Top Quality Pond Mosquito Dunk 6pk. Used by professionals for more than a decade Mosquito Dunks have proven their value in destroying Mosquitoes. By killing the larvae before it matures into a biting adult pest. Made with natural Bti, Mosquito Dunks represent a major breakthrough for people and the environment compared with the traditional toxic chemical approach to mosquito control. Once a month float a Dunk in the Water Garden and every place water accumulates around the home. Each Dunk will effectively treat up to 100 square feet of surface water regardless of depth. Dunks may be broken to treat small areas. EPA registered in all 50 states.