The Garden Guide

Natural Swimming Ponds

Natural swimming ponds do not use the complex technology of chemical sterilization and filtration. Instead, they use nature's infinitely more sophisticated technology: ecological balance. As in a natural lake, micro-organisms break down organic matter into materials which plants can use as nutrients.

The use of natural processes in artificial swimming pools was pioneered in Austria (c 1985) by Peter Petrich and a company called Biotop. Since then, the principle has been widely used in continental European homes, hotels and resorts. The swimming pools are ecologically balanced, self cleaning and beautiful. Instead of worrying about whether chlorine is damaging their eyes and mucus membranes (possibly aggravating asthma and nasal congestion), swimmers can feel confident in doing what their ancestors have done since prehistoric times: swimming in fresh clean water.

Design principles for natural swimming ponds

  1. Pool Area - natural ponds are larger than chemically treated pools (eg swimming area of 25 sq metres and a biological area of 25 sq metres). One or two walls of the pool will rise above the water surface to allow access for swimmers. The other walls (between the swimming and planted areas) will be 100mm below the water surface.
  2. Swimming Zone - a deep swimming area (1.5 to 2.5m). This zone can be walled and tiled (and cleaned with a normal pool bottom cleaner).
  3. Regeneration Zone - a marginal area planted with aquatic and semi-aquatic plants. This area needs to be at least as large as the swimming zone. The aquatic plants grow in shingle (without topsoil) so that they are forced to take their nutrients from the water. Pruning and removing plants (usually in winter) takes nutrients out of the pond.
  4. Pump Chamber - the pump (1) draws water through the Regeneration Zone (2) draws water from the surface of the pool, to remove floating debris (3) returns the water to the Swimming Zone, after filtration.
  5. Heating - if the pool is heated the plants will grow faster than normal and will have to be thinned from time to time.
  6. Drainage Ditch - the pood is surrounded with ditch to keep out surface water runoff (which would introduce nutrients and affect the ph of the water)

Cost note: costs tend to be higher for natural swimming pools than for conventional swimming pools. See pond construction notes

Natural swimming pond