The mosquito fish

The ubiquitous Mosquitofish (commonly Gambusia affinis or holbrooki) is praised by some and damned by others, but none-the-less is sought after by some aquarists. The more common of the Gambusia species is G. affinis which has been widely introduced for mosquito control. The other Gambusia species are much more regionalized like G. holbrooki on the East Coast, G. amistadensis, G. gaigei, G. geiseri, G. georgei, G. heterochir, and G. senilis in Texas, G. noblis in Texas and New Mexico, and G. rhizophorae in Florida and Cuba.

Although the name Gambusia means worthless they are far from worthless, but their ability to control mosquito larvae better than other native fish species is most likely exaggerated. The key to Gambusia’s success lies in its adaptability. The mosquitofish can live in fresh or brackish water with low oxygen levels and in minimal amounts of water. They also adapt well to extremes in water temperatures.

In the aquarium, as in nature, Gambusia eat just about anything including flake food, vegetable matter, and their own young. They are aggressive and will nip the fins of other slower moving fish. As stated above they are very tolerant of a wide variety of water conditions and temperature fluctuations. One of the best things they have going for them is their resistance to disease.

Not a pretty fish, the Mosquitofish, is grayish-green color with females having a dark bar under the eyes and spots on the caudal fin. Some male G. holbrooki have been found in mottled or melanistic form which is very striking. Females grow approximately 2 1/2 to 3 inches while the males rarely exceed 1 1/2 inches.

Water changes seem to spark breeding behavior, but many people find these fish frustrating to breed. Under the right circumstances females produce fry once a month. Gambusia, like other livebearers, are capable of having several spawnings from one mating. Plants are important by providing the babies a place to hide and the adults some variety in their diets.

I have collected Gambusia in creeks, rivers, ponds, bogs, and found them as “feeders” in Pet stores. In the wild they prefer plants or shallows where they can hide from predators which are many considering their size. The Mosquitofish is abundant just about anywhere it is found.

For those who are looking for a challenge Gambusia can be the perfect fish. Caution should be used in keeping them in a community tank. I would recommend a species tank for the sake of all fish concerned and for your sanity.

by David L. Hall