The problem is that the mechanism that bleach uses to kill water-borne things is not the same as will work on mosquito larve.<br><br>Bleach works by the clorine combining with/ burning delicate membranes. In fish this manifests as damaging the gills. For bacteria the clorine "burns" the exposed bacteria. Mosquito larve breath atmospheric air, this is why they live in stagnent water and not agitated water. Agitated water will tend to drown them. Oil floating on the water forms an unbreathable layer over them, and they sufficate.<br><br> Seth