Everything You Need to Know About Natural Swimming Pools

What Is a Natural Swimming Pool?

Thinking about installing a natural pool? Unlike conventional chemical pools, natural swimming pools operate on the same principles as lakes and streams. Water movement and the harmonious interaction of beneficial microbes and (sometimes) plants create a healthy environment for swimming, not to mention an exquisite space in your own backyard!

Natural swimming pools can be built in all shapes and sizes and are appropriate for all U.S. climates. A natural swimming pool can be an aquatic oasis populated with lilies and reeds, or rectilinear concrete with an infinity edge and nary a plant in sight. A conventional pool can even be converted into a natural swimming pool!

Homeowners consider a natural swimming pool for any number of reasons:

• Disliking the harsh chemicals of a convention pool
• Adding natural beauty to their landscape
• Expansive design options — from a multilevel meandering wildlife sanctuary to a minimalist lap pool
• Desire to welcome more wildlife into the yard
• Living in a dry climate or under water restrictions (no water changes)
• Interest in sustainability and reducing environmental impact

How Natural Swimming Pools Work

In a natural swimming pool, the water is cleaned by moving it through a biological filter, the same tried-and-true system that results in clean water in lakes and streams around the world!

Dirt and debris, algae and heavy metals — what conventional pools label contaminants or pollutants — in a natural pool system are considered nutrients for the biological filter to consume.

Natural swimming pools vary in design, but all include these elements:

• A closed-loop system, meaning you’re not adding anything to the mix
• A biological filter made of millions of microorganisms and sometimes plant life
• A dedicated swimming zone separate from the filter
• A plumbing system that circulates water between the filter and swimming area.

Building a Natural Swimming Pool

Installing a natural swimming pool is similar to a conventional pool, from permitting to finding professionals to handle the design and construction. National companies will offer guidance and oversight to projects in areas that don’t have a lot of homegrown expertise. There are also DIY natural swimming pool plans and kits available online. To hear experts tell it, it is next to impossible for a pool company without experience in natural swimming pools — much less the average homeowner — to get it right, so you should look to people with this specialized knowledge.

Natural Swimming Pool Construction

A natural swimming pool can be rectilinear or freeform and is constructed of typical pool materials. The important part is that the interior is nonporous to maintain that closed system. The plumbing system for a natural swimming pool is not unlike a conventional pool’s. A pump uses pipes to circulate the water, and skimmers manage debris. You may be digging for a single basin or two, depending on the filter.

Natural Swimming Pool Additions

Natural swimming pools can have water features, heaters, lights, vacuums and covers. There is one conventional pool add-on you won’t find in a natural swimming pool: a device that disinfects the water like an ionizer or ozone generator. The premise of a natural swimming pool system is that it’s purified naturally, by pushing water through that biological filter.

Placement and Size of the Natural Swimming Pool

Local codes, sun and wind exposure and water management on the property will help determine the best place to put your natural swimming pool. Avoid low areas prone to flooding or where runoff from other parts of the property would enter the pool.

Fundamentally, a natural swimming pool is all about the biological filter. The size of it will be based on an expected nutrient load determined by the pool surface area and the number of users. A regeneration zone could require as much as 1/3 of the overall space you have allocated for the pool. Plant-free pools require less filter space and there is no minimum size.

Biological Filter Selection In Natural Swimming Pools

There are now two types of biological filters in use for a natural swimming pool system. The site limitations and your aesthetics are the two main factors that will influence which filter you use. Some pools incorporate both filters.

The Regeneration Zone Filter

What it is: The regeneration zone is the original biological filter. Is a shallow area populated with aquatic plants that gives a natural swimming pool that iconic aquatic garden appearance. In early designs, the regeneration zone always surrounded or abutted the swimming zone, but newer designs site it separately. This allows for the appearance of a conventional swimming pool and a prosaic garden pond elsewhere in the yard for filtering.

