The idea of "natural" swimming pools with self-cleaning bio-systems originated in Austria, where a green approach to life is more well-established, but there are increasing numbers of British homeowners keen to take the plunge.
Apart from their impressive ecological credentials, natural pools also become an organic part of the surrounding landscape. Some Austrians have turned almost the whole of their gardens into lakes, which look just as magical in the winter when frozen as they do in the summer. Conventional counterparts, on the other hand, cost a small fortune in planting schemes and screens designed to hide them from the rest of the garden.
Michael Littlewood, a landscape designer and advocate of holistic sustainable living, introduced the first natural swimming pool into the UK. "Put simply," he says, "it is a two-pool system, one for swimming and the other for the plants. It should be divided half and half. You either have one pool divided into two, combining a deeper swimming area and a shallower regeneration section with aquatic plants and shingle, or alternatively you could choose to have a more formal pool linked by underground pipes to the regeneration pool which is sited further away."
Despite their principles, however, some of his clients still object to the inevitable algae. "It's not harmful and it's only a problem when it's growing," says Littlewood. "You just have to be prepared to do some weeding." And if swimming in an unheated pool is a little too much on the natural side for some, then by installing solar panels and covering the swimming area at night, it can be naturally heated up to temperatures of about 28C. Another plus is that the different depths mean that the water warms up quickly and is constantly mixing with cold.
The first people to build a natural pool in the UK were Tim and Tish Rickard, who had a 2.2m-deep pool installed in their Gloucestershire garden. "It is 10m by 4m and I definitely have room to swim, not just splash about," says Tim. "In high season it is fantastic, swimming around with waterlilies. We want to keep it looking more like a wilderness, but you have to keep the plants under control - that's about the only work. There is a circulating pump, but I have never had to take it out. Of course, although it is lovely to have wildlife using the pond, with an open pool you can get rats."
Estate agents constantly remind homeowners that pools do not add value to a property, but is an eco-pool a different matter? Henry Holland-Hibbert, of the country house department of Lane Fox, suggests that it would be "a vote-winner rather than a value-winner. Indoor pools, particularly if they are in barns or such like, do add value, but a pool that is natural and beautifully landscaped would be very special. Certainly, an ordinary swimming pool that looks intrusive does put some buyers off - they look hideous and no one goes near them for eight months of the year."
The cost of a natural swimming pool is about £350 to £400 per square metre, which comes to a starting price of about £25,000 - not much different from a chlorine pool. Designing a cover and using large blocks of limestone will push up costs, according to Martin Kelly of Fairwater Ltd, a supplier. "There really isn't a huge amount of upkeep. Just some weeding and skimming the leaves from the surface - and it all dies down in the autumn."
The ideal size, according to David Everett of Anglo Aquarium Plant Company, is 200 to 300 square metres - the bigger it is, the easier it is to maintain, he points out. Fifty square meters would be more of a plunge pool. "But whatever their size they look wonderful. And I know one family who use theirs from April because the water is warmer than a swimming pool."
That happens to be just as the frog spawn appears - but this is a pool you have to learn to share.
Michael Littlewood: 01460 240168, www.ecodesignscape.co.uk;
Anglo Aquarium Plant Company: 020-8363 8548;
Fairwater Ltd: 01903 892228, www.fairwater.co.uk;
Gale and Snowden, ecological architects: 01237 474952, www.ecodesign.co.ukReuse content