The natural swimming pools are small watery ecosystems. They can be built by using increasing levels of technology according to the requirement of the customer.

The elements always present and those which guarantee a correct filtration of water are:

• the zone of swimming in which there are not the watery plants ;
• the zone of regeneration, major of maximum 1 m, with gravels, watery zeolites and plants which make biological function of filter. Thanks to this not very major zone, water is heated much more easily and reaches major temperatures compared to a traditional swimming pool, by increasing the useful period of swimming ;
• the fall or the brook which ensures the oxygenation of water and its energisation ;
• in more sophisticated installations, one can employ two fed types of material each one by a pump of average or high power, placed in a technical room: the skimmer which allows freedom of movement of surface water, the other, by the tubes of drainage placed under the gravel and the watery plants, which makes it possible to maintain always elevé the level of purification.

The natural processes transform the organic substance present in the swimming pool by the aerobic microfaune (present on the surface of the gravels) into simpler elements such as phosphates and nitrates. Those are absorbed watery plants by the roots and are used for their growth. In more than one system of circulation of water in cicrcuit closed, one can envisage a filter UV for a better washing of water, thanks to the destruction of the algae present when the estival temperatures are high.