a couple of months back i had a problem with mosquito's breeding under my back porch where the landlord allows the water from the washing machine to drain. i used someones suggestion of water softener salt. it has worked like nothing else i have tried. our porch went from unbearable to even walk out to do laundry, to being able to hang on the back porch with no more than a couple of bugs here and there. i think that the salt is the least harmful way for the environment, but i could be wrong. so to anyone with the same sort of problem, a 40# bag of salt cost 5 buks at the store. almost every mosquito is gone. thanks everyone just wanted to update with results