Naturalized pools are generating increasing interest among those seeking a more natural, chemical-free, and environmentally friendly bathing experience. In contrast to traditional systems based on chlorine, salt, ionization, or UV and ozone treatments, ecological pools offer an alternative based on biology and the physical processes that occur naturally in lakes and rivers.
Currently, this type of water treatment system is experiencing considerable expansion, especially among those seeking to combine sustainability, landscape integration, and well-being. Below, we explain in depth how these systems work, their components, advantages, disadvantages, maintenance, and key technical aspects to understand why they are becoming increasingly popular.
What is a naturalized pool?
A naturalized swimming pool , also called a biopool or ecological pool, is a facility designed to facilitate bathing in an environment where water purification occurs entirely naturally . This means not using chlorine, salt, ionizers, UV rays, or any chemical or physical system that eliminates the aquatic biodiversity inherent in a healthy ecosystem.
Its operation is inspired by the natural water cycle and is based on an artificially created ecosystem, in which water is filtered and purified through gravel, aquatic plants, and microorganisms . The goal is to maintain optimal water quality, ensuring it is clear and free of pathogens without chemical intervention.
The fundamental design of these pools consists of two distinct areas:
- Bathing area: Main space dedicated to swimming and enjoyment, with variable depths depending on use.
- Regeneration or purification zone: Annexed area, which may be physically connected or separated, where aquatic plants, filter substrate and, occasionally, small benign fauna such as fish and amphibians are housed.
These two areas are connected to allow the constant circulation of water, which guarantees natural purification through biological and physical processes.
How does purification work in naturalized pools?
The purification system in naturalized swimming pools mimics the natural purification processes found in rivers, lakes, and wetlands. In these systems, water circulates between the swimming area and the regeneration zone using a low-consumption pump or, in specially designed pools, thanks to the natural slope of the land. Let's look at each component in detail:
Structure of the regeneration zone
The regeneration zone is the heart of the purification system and is composed of several layers of filter materials:
- coarse gravel: Provides a stable base that promotes drainage and the settlement of beneficial bacteria.
- Fine gravel: Allows safe rooting of aquatic plants and improves fine particle retention.
- Arena: Optionally, a layer of fine sand is added on top, optimizing mechanical filtration.
- Specialized substrateIn advanced projects, a mineral or clay substrate enriched with nutrients suitable for aquatic plants is used.
Aquatic plants and microorganisms
In this area, ornamental and purifying aquatic plants play an essential role. Some of the most common species are:
- Water lilies (Nymphaea spp.)
- Reeds and cattails (Typha spp. and Juncus spp.)
- Aeneas (Schoenoplectus)
- Water hyacinth (Eichhornia crassipes)
- Floating and submerged plants such as Myriophyllum, Ceratophyllum and potamogeton.
The selection of species depends on the climate, surface area, depth, and landscape design. The roots of these plants host colonies of beneficial microorganisms (biofilm) that help decompose organic matter and remove pollutants such as nitrites, ammonia, and phosphates.
Mechanical and biological filtration
The purification process in naturalized pools includes two major systems:
- Mechanical filtration: Gravel and sand retain solid particles, leaves, insects, dust and impurities that reach the water.
- Biological filtration: Bacteria and microorganisms in the substrate and roots transform nitrogen and organic compounds into harmless nutrients that are absorbed by the plants.
Oxygenation and water circulation
The plants themselves, through photosynthesis, release oxygen into the water , which is essential to promote the presence of aerobic microorganisms and prevent the development of pathogenic bacteria that thrive in oxygen-poor environments.
The circulation system can be passive, using differences in height, or assisted by a low-consumption pump, ensuring that the total volume of water passes through the purification zone several times a day . In this way, the water in the pool is always in optimal condition in terms of clarity and cleanliness.
Types and levels of technology
Naturalized pools come in a wide variety of designs depending on their level of technology:
- Swimming pools without technology: Water movement depends on wind, gravity, and soil conditions, without the use of pumps or electricity. These are less common and work best in climates and water with low organic loads.
- Swimming pools with basic technology: They use a low-consumption pump, skimmers and sometimes drive systems to ensure adequate water flow between both areas.
- Advanced naturalized pools: They integrate extra filtration systems (phosphate reactor, cyclone filters, sieve filters, etc.), especially in areas with water with high levels of nutrients or in public or intensive use pools.
The choice between one system and the other depends on the initial water quality, the local climate , the expected use, and the balance between sustainability and maintenance needs.
Why is purification important in natural pools?
