The three myths to dispel about natural pools

By | November 20, 2022
natural pool water

Before building a natural pool, many people ask me some classic questions, which I want to answer in this article in order to clarify to everyone these possible doubts.

The first myth that needs to be dispelled is “in a natural pool the water turns green”.

Green water is due to single-celled algae, which can occur in a pond where there is a very high organic load, which is normally due to the presence of lots of fish, or even worse due to the presence of turtles, ducks or geese. Other factors that generate this high organic load are residues of fish food and an abundance of rotten leaves that can be deposited on the bottom.

As you may have already guessed, green water can occur where there are a lot of fouling animals, and obviously no fish or other aquatic animals are contempled in a natural pool!

A co-factor that favours the presence of single-celled algae (in addition to fouling aquatic animals) is the presence of large temperature changes and direct sun exposure of the water surface.

This means, for example, that green water is mainly generated in a pond with many fish, which also has the entire surface free, i.e. no aquatic plants in it.

In a pond, as in a natural pool, many aquatic plants must be planted so that they cover a certain area of the pond or of the natural pool.

The percentage of surface coverage with aquatic plants will clearly be higher in a fish pond than in a natural pool.

Aquatic plants do an excellent job of phyto-purification, so organic substances and pollutants that could turn the water green (ammonium) are transformed by the phyto-purification process into nitrites and then nitrates. The nitrates in turn are taken up by aquatic plants as a source of nutrients.

This is why, thanks to aquatic plants, a pond or a natural pool becomes a true ecosystem where the water remains naturally clean.

Of course, you need to find the right aquatic plants for your natural pool based on your specific context. It is not enough to just put plants in at random and hope that everything works. I have examined this topic in the article “How to choose aquatic plants for a natural pool“.

Moreover, in this series of 4 free videos about aquatic plants you can find out which are the 3 types of essential plants for a well-balanced pond and how to cultivate them.

The second myth to dispel is ‘a natural pool attracts mosquitoes”.

Mosquitoes are attracted to puddles of stagnant water where they can lay their eggs. You have probably left some containers in your garden which filled up with a bit of water in the rain, and then after a few weeks you notice that they were full of insects up to 1 cm long, wriggling around like worms… mosquito larvae! This is the ideal environment for mosquitoes to breed.

In a pond, acquatic plants attract insects that are antagonistic to mosquitoes, such as water striders and dragonflies. For this reason, for example, in our nursery, where we have 14 ponds with a surface area of between 300 and 500 m² each for the cultivation of aquatic plants, plus another 2 lakes dedicated to wild flora of around 1500 m² each, you will never find mosquito larvae.

The only short period when you might find mosquito larvae is the initial 1-2 months when you have just built a new pond and there are not yet enough aquatic plants to attract the antagonistic insects, but as soon as they arrive, you will never see mosquito larvae in the water again.

In a natural pool we also have water movement due to the continuous recirculation between the swimming pool and the plant pool. If the antagonistic insects already keep mosquitoes and mosquito larvae away, the slightly rippling water will also prevent mosquitoes from laying their eggs, as this is not their preferred environment.

The third myth to dispel is “natural pools only work in cool places”.

This doubt is linked to the fact that in hot places more algae or green water may form (but as explained in the first point, temperature changes and exposure of the surface to the sun, and not the heat itself, are a co-factor that favours green algae, in addition to the excess of organic substances in the water).

First of all, I would like to point out that I have a lot of clients in very hot places, such as Sicily, where in 2021 a heat peak of 48 degrees was reached, and there are no significant differences in ponds and natural pools.

The plants to be planted should obviously be chosen according to the climatic characteristics, i.e. the plants that we use in a natural pool located in a cooler climate area and those located in a warmer climate area are largely different, as they should be.

The basic thing is that you have to design a well-balanced system with a certain surface area dedicated to bathing and a certain surface area dedicated to aquatic plants.

There are also a couple of things to bear in mind if you want to set up a natural pool in a very hot location.

The first is that if there is a larger volume of water, it will stay clearer generally. So the larger the volume of water, the greater the stability of the ecosystem, the better the water quality.

So to put this into practical terms, for example, a 1.50 m deep pool is better than a 1.30 m deep one. Also, for example, if the substrate for the marsh plants is 60 cm deep, it is better than 40 cm (even between gravel or lapillus there is always a certain volume of water).

The second expedient is to include a UV lamp among the technical equipment of a natural pool, suitably sized according to the climatic characteristics of the location. These lamps are designed to damage the single-celled algae that cause green water and any malignant bacteria that might come into a natural pool.

These lamps are already integrated in some filter models, but you can decide whether to activate them or not.

For example, in our natural pool, which is located in Piedmont, Northern Italy, these single-celled algae have never formed and therefore we do not need to activate these UV lamps.

If you have a natural pool, especially in a very hot location, it is therefore important to plan and size them correctly, then you can easily decide if and when to activate them!