Natural outdoor pools

Plunging into a British pond requires a considerable amount of courage. A lake or pond is far and away the most fascinating feature of a garden but the thought of swimming in one is rather unpleasant. Maybe it is the fact that you can’t see the bottom, or the tadpoles, or the weeds ? but there is something about British ponds that has persuaded thousands of Brits to opt for bright blue alternatives with crystal clear chlorinated water.

But in an age where eco design and sustainability are at the forefront of many minds, an increasing number of people are exploring the concept of the natural swimming pool. ‘There is still a huge lack of knowledge,’ claims David Nettleton, Director of Clear Water Revival. ‘Natural swimming pools are not wildlife pools.’ So no water rats or grass carp, but how clean is the water? ‘It is crystal clear,’ Mr. Nettleton assures, ‘natural swimming pools can be as clean as conventional pools. Swimming in natural fresh water is a far more exhilarating experience than swimming in a chlorine filled box.’

Natural swimming pools were popular in Victorian England but Mr Nettleton first came across the concept in Austria. Being a trained aquatic ecologist, the natural pool encompasses everything he is fascinated in. ‘I could see immediately that the pools are really viable and may potentially overtake conventional chlorine pools as the most popular choice,’ he explains. Designed to fit in with the surrounding landscape, the pools are breathtakingly beautiful and extremely cheap to run.

According to Mr Nettleton, natural pools can be heated either by solar panels or by a conventional heating system which guarantees a water temperature of 28°C. The liners are made of environmentally friendly material without the harmful by-products of normal swimming pool liners. ‘The eco liners are either olive green or slate blue,’ Mr Nettleton says. ‘They are bright colours but blend extremely well with the natural surroundings. I am trying to break the industry from its rut of ’80s Hollywood design and dependence on chlorine.’

Ideally, natural pools should be positioned in a sheltered part of the garden, out of the wind and they should have at least six hours of sunlight. This is to make sure that the reed bed works properly. The living filter (reed bed), which replaces pool chemicals, is separate from the swimming area of the pool but the retaining structure is made of natural materials and is obscured under the surface of the water.

‘We feel it is very important to ensure this artificial structure within the pool is as indistinct as possible, so you will really feel you are swimming in a natural spring. However, we are also able to design more ‘architectured’ or formal pools where such linear features will be used to give the desired effect,’ says Mr Nettleton. The reed bed is a shallow area containing a permeable substrate where friendly bacteria, reeds and nutrient hungry aquatic plants filter the water. ‘It is basically a process of transforming the nutrients in the water from toxic substances which algae feeds on to something it is unable to feed on.’

The pools take three weeks to construct and Mr Nettleton will monitor water quality for the first year. Existing ponds and swimming pools can easily be converted into natural swimming pools with the addition of an adjoining basin to house the living filter.

For more information please visit For more on the subject, read Ptolemy Dean’s article on outdoor swimming pools.