The County of San Diego Vector Control program raises and distributes
mosquitofish, also known as Gambusia affinis. These small,
freshwater fish eat mosquito larvae and are available to residents and
locations throughout the County, free of charge.
- Help control backyard mosquito breeding in neglected or
"green" swimming pools, fountains, ponds, and birdbaths,
as well as animal troughs, and other standing water sources.
- Provide an effective and natural method of backyard mosquito
- Aid in reducing the mosquito population, which promotes healthier and safer communities
Female mosquitoes lay their eggs in standing water sources. When the eggs hatch, they become mosquito larvae. Larvae can mature into biting adult mosquitoes in as few as 5 days. Under ideal conditions, mosquitoes can complete their life cycle from egg to adult in as few as 7 days.
CONTROLLING MOSQUITO LARVAE
Adult female mosquitoes bite humans and animals and can spread diseases such as West Nile virus, malaria, and several types of encephalitis. Controlling mosquito larvae limits the number of adult mosquitoes and lessens the chance of getting bit by mosquitoes that spread diseases.
Caring for Mosquitofish
Let your mosquitofish get used to their new home. Keep them in their container and place it directly into the pond for 15 minutes. Wait until the pond and the container's water reach the same temperature. Then release the fish into the pond. After that, mosquitofish need little to no care.
No Mosquitofish in Natural Waterways
Mosquitofish should never be placed in a natural habitat such as lakes, streams, rivers, or creeks; they can destroy natural species and disrupt the ecological balance.
During warm months mosquitofish usually do not need to be fed. However, you must feed the fish if the water source does not have any plant life. Give them fish food flakes and feed them as much as they can eat in 5 minutes, twice a day.
Mosquitofish tolerate water temperatures between 33°F and 104°F, but prefer temperatures around 80°F. Ideally, water should have a pH between 6.5 and 8.0. Keep chlorine, garden insect sprays, and yard chemicals out of their water.
LIVING WITH OTHER FISH
Mosquitofish are compatible with most ornamental pond fish of about the same size. If the mosquitofish are living with larger fish (who may eat them), they need hiding places like rocks and vegetation.
Mosquitofish give birth to live young, rather than laying eggs. Fish live for about 1 year and start eating mosquito larvae at birth. Mosquitofish do not overbreed and maintain population levels that fit their environment.
How Many Fish do I Need?
- Small sources, such as fountains or troughs: 2-3 fish
- Ponds with surface area less than 200 square feet: 3-5 fish
- Larger sources: 1 fish for every 20 square feet of surface area