Algae are single-celled plants that contain chlorophyll. They are some of the hardiest and most widespread organisms living on the planet today. They’ve had a long time to evolve and adapt. Scientists tell us they were one of the very first life forms on the planet. Now there are more than 30,000 different types of algae. Their seeds, called spores, are constantly dropped in swimming pools by rain, wind, leaves, and other debris. It doesn’t take much to make algae happy. Give it warm water, sunlight, and carbon dioxide and it will thrive. And algae love pool owners who allow their pool water to sit stagnant for hours. There is no need for stagnant water today with an ultra-efficient pool pump that circulates pool water 24/7.