Annually, after I repot the aquatic plants, the pool briefly turns green as the algae eat stirred-up nutrients. That's why you must never change the water. If you do, the pond must achieve its natural balance all over again. Their starlike flowers are bright and magical as they float serenely on the water's surface. I grow tropical and hardy water lilies.
Most flowers are lavender, purple, or fluorescent pink.
Some bloom at night. Most tropical lilies spread widely. In my garden, this variety stays in the pool all year. I repot them only every few years because they don't spread like the hardy lilies, though they bloom just as profusely. Where winters are cold, treat tropicals as annuals.