The Contra Costa Mosquito and Vector Control District says the fish can help homeowners with pools and ponds and reduce mosquito breeding.
Mosquito fish are a type of guppy that eat mosquito larvae and survive in any habitat, including abandoned or neglected swimming pools.
Areas of Antioch, Brentwood and Oakley have been reported as high-risk areas for humans to contract West Nile Virus.
Residents can now pick up the mosquito fish at the Antioch Corporation Yard on West 4th Street. It's open Monday through Friday from 7:00 a.m. to 4:00 p.m., excluding holidays.