The way a conventional backyard swimming pool works is that you use toxic chemicals to kill any living thing in the water, essentially creating a liquid dead zone.
An Austrian company called Biotop Natural Pool uses plants to keep pool water safe. Instead of killing all life, the Biotop system creates an ecosystem where the pool is teeming with life. Pool designs have separate swimming and plant-growing areas of equal size. The plants eat the algae, which would otherwise take over.