8 and 24–30 °C.
They share water: pH 6–7.5 and 25–30 °C.
They share water: pH 6–7.5 and 24–30 °C.
They share water: pH 6.5–8 and 24–26 °C.
They share water: pH 6–8 and 22–26 °C.
They share water: pH 6–7.5 and 20–25 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6.5–7.5 and 18–24 °C.
They share water: pH 6–7 and 27–30 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–8 and 22–27 °C.
They share water: pH 7–8 and 18–28 °C.
They share water: pH 6.5–8 and 22–28 °C.
They share water: pH 7.5–8.2 and 26–28 °C.
They share water: pH 6–7.5 and 25–28 °C.
They share water: pH 6–8 and 22–28 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7.5 and 26–30 °C.
They share water: pH 6–7 and 23–28 °C.
They share water: pH 6–7.5 and 23–28 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–7.5 and 24–27 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 6–7 and 24–30 °C.
They share water: pH 6–7.5 and 22–26 °C.
They share water: pH 7.5–8.5 and 24–28 °C.
They share water: pH 7.5–8.5 and 24–28 °C.
They share water: pH 6–7 and 20–26 °C.
They share water: pH 6–6.5 and 23–27 °C.
They share water: pH 6.5–7.2 and 22–26 °C.
They share water: pH 6–7.5 and 20–26 °C.
They share water: pH 6.5–7.5 and 22–26 °C.
They share water: pH 6.5–7.5 and 22–26 °C.
They share water: pH 6.5–7.5 and 22–26 °C.
They share water: pH 6–7.5 and 24–28 °C.
They share water: pH 6–8 and 25–35 °C.
They share water: pH 6–8 and 15–22 °C.
They share water: pH 6.5–8 and 15–24 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 6–7 and 23–28 °C.
They share water: pH 6–8 and 21–27 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 7–8 and 20–26 °C.
They share water: pH 6–7.2 and 22–28 °C.
They share water: pH 7–8 and 22–27 °C.
They share water: pH 7–8.2 and 15–26 °C.
They share water: pH 6–7.2 and 22–26 °C.
They share water: pH 6–7.2 and 24–28 °C.
They share water: pH 6–7.2 and 24–28 °C.
They share water: pH 6–7 and 26–30 °C.
They share water: pH 6–7.5 and 22–28 °C.
They share water: pH 6–7 and 22–26 °C.
They share water: pH 6.5–7.5 and 22–26 °C.
They share water: pH 6–8 and 25–29 °C.
They share water: pH 6–6.5 and 24–28 °C.
They share water: pH 6–7 and 24–28 °C.
They share water: pH 6–7 and 23–28 °C.
They share water: pH 6–8 and 23–27 °C.
They share water: pH 6–7.2 and 20–28 °C.
They share water: pH 6–7.5 and 23–28 °C.
They share water: pH 6–8 and 24–28 °C.
They share water: pH 6–7.5 and 20–26 °C.
They share water: pH 6–7.5 and 23–27 °C.
They share water: pH 6–8 and 22–26 °C.
They share water: pH 6–8 and 22–28 °C.
They share water: pH 6–8 and 24–27 °C.
They share water: pH 6–7.5 and 22–27 °C.
They share water: pH 7–8 and 22–28 °C.
Compatible invertebrates
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 7–8 and 20–28 °C.
They share water: pH 6–6.5 and 20–24 °C.
They share water: pH 6.5–7.5 and 22–27 °C.
They share water: pH 7–8 and 18–25 °C.
They share water: pH 7.5–8.5 and 24–29 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 7.5–8.5 and 26–30 °C.
They share water: pH 7–8.5 and 22–28 °C.
They share water: pH 7–8.2 and 20–28 °C.
They share water: pH 6.5–7.5 and 20–26 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 6–6.8 and 20–24 °C.
They share water: pH 6–6.8 and 20–24 °C.
They share water: pH 6.5–7.5 and 18–27 °C.
They share water: pH 7.5–8.5 and 27–30 °C.
They share water: pH 6.5–7.5 and 22–28 °C.
They share water: pH 7–8 and 18–28 °C.
They share water: pH 6.5–7.5 and 23–28 °C.
They share water: pH 6.5–7.5 and 23–28 °C.
They share water: pH 7.5–8.5 and 27–30 °C.
They share water: pH 7–8 and 23–28 °C.
They share water: pH 7–8 and 20–28 °C.
They share water: pH 6.5–7.5 and 18–26 °C.
They share water: pH 6.5–7.5 and 18–26 °C.
They share water: pH 6.5–7.5 and 18–26 °C.
They share water: pH 6.5–7.5 and 18–26 °C.
They share water: pH 6.5–7.5 and 18–26 °C.
They share water: pH 6.5–7.5 and 18–26 °C.
They share water: pH 7–8.5 and 22–28 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 7–8 and 22–28 °C.
They share water: pH 6.5–8 and 15–28 °C.
They share water: pH 7–8 and 15–28 °C.
They share water: pH 7–8.5 and 18–28 °C.
They share water: pH 6–6.5 and 18–24 °C.
Sources
- FishBaseFroese, R. and D. Pauly. Editors. 2026. FishBase. World Wide Web electronic publication.
- Real Decreto 630/2013Real Decreto 630/2013, de 2 de agosto, por el que se regula el Catálogo español de especies exóticas invasoras. BOE n.º 185, de 3 de agosto de 2013. Consultado 2026-10.
- Reglamento UE 1143/2014Reglamento (UE) n.º 1143/2014 sobre la prevención y la gestión de la introducción y propagación de especies exóticas invasoras. Consultado 2026-10.
- Reglamento de Ejecución UE 2022/1203Reglamento de Ejecución (UE) 2022/1203, que añade a Gambusia holbrooki a la Lista de la Unión de especies exóticas invasoras. Consultado 2026-10.
The care values (pH, temperature and hardness) come from a single source: none of the other accepted sources records them for this species.
Water: FishBase gives pH 6-8.8, hardness up to 40 dH (no minimum) and 15-35 °C. The profile's hardness minimum (5 dGH) is its own judgement and does not come from any source. Seriously Fish has no profile of the species (404). Size: 4.7 cm TL in FishBase, for males or unsexed. Breeding: maturity at 4-6 weeks, up to three generations a year, gestation of 3 to 4 weeks and a brood of usually 40-60 young, up to 354. Behaviour: no cited source describes it for the species; the aggressive marking is the profile's own judgement, supported by the Seriously Fish profile of Heterandria formosa (https://seriouslyfish.com/species/heterandria-formosa/), which calls the genus Gambusia «much more aggressive». Effect in Europe: FishBase notes that introductions to Europe have seriously threatened many endemic species and that it is now accepted that its effect on mosquitoes has been minimal. Name: «gambusia» is the chosen name (the one in Royal Decree 630/2013); FishBase calls it «Eastern mosquitofish». Invasive: it is on the Spanish Catalogue of invasive alien species (Royal Decree 630/2013, annex: «Gambusia holbrooki Girard, 1859. Gambusia») and on the Union List (Implementing Regulation (EU) 2022/1203, which adds it to the species of Regulation (EU) 1143/2014).
Litres per fish, tank sizes and lifespan: the profile's own judgement. The sources consulted do not give them.
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