A vexing problem with the foreclosure wave sweeping the nation is abandoned swimming pools are becoming breeding grounds for mosquitoes, which can carry deadly diseases. Now many towns in foreclosure epicenters such as Florida, Arizona and California are turning to a novel solution—stocking the pools with fish known as "mosquito fish" that eat the larvae. The fish can eat up to 500 larvae a month and save the town the expense of repeated spraying of toxic pesticides. The solution is not without its critics. The fish breed are known to harass the California red-legged frog, a threatened species, so towns should be wary not to transfer the fish from swimming pools to local ponds. But many applaud the application of an environmentally sound solution.