Earth Friendly Pool Builders Can Be Found on the Internet

Natural Swimming Pools Can Be Considered Earth Friendly
Natural swimming pools are quite common in Europe and can definitely be termed earth friendly because they use almost no manufactured materials or chemicals. Such a pool will cost $2000 in the United States compared to the conventional pools which can cost tens of thousands of dollars. Earth friendly pool builders have now become popular in the United States as well, as they have found that the USP of such pools being eco friendly, makes a big impact on prospective pool owners. Lists of such builders can easily be accessed over the internet, though you would need to check on the credentials of the one you choose because as yet there exists no standard certifying authority for such builders.
Image Source: Flickr : diamond_rain : https://www.flickr.com/photos/diamond_rain/4983645418/
Earth Friendly Pool Basics
An earth friendly pool will require a little larger area than conventional pools because such pools do not use any artificial walls to make the sides. They would be in earth and shaped so that the sides slope naturally and give the shape of an oversized soup bowl. You also need to keep aside substantial space for water plants which provide natural means of filtration
The filtration effect is achieved by the fibrous roots of the water plants that have bacteria that act as filters and remove any contaminants from the water. Other organisms in the plants also consume the bacteria and prevent any build up of waste. The only mechanical device that does need to be installed in such earth friendly pools is the aerator whose task it is to see that the oxygen needs of the plants are adequately met.
Sealing of earth friendly pools is easily achieved by adding bentonite to the clay or earth. Bentonite has the property of expanding rapidly and filling up any pores or crevices in an earthen embankment. This will make the pool watertight and there will be no loss of water due to seepage into the ground.
Plants need to occupy about 50 percent of the area of a pool for it to ensure that the water is always clean. These plants are best put in the shallower areas of the pool in a plant zone that contains about 6 inches of soil. Protecting this zone with a rim may be necessary to prevent the soil sliding further to the bottom of the pool. The zone will also provide a habitat for frogs and other animals that would ensure that mosquito larvae do not breed in the pool. A layer of gravel in the pool also allows a habitat for beneficial bacteria.
Access to the pool is best with a dock or structure jutting into the pool. This will ensure that the plants which are at the edges of the pool in the shallow areas will not be disturbed.
Finding the Right Builder
Once you have zeroed in on a list of earth friendly pool builders, go through the credentials of each one of them. Ask for references which you can check for yourself. Ask to visit some of the pools that they have installed and check with their owners on the service of this builder and the materials and other expertise that the builder brings to a project.
After deciding on a particular builder, go through all the specifications for the pool including all items like plants, aerators, bottom sealing methods etc. Finalize cost and time estimates and any maintenance services that you may opt for.
References
How to build a natural swimming pool - https://www.motherearthnews.com/Do-It-Yourself/2002-08-01/Natural-Swimming-Pool.aspx
Swimming pools directory - https://www.thewaterwarden.com/directory/swimming-pools.asp
Planet- Friendly Pools and Ponds - https://www.calfinder.com/blog/landscaping/planet-friendly-pools-and-ponds/