Mosquitofish provided by the County of Santa Clara Vector Control District are intended for mosquito control only and should not be introduced into potential mosquito breeding sources by anyone other than the certified mosquito control technicians.
The District provides FREE mosquitofish to all of Santa Clara County residents for placement in manmade locations such as:
- Ornamental ponds
- Unmaintained swimming pools/ jacuzzi
- Watering trough
- Rain barrels
Mosquitofish (Gambusia affinis) are small fish in the guppy family that are natural predators of mosquito larvae and pupae, making them an environmentally friendly alternative to mosquito control without the use of chemical insecticides. This method is referred to as biological control and is part of our integrated pest management program (IPM).
Gambusia are easily maintained and have a broad tolerance to a wide range of environmental conditions such as poor food supply and temperature changes. Mosquitofish are compatible with most ornamental pond fish such as goldfish, koi, and carp but live best with fish their own size, as larger fish might eat them.
Males are slimmer than females and grow to a maximum length of 1.5 inches. Females have a larger body than males, give birth to live young, and grow to a maximum length of 2.5 inches. Fry are only ¼ inch in size and reach sexual maturity in six to eight weeks. The small size of mosquitofish allows them to inhabit shallow waters and penetrate dense vegetation where mosquito larvae and pupae tend to hide.
Mosquitofish live between two to three years and maintain population levels that fit their environment. Overbreeding is of no concern with mosquitofish.
While mosquitofish are a hardy species, water temperature and water quality must be considered before adding them to a new environment. Take the following steps to help ensure your mosquitofish survive in their new environment.
Treat Tap Water with A Water Conditioner
Mosquitofish cannot survive in water that is treated with chlorine or chloramine. Following the label, treat tap water with a water conditioner sold at your local pet store. Make sure the water conditioner treats chlorine, chloramines, and ammonia.
Help Them Acclimate to Their New Environment
Fish will be given to you in a plastic bag. When you get home, immediately float the bag in the pond, fountain, etc. Wait 20 minutes before releasing into the new environment.
Fish prefer sunlit areas and do not thrive well in heavily shaded locations. Provide large rocks and vegetation for shelter and to help hide from predators such as raccoons and opossums.