How it works: This type of filter contains a diversity of plants for a variety of tasks. They work in concert with a biofilm of microorganisms living around their roots to filter nutrients from the pool and oxygenate the water. Like any home garden, the climate zone, footprint, sun exposure and the other garden inhabitants will inform the selection of plants. Aquatic plants that are native to the region should be used, and plant density is important. Plants from a few categories are needed:

• Emergent plants and marginal plants share space at the edge of the regeneration zone. They want their roots to stay submerged, but the rest of the plant stands above the water. They filter the water of nutrients, serve as a windbreak, prevent soil from entering the system and provide a habitat for wildlife. Examples: cattails, reeds, rushes, grasses like sweet flag and bloomers like pickerelweed.
• Submerged plants stay under water. They are the powerhouse oxygenators of the pool. Examples: deep water–rooted plants such as common waterweed and other pondweeds, marshweeds and swampweeds and submerged plants that float near the surface like coontail and hornwort.
• Floating plants don’t make contact with the pool bottom. They lower the temperature in the pool by providing shade and offer shelter for important microinhabitants of the pool. Examples: large-leafed charmers like water lilies, lotus, water hyacinth and Frog’s bit, as well as small constituents like watershield (an aquatic herb) and fairymoss (an aquatic fern).

The Biofilm Filter

What it is: The newest natural swimming pool systems rely entirely on a biological filter comprising microorganisms, sometimes called a biofilm filter or just a biofilter, and don’t use plants at all. This filter allows for a smaller overall footprint and expands the contemporary style possibilities for a natural swimming pool. It also lowers the build cost.

How it works: A biofilm is basically a commune of different microbes that live happily together doing tasks that benefit one other in that I’ll-grab-dinner-if-you-cook-it kind of way. The biofilm filter was developed on the realization that the vast majority of filtration in a regeneration zone goes on in these microscopic communities living around the plants anyway, not within the plants. And this filter is still based on a natural ecosystem, but instead of a lake or a pond, it’s a river or stream! For this reason, a biofilm filter is a fast-flow filter, and the pump moves water in these natural swimming pools more quickly than pools with regeneration zones.

Benefits: Plant-free systems have advantages over a natural swimming pool with a regeneration zone. One obvious advantage is the diminished footprint. For example, BioNova’s biofilm filter exists separately in a pit small enough to be hidden under a deck. This opportunity provides an aesthetic benefit for homeowners who aren’t digging the lagoon vibe and would rather a modern look for the pool. A plant-free pool should also be less expensive to install because of the lack of a regeneration zone. Some of the conventional pool features that are hard (or impossible) to incorporate into a pool with a regeneration zone abutting it — diving boards, automatic pool covers, pool alarms — are no issue.

Maintaining a Natural Swimming Pool

Like any pool, a natural swimming pool requires maintenance. The design and type of pool will dictate tasks. You can expect more maintenance during the first couple of years while you’re establishing a happy ecosystem in your microenvironment. Regular upkeep for a natural swimming pool looks a lot like a conventional pool:

• Skimming and vacuuming
• Maintaining plumbing, electrical and solar components
• Testing water quality
• Adding water to compensate for evaporation

At the end of the day, a regeneration zone is a garden, so pruning plants and controlling overgrowth are part of the deal. Winterization in cold climates might involve cutting back the plants and netting. After winter or weather events, you’ll replace some plants. Biofilm filters require backwashing.

The Cost of a Natural Swimming Pool

Adding a natural swimming pool starts at $60,000 and can be many times that. The design opportunities run from free DIY plans to thousands of dollars for professional drawings. Permitting, materials and labor costs vary by locale and scope of the project. Natural pool designer Total Habitat reports a typical cost between $70,000 and $150,000. BioNova’s model with a regeneration zone is usually $100,000 and up. Its version with a biofilm filter averages $60,000 to $75,000 for a 16x32 pool.

