In the Southwest U.S., the backyard pool was the equivalent of the white picket fence:  a sign the homeowners had achieved middle-class status. But as the foreclosure crisis emptied neighborhoods, the once-gleaming pools  - overflowing with algae are infested with mosquitoes and become hazardous reminders of all that was lost in the sub-prime meltdown.

A spate of forclosures is causing an green pool epidemic.  In one Nevada district the number of "green pool" complaints has jumped to 2,800 in 2008, from about 1,600 in 2007.  This year, the health department received nearly 500 complaints from January through March, an 80% increase over the same time last year.  And there are few signs of complaints trailing off: In the first quarter of 2009, Nevada had the nation's top foreclosure rate, according to RealtyTrac. In Las Vegas and across the West, health officials take measures to keep abandoned pools from breeding mosquitoes and disease.

"As the economy went south, the number of green pools went north," said Chris Conlan, supervising vector ecologist in San Diego County's Department of Environmental Health, which stages weekly helicopter flyovers to spot rancid pools.

Fighting green pools with fish

One afternoon in Las Vegas, Robert Cole approached a 3,215-square-foot house on Bracken Cliff Court, armed with his chief weapon against the mosquito scourge: a container of silvery fish. A "For Sale" sign advertised the pool and spa out back. You could smell them from the frontyard.  In California, Arizona and Florida environmental officials also rely on Gambusia affinis, or mosquitofish. These inches-long creatures can survive for months in stagnant water, and to them, a batch of mosquito larvae is a prime-rib buffet.  In Contra Costa County in Northern California, officials breed up to 2 million fish a year, and some residents bring them home in coffee cans.  About 50 fish are needed to rid a 400-square-foot pool of mosquitoes,

"In the past, you'd just tell homeowners to take care of their backyards," said Craig Downs, the district's general manger. "But in the last two years, nobody's been home."

In Maricopa County, Ariz., which includes Phoenix, authorities are on track to respond to 14,000 pool complaints this year, said John Townsend, vector control division manager. They'll need a sea's worth of fish.  "You get backyard swamps here, and it's no different than in Texas or Louisiana," he said.

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