Bleach is more than just a powerful cleanser; it's also a pesticide. When used with care, a few drops of Clorox bleach added to a birdbath keeps standing water mosquito-free. This treatment kills larvae, which grow in stagnant water. A little goes a long way, though; a tablespoon of bleach to treat 50 gallons of water eliminates pests while keeping feathered friends safe. Never add bleach to natural waterways and ponds.