Annual operation and upkeep costs are frequently far less with a natural swimming pool than a conventional pool. There are no water changes or expensive chemicals to add in a natural swimming pool. Because the biological filter acts as a heat sink, it can be less expensive to heat and temperatures are more stable.

The Pros and Cons of Natural Swimming Pools

Natural swimming pools offer benefits over a conventional pool:

• Cheaper to operate
• Lack of harsh chemicals
• Expansive design possibilities, everything from a minimalist rectilinear pool to a multilevel aquatic oasis
• Friendlier to the environment by not sucking up resources or adding chemicals to local ecosystems. Regeneration zones provide welcoming habitats for local wildlife, including threatened species.
• Year-round enjoyment! The swim season can be longer thanks to the biological filter. Regeneration zones are still lovely aquatic gardens when it’s too cool to swim. Freezing winters are icing on the cake with a natural pool. (Seriously, you may have a backyard ice rink for part of the year!)

There are a few downsides to a natural swimming pool over a traditional pool. Cons include:

• It can be a challenge to find a knowledgeable contractor in smaller US markets.
• It can initially take more time to get the balance right.
• Natural swimming pools with regeneration zones are frequently more expensive to install and require more space and maintenance because of the aquatic garden.

Natural Swimming Pools FAQ

What is the difference between a natural swimming pool and a swimming pond?

They're different terms for the same thing. In Europe, they're typically called natural swimming ponds. In the U.S. they're typically called natural swimming pools. Designers, installers and dealers use additional terms — recreational ponds, living pools, bio pools — to delineate a pool model that has aquatic plants from one that doesn’t. They all amount to the same thing: natural fun!

If I call it a pond instead of pool, does that exempt me from local building codes governing pool safety?

That’s a hard no. If it’s intended for swimming, it doesn’t matter what you call it: Follow all your local construction requirements to make the space safe and secure. Natural swimming pools are designed, built and permitted through the same process as conventional pools — they’re just chemical-free.

Is a natural swimming pool cheaper than a traditional pool?

Generally, no. For professional installations, a natural swimming pool with a biofilter is comparable in price to a conventional pool. A natural swimming pool with a regeneration zone is usually more expensive than a conventional pool because of the extra space needed for your plant component.

Is a natural swimming pool cheaper to operate than a conventional pool?

Yes. Operation and upkeep costs are often less because of the contained design of a natural swimming pool (no water changes) and its self-sustaining nature (no chemical additions).

Is a natural swimming pool easier to maintain than a conventional pool?

Depends. A natural swimming pool will require some upkeep, and the nature and extent will be determined by your type of pool and inclusions. You’re not adding chemicals or changing the water like a conventional pool, but you may be weeding and planting.

Can I use ozone or UV to treat my natural swimming pool?

According to guidelines of industry bodies and best practice, a natural swimming pool should rely exclusively on biological filters and water movement to clean the pool. That said, you will find contractors in the US that incorporate supplemental devices like UV sanitizers into bespoke systems.

Is a saltwater pool a type of natural swimming pool?

Not at all. In a saltwater system, you are still chlorinating the water: You’re just using sodium to generate chlorine instead of adding it directly to the water. Chlorination is like pool chemotherapy by indiscriminately killing all the microbes in the pool. A natural swimming pool uses good microbes in balance.

Are there bacteria in a natural swimming pool?

Yes, but it’s a myth that clean means the absence of bacteria. In a natural swimming pool filter, there are all types of beneficial microbes working together to create a clean swimming environment, one that is free of pathogenic bacteria, viruses and other harmful microbes. Natural swimming pools use the same indicator organisms (e.g., E. coli) that you test for in a conventional pool, and natural pools frequently outperform conventional pools!

Is swimming with bacteria kind of gross?

Nope, the bacteria in the biological filter are the good guys, like the ones living on your body. You’re also not swimming in the filter. That’s where the design of the natural pool system comes in. Water clarity in the swimming zone is one indication that your system is operating smoothly.

