Health officials hope mosquitofish will reduce mosquito-borne diseases

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Mosquitofish in a container. (Photo by David McNew/Getty Images)

SAN DIEGO — They’re tiny. They’re ravenous. And they just might be a mosquito’s worst nightmare.

Mosquitofish can help keep mosquito populations down and reduce the chance they can transmit diseases by gobbling up larvae as fast as mosquitoes can lay their eggs in water, San Diego Environmental Health officials said.

Set loose in ornamental ponds, fountains, bird baths, neglected swimming pools and even horse troughs, mosquitofish go to work to keep mosquito eggs from becoming full-grown, blood-sucking, disease-spreading adults.

San Diego County’s Department of Environmental Health has raised and given out thousands of the hungry little guys to the public for free at dozens of locations around the county over the years.

“We always get a huge number of calls for them, starting in spring,” said Steve Rivera, the County vector control supervisor who oversees the mosquitofish program. “They’ve proven to be very popular over the years.”

The fish are loaded into 45-gallon trash cans or smaller buckets, put onto flat-bed trucks and taken to locations where they are made available to the public.

Rivera said people generally need only two or three fish to get themselves started, and that they come with relatively easy instructions.

For example, when people first bring mosquitofish home, they should allow the fish to get used to their new surroundings by placing the plastic bag containing them into the new water source, whether that’s a pond, pool, bird batch, etc. Wait about 15 minutes to allow the water in the bag to become the same temperature as the pond or pool water — then release the fish from the bag.

Mosquitofish will live alongside other types of fish in ponds. But you should give them some rocks or vegetation to hide among if the other fish are bigger.

Because mosquitofish don’t just eat mosquito larvae and are not native to California, the County instructs people to use them only in manmade water sources and not to put them into natural habitats like lakes, streams or creeks where they can disrupt ecosystems.

You can get mosquitofish at Walter Andersen Nursery in Point Loma, Aquatica in San Marcos, Joe’s Country Feed and Pet store in Valley Center, and the Reef and Reptile Company in Chula Vista.  Click here for additional locations.