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When Vivien Blaj and Anthony Chung go for a refreshing dip, they share the water in their pool with tadpoles and water lilies, rushes and fish. That's because the couple opted to install a natural swimming pond on their six-acre property north of Bolton, Ont. instead of a conventional swimming pool.

"We enjoy nature," says Chung. "I don't think it would appeal to everyone, but it appeals to us." An even bigger part of the appeal is the absence of chemicals. Instead of the chlorine used in most pools, Blaj's and Chung's pond makes use of the filtering properties of plants and rocks to prevent the growth of algae.

"There's been a huge interest in swimming ponds," says Jason Jayne of Tumber & Associates Landscape Consultants in Orangeville, Ont. "If we had to pick out a few trends, it's in the top three of the last five years for sure."

Indeed, the concept is huge in Europe, where natural swimming ponds now outnumber conventional pools. An estimated 50,000 ponds have been constructed in Germany, Austria and Switzerland in the past 20 years.

The landscaper who built Blaj's and Chung's swimming pond, Simon Ackles-Dold of Genus Loci Ecological Landscapes in Schomberg, Ont., explains that it contains a plant filter zone and a plant-free swimming zone separated by a submerged retaining wall. Water quality is maintained through a combination of bio-filters, UV filters, mechanical aeration and the filtering plants.

In addition to being environmentally responsible, swimming ponds are beautiful to look at. The ponds are lined with thick sheets of black PVC plastic and surrounded by gravel-bottomed shallow areas planted with such typical water plants as cattails, bulrushes, sedges, duckweed and water lilies. Water is continuously pumped through the plant zone, keeping it pure and oxygenated. The banks of the ponds are lined with granite rocks and planted with wetland plants that further filter any groundwater flowing into the pond.

"We provide proper equipment to Mother Nature and then she takes over," explains David Antcliffe of Toronto's Ponds in the City. "Think of a swimming pond like a natural lake. It's a natural ecosystem and that's the key."

Says Chung: "One of the things that we wanted to accomplish with the landscaping and the natural pool itself was to try and restore some of the ecosystem that had been lost around the house when it was built."

One downside is that swimming ponds take up more space than conventional pools. The pond's plant filters and tiered design (shallow ledges around the swimming area are needed for the aquatic plants) require a larger property to build on.

"For every foot down, you're putting in a shelf," explains Antcliffe. "So, if you want to go six feet deep in the middle section, let's say, you're going to have to have a 50-by-50-foot pond to have any kind of area to swim in."

Another issue is cost. Large swimming ponds can run to hundreds of thousands of dollars, but Genus Loci's Jean-Marc Daigle says that a modest pond like one that his firm installed in Loretto, Ont., which had a 16-by-30-foot swim zone, would cost between $40,000 and $50,000, including aquatic plantings, a dock, a waterfall and a pump system.

And, as Antcliffe points out, natural swimming ponds cannot be heated. But like the tadpoles and other wildlife that they share their pond with, Blaj and Chung don't mind the inconvenience. In fact, a pond made the most sense to the couple because of Canada's short summer season.

"We don't have to empty it, so we can actually use it as a skating rink in the winter," Chung says.

And here's another upside: "Even if you don't swim in it during the summer, you still have all the benefits of having a pond near you."


Pond essentials

The four elements necessary for creating a balanced ecosystem in a pond include:

Aquatic plants that filter toxins and absorb the nutrients that can feed algae. The plants also provide oxygen and create shade to help keep the water cool.

Rocks, gravel and large stones to provide surfaces for the growth of beneficial bacteria, which consume algae-producing nutrients and contaminants.

A waterfall that allows water turnover and ensures oxygenation. Adequate oxygen levels are needed for supporting pond life and preventing stagnation.

Aquatic creatures such as fish and frogs to keep the pond clean by eating nutrients and contaminants.


Experts across Canada

André Boisvert of Le Courtil in Mont-Saint-Hilaire, Que. (514-942-5561)

Jason Jayne of Tumber & Associates Landscape Consultants in Orangeville, Ont. (519-941-3867, Simon Ackles-Dold of Genus Loci Ecological Landscapes in Schomberg, Ont. (1-877-467-2079, David Antcliffe of Ponds in the City in Toronto (416-489-8166) Jeff Cutler of space2place design in Vancouver (604-646-4110,