Will a natural swimming pool attract mosquitoes?

It isn’t supposed to! The water in a natural swimming pool is always on the move, making it inhospitable to mosquito larvae. In fact, the presence of mosquitoes could indicate a problem in the plumbing.

Will frogs, turtles and other wildlife move into my natural swimming pool?

Like any pool, wildlife will surely visit; but whether they move in or not will depend on your natural swimming pool type and arrangement. If you have a regeneration zone, that’s likely why you picked the design! Soon enough, the tiny U-Hauls will show up.

Can I deliberately put wildlife in my natural swimming pool?

Depends on who you ask. Fish, amphibians and reptiles add another variable to water quality control. Some natural pool professionals encourage it, and some discourage it, so make sure you discuss your desires with the contractor at the beginning of the project.

Can my dog swim in my natural swimming pool?

Yes, in fact, pets are an important part of the design process! The pool contractor should ask about who will be using the pool to determine the biological filter size. So, pets, children, the standoffish neighbor who loves you after spotting the pool contractor’s sign in the yard — all are important.

Are there plants to avoid using in my regeneration zone?

Yes! Invasive and non-native species are a no-no. Native plants that are hard to control should be avoided. Natural pool contractors know what should thrive in your environment. Another valuable information resource is your university extension office.

Is my climate a good one for a natural swimming pool?

If you have a local swimming season, sure. Natural swimming pools are modeled on the ecosystems of nearby bodies of water. If any climate is a challenge, it’s the intensely hot, humid one but there are natural swimming pool installations across the Southeast and Southwest US.

Can I use a pool heater in a natural swimming pool?

Yes! Just don’t subject the pool to sudden temperature changes and use local bodies of water as a temperature guide. BioNova permits artificial heating up to 86 degrees in its installations but if local temperatures exceed that naturally, it’s okay. Electric, gas or solar pool heaters are all fine.

Can I install water features in a natural swimming pool?

Definitely. It is common to incorporate a waterfall or spillover to move water between a regeneration zone and the swimming area. Fountains can lower the temperature and help oxygenate the water. A vanishing edge is an excellent skimmer. You can have all the things.

How much space do I need for a natural swimming pool?

Cocktail pool or Olympic-size lapper, make your natural swimming pool whatever and budget will accommodate. There’s a natural swimming pool design for any environment.

Does my natural swimming pool have to look like a pond or lagoon?

Not at all. You can have a sleek rectilinear natural swimming pool and an idyllic water garden across the yard. Or opt for the natural swimming pool with a biofilm filter. Your guests will be surprised to learn the pool is natural.

What if I want my natural pool to look like a pond but I don’t have space for a large regeneration zone?

BioNova’s hybrid pool designs use a biofilm filter for the filtration work and incorporate plants for ambiance. Total Habitat uses the pool walls for a biofilm filter, requiring a smaller regeneration zone footprint.

Can I turn my conventional pool into a natural swimming pool?

Sure! In fact, some of your existing pool equipment like pumps and filters might be incorporated into the conversion. You’ll lose space to accommodate the filter or need to provide space nearby, and the pool vessel surfaces may need to be waterproofed. The easiest pool conversion is usually a plant-free biofilm filter.

Can I turn my existing pond into a natural swimming pool?

In some cases. Small ponds or those that see water runoff are not appropriate for a natural swimming pool conversion. The easiest and least expensive conversion may be one in which you turn your pond into a regeneration zone for a similarly sized swimming pool you construct nearby.

I’m ready to learn more: Where do I start?

• Visit long-established companies BioNova and Total Habitat to learn about their designs and get connected with local talent.
• If you’re DIY-minded, Total Habitat has a Natural Pool Academy with an eBook, lessons and plans.
• See where the natural swimming pool got started at Biotop.
• Learn about the common essentials for natural swimming pools followed by members of The Association for Swimming Ponds and Natural Swimming Pools.