Do Lily Pads Help Keep Water Clean?

Algae

• Water-lily leaves are broad, approximately 6 to 8 inches in diameter, circular and notched from the leaf's smooth edges to its center. Water lilies do not keep a pond or lake clean in the sense that they decrease water pollution. Rather, with their large leaves floating on the water's surface, water lilies prevent a lot of sunlight from reaching the water's bottom, which decreases the growth of algae, according to the Texas AgriLife Extension Service. Algae can be stringy and also produce green water. It can make the water look dirty and unattractive. More critically, when there is a lot of algae, the water's oxygen level can decrease dramatically, suffocating aquatic life, such as fish.

Leaf Structure

• Water-lily leaves lay flat so they can get enough sunlight for photosynthesis. The interior of water-lily leaves helps the plant and leaves thrive on water surfaces. Inside each leaf is a spongy layer, called the mesophyll layer, that provides water-lily leaves buoyancy. Inside the mesophyll are hard, thick-walled cells, called sclereids, that help to keep the leaf from ripping. Water-lily leaves are sturdy and can be folded over by waves and wind without being damaged.

Decreasing Algae

• To help decrease the growth of algae in a pond, water lilies must cover 50 percent to 75 percent of the water's surface, according to the Texas AgriLife Extension Service. This means planting one water lily for every 10 square feet of surface area.

Planting

• For backyard ponds, where koi and other fish live, the University of Illinois Extension advises planting water lilies in containers in heavy, clay loam soil. One of the most important factors to consider in growing water lilies is temperature. To thrive, tropical water lilies need temperatures of at least 75 degrees Fahrenheit during the day, 65 degrees Fahrenheit at night and at least four hours of direct sunlight daily. Tropical water lilies die with the first hard frost. Hardy water lilies, which are perennials, perform well at temperatures 50 degrees Fahrenheit or higher. During winter, the plant's containers must be lowered under the water to be far away from expected ice formation.