An alternative to chlorine pools, the BioTop Natural Pools use plants to keep water clean and clear. A natural swimming pool is a system consisting of a constructed body of water, where the water is contained by an isolating membrane or membranes, in which no chemicals or devices that disinfect or sterilize water are used, and all clarifying and purifying of the water is achieved through biological filters and plants rooted hydroponically in the system. Natural Pools provide crystal clear water without any use of chemicals. The natural pool creates the incomparable feeling of swimming in natural water.
The swimming zone should be physically separated from the regeneration and should reach a depth of 2 m (6 ft 6 in) in swimming ponds. The regeneration zone and swimming zone must be equal in area for sufficient purification. The swimming portion of the pool can look like a conventional swimming pool or a natural pond. The regeneration zone can be placed adjacent to the swimming area or in a remote location depending on the space available. In modern natural swimming pools there is no minimum depth for the swimming zone and the regeneration zone can now be reduced greatly and in some cases is non existent. Clear Water Revival was the first company to build indoor natural swimming pools in the UK. In these pools a regeneration zone can be used outside the building or a natural filtration chamber can be built without a planted area indoors.