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Contra Costa County residents may request mosquitofish from the District online or by calling 925-685-9301.

Upon request, the District will inspect your water feature and determine if mosquitofish are appropriate to address the mosquito issue on the property. If fish are an appropriate option, the District employee will place the fish in the water feature.

Mosquitofish (Gambusia affinis) are live-bearing freshwater minnows related to guppies. These small fish (1-2 inches in length) are top swimmers that feed on insects and wind-blown organic debris at the surface of the water. They have a voracious appetite. An adult can eat hundreds of mosquito larvae a day! This makes them an excellent biological tool for mosquito control, as the fish gobble up the mosquito larvae before they have a chance to develop into flying, biting adult mosquitoes.

May contain: animal, sea life, and fish

Biological Control

As a natural predator of mosquito larvae, mosquitofish have been used for mosquito control purposes throughout the world for many years. More than 100,000 of these fish are produced each year at the District's mosquitofish production facility. 

May contain: animal, sea life, and fish

 Mosquitofish Care

Detailed information regarding the proper care of mosquitofish.


 How to Get Mosquitofish

Fish Net

PLEASE NOTE: Please make requests for mosquitofish through the District voicemail at 925-685-9301 or online. You must be a resident of Contra Costa County to receive mosquitofish. Once a request has been made, a District employee will inspect the property and if mosquitofish are necessary and appropriate, the employee will place the mosquitofish in the Contra Costa County water feature associated with the request.