Algae are green or brown plants that grow around water. Algae grow in water coolers that have been left alone, usually in the heat for too long. Algae can be removed easily with bleach, which is fatal to algae. Humans should not drink or eat algae as that can cause illness. A rough scrub brush forces the algae off of surfaces and breaks it up into smaller pieces. The algae can get stuck to the brushes, so use a sponge to wipe the surface clean.
Rinse out the water cooler with a hose. Use the nozzle on the hose to spray off loose algae. The nozzle creates high water pressure, which loosens and removes some of the algae.
Pour bleach inside the cooler. Fill it about a fourth of the way full. As you pour in the bleach, let some of it run down the inner sides of the cooler.
Put on gloves. Rubber kitchen gloves work well.
Dip the scrub brush into the bleach and scrub the algae.
Wipe down the sides with a sponge and bleach.
Dump out the bleach.
Rinse out the cooler. Rinse it two or three times to make sure all the bleach is gone. Set it out in a sunny spot to dry or towel dry it. Rinse out sponges and scrub brushes.