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The Mosquitofish 
David L. Hall
813 Williams Ave.
Madera, CA 93637
dahall at lightspeed_net

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 to 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