If you spray pesticide in them you have to come back every few weeks. Many communities have found a biological answer.
The Gambusia affinis is commonly known as
the "mosquito fish" because of its healthy appetite for the larvae of the irritating and disease-spreading insects. Lately, the fish is being pressed into service in California, Arizona, Florida and other areas struggling with a soaring number of foreclosures.
The problem: swimming pools of abandoned homes have turned into mosquito breeding grounds.
"They are real heroes," says Josefa Cabada, a technician at the Contra Costa Mosquito & Vector Control District, a government agency. "I've never seen a mosquito in a pool with mosquito fish."
The mosquito fish is well suited for a prolonged housing slump. Hardy creatures with big appetites, they can survive in oxygen-depleted swimming pools for many months, eating up to 500 larvae a day and giving birth to 60 fry a month.