Summit 2 Pack Mosquito Dunks are a biological mosquito control that kills mosquitoes before they're old enough to bite. Simply place the dunk in a water garden or any standing water, and it will keep working for 30 days or more. The dunks are completely biodegradable and are safe for use around birds, fish, wildlife, and pets. Each dunk treats up to 100 square feet of surface water, regardless of depth.