Potassium permanganate is an oxidizing salt compound historically used to disinfect drinking water. When poured into water, potassium permanganate reacts with all organic matter it comes into contact with including parasites. It is effective in killing mosquitoes in stagnant bodies of water. And, if used in small enough amounts, it can even be used safely around pond fish. But be careful when handling it. Potassium permanganate is a powerful oxidizer and it will stain anything it touches–including your skin–a dark brown color.
Calculate the amount of potassium permanganate needed. For large bodies of water, multiply the surface area of the body of water by its depth or average depth. This will give you its acre-footage. To kill mosquitoes, you will need 5.4 pounds of potassium permanganate per acre foot. For small ponds or containers of water multiply surface area by depth. Then multiply that number by 7.5 and divide by 1,000. The result equals the number teaspoons of potassium permanganate you need to add to the water to kill mosquitoes.
Measure the required amount of potassium permanganate into a large container. Then mix it with at least twice the amount of water by volume.
Spread potassium permanganate evenly over the surface of the water. If the amount of potassium permanganate is so large that it must be split into separate containers, be sure to spread each portion evenly over the surface of the water. In bodies of water that are larger than one acre, the best way to apply the chemical is to put the full amount into a large container attached to a submersible pump. Place the container in a motorized boat, submerge the pump the water and drive the boat over the entire surface water to evenly distribute the compound.