In every swimming pool, the water is exposed to contaminants: leaves, insects, dust, skin debris, oils, and sunscreens. These materials decompose, generating ammonia, nitrites, and phosphorus —compounds that fuel algae growth.
The eutrophication process (excessive accumulation of nutrients) can lead to the proliferation of algae and bacteria, causing turbidity, unpleasant odors, and health risks. The natural purification system limits these phenomena to:
- Reduce organic matter and nutrients, preventing massive algae growth.
- Promote biological balance which minimizes the presence of pathogens that are dangerous to health (such as Escherichia coli, Pseudomonas and Legionella).
- Prevent the formation of toxic byproducts generated by traditional chemical disinfectants.
Advantages of naturalized pools over other systems
- No harsh chemicals: The water is suitable even for people with sensitive skin or allergies.
- Reduction of energy consumptionFiltration and pump systems are usually energy-efficient, taking advantage of natural dynamics whenever possible.
- Saving water: It's not necessary to empty the pool periodically. Only the evaporated water is replenished.
- Biodiversity promotion: A habitat is created for plants, benign insects, birds, and small amphibians, improving environmental quality and promoting sustainability.
- Landscape and aesthetic integration: The design can be adapted to any environment, from urban gardens to rural spaces, enhancing the visual value of the garden.
- More natural and healthier bathing experience: The water has a unique texture, temperature and smell, without the side effects of chemicals (itching, odor, eye and skin irritation, etc.).
Maintenance and care of the purification area
Maintenance of naturalized swimming pools differs from that of conventional pools, but it's not necessarily more demanding if the design and planting have been done properly. The main care requirements are:
- Regular pruning and trimming of plants in order to prevent excessive growth and maintain the balance between species.
- Replacement or replanting if any plant dies or becomes sick.
- surface cleaning Weekly: Removal of leaves, insects and debris with a net or pool cleaner.
- Cleaning the substrateAvoid excessive sediment buildup that could reduce filtration efficiency; add gravel or substrate as needed.
- Nutrient and pH control: Periodic water analysis to adjust plant quantity, species type, or water flow if necessary.
- Maintenance of the pump and drive systems to ensure optimal circulation and oxygenation.
Depending on the season, maintenance may be more or less intensive. For example, in late autumn, it's a good idea to remove leaves and clean the bottom to avoid excess humus. Winter requires minimal maintenance, while in summer, cleaning should be more frequent.
Common problems and solutions in the purification of naturalized pools
- Excessive algae growth: This is usually due to excess nutrients or an imbalance between plants and microorganisms. Solution: Add more treatment plants, increase water flow, manually remove algae, and check the efficiency of the biofilter.
- Turbidity or bad smell: Indicates an unbalanced ecosystem or excess organic load. Solution: Review the number of plants, remove debris, and, if necessary, increase oxygenation and filtration area.
- Pollution by organic waste: Accumulation of leaves, twigs, pollen, or food scraps (if fish or wildlife are present). Solution: Maintain regular cleaning and use nets or bottom vacuums.
- Presence of insects and mosquitoesMoving water and the presence of benign fauna (tadpoles, dragonflies, fish) usually prevent the proliferation of mosquitoes, but if they do appear, use natural traps or adjust the water flow.
- Blocked filters or pump: This can be caused by excess solids. Solution: Preventative cleaning and periodic inspection of the suction and return elements.
Technical aspects and recommendations
- Dimension of the filtration areaOn average, it is recommended that the regeneration zone occupy between 30% and 60% of the total surface area, depending on the design and use.
- Quantity and type of plants: It is usually recommended between 3 and 5 plants per square meter to achieve optimal efficiency.
- Temperature control: They can be air-conditioned, although the shallow areas of regeneration help to make the water warmer naturally.
- Consumption and savingsEnergy consumption is significantly lower than that of a conventional pool; no water changes are required except for evaporation.
- Aesthetic integration: Choose species that adapt to the climate, are native or low-maintenance, and add landscape value.
Naturalized swimming pools in Spain and current trends
Interest in naturalized swimming pools is growing in Spain. Regions like Catalonia, Andalusia, and Madrid already have numerous private and public facilities, and more and more professionals are training in biological purification techniques and aquatic landscaping.
Legislation and regulations are advancing to facilitate the implementation of these solutions in private and community settings, and designs are evolving to integrate new technologies that optimize water use and energy savings.
Choosing a naturalized swimming pool means opting for an ecological, healthy, low-impact solution that offers long-term savings and unique landscape and recreational value . By maintaining a balance between the plants, the filter substrate, and proper water circulation , it's possible to enjoy a safe and pleasant swim in harmony with nature and without the drawbacks of traditional chemicals.