Natural Swimming Pool/Ponds (NSP's) are a chemical-free, low-maintenance alternative to traditional chlorine pools. The water is clean, crystal-clear, and filtered naturally using a built-in biological filter.
There are no chemicals to buy, minimal electricity costs (one pump), and no PH level monitoring. If needed, the bio-filter can be supplemented with an automated skimmer or UV sanitizer. As an added bonus, because the wetland is a distinct area, it can be added to an existing pool in a retrofit with minimal additional digging.
Nemo 33 is the deepest indoor swimming pool in the world.The pool is located in Brussels, Belgium. Its maximum depth is 34.5 metres (113 ft). It contains 2.78787 million litres of non-chlorinated, highly filtered spring water maintained at 30 °C (86 °F) and holds several simulated underwater caves at the 10 metres (33 ft) depth level.
Natural pools are closed ecosystems sealed by synthetic pool liners. In addition to mechanical circulation systems, the pools have non-chemical filters to catch additional small particles. The main water-cleaning takes place in the microorganisms and microbes... We need water plants to create a habitat for these elements (that clean the water). http://expandinghorizons.biz/html/pristine_swimming.html#