Water lilies are not only beautiful additions to your fish pool, but they are also extremely useful. Water lilies help to control algae growth and provide shade for your fish. Water lilies can also protect your fish from nosy predators that prowl around your fish pool, because the plants can spread up to four feet. When planting a water lily in a small fish pool, you'll want to keep that in mind. Depending on the size of your fish pool, you may want to plant only one or two water lilies so they don't end up covering the entire water surface.
Plant your water lily in a fabric pond pot or a no-hole plastic container. Make sure the pot is 10 to 14 inches in diameter and at least six inches deep.
Fill the pot halfway with a heavy clay loam or a commercial potting mix designed specifically for aquatic plants. Do not use regular potting soil. Add two to four fertilizer tablets (made for flowering aquatic plants) and fill the pot with more soil until it is two inches from the top.
Set the water lily's tuber upright and bury the roots gently into the soil. Do not bury the tip of the tuber.
Add one inch of sand or pea gravel on top to help keep the soil in the container when it's placed into the fish pool. Keep the gravel away from the tuber's crown.
Place the potted water lily into the fish pool, ensuring that the water is approximately six inches over the crown. The lily leaves should be floating at the water's surface. Make sure the water is at least 70 degrees Fahrenheit before planting the water lily.