mosquito fish

The County of San Diego Vector Control program raises and distributes mosquitofish, also known as Gambusia affinis, to residents and fish distribution locations throughout the county to aid in the control of backyard mosquito breeding.

Mosquitofish are small freshwater fish that eat mosquito larvae. Mosquitoes will breed in many backyard water bodies such as green swimming pools, fountains and ponds. By providing these fish, free of charge, the Vector Control Program is providing an effective and natural method of control, which reduces the mosquito population, and promotes safer communities for all San Diegans. 

Find the nearest mosquitofish distribution location

Mosquito Larvae
Female mosquitoes lay their eggs in standing water sources, such as bird baths and neglected pools. When these 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
Controlling mosquito larvae is important because it limits the number of adult mosquitoes in the area. Adult female mosquitoes bite humans and animals and can spread diseases such as West Nile virus, malaria, and several types of encephalitis. By controlling mosquito larvae, you can lessen your chances of getting bit by mosquitoes that spread these diseases.

Using Mosquitofish
Mosquitofish are ideal for controlling mosquito larvae in backyard ponds, birdbaths, fountains, animal troughs, unused swimming pools, and other standing water sources. Mosquitofish should never be placed in any natural habitat such as lakes, streams, rivers, or creeks. They are greedy eaters, so by placing them into natural waterways, they may destroy natural species and disrupt the ecological balance.

Caring for Mosquitofish
When you get your fish home, let them get used to their new home. Keep the fish in their container and place it directly into the pond for 15 minutes. Wait until the pond and the container's water are the same temperature. Then release the fish into the pond. Once in their new home, mosquitofish need little to no care.

During warm months mosquitofish usually do not need to be fed.  However, you mush 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.

Living Conditions
Mosquitofish can tolerate water temperatures between 33°F and 104°F, but like temperatures around 80°F. They like water with 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. They live best with fish their own size, as larger fish may eat the mosquito fish. If the mosquitofish are living with larger fish, they need hiding places like rocks and vegetation.

Mosquitofish give birth to live young, rather than laying eggs. Each fish live for about 1 year, and begin eating mosquito larvae as soon as it is born. Mosquitofish do not over breed 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
For More Information On 
WNV Or Other Vectors Contact: 
(858) 694-2888
SD Fight the Bite Homepage