Spring is here: how to get your natural pool back on track

By |Published on: March 23, 2023|

Vegetation starts to grow again, the water gradually warms up and the days get longer. The bacteria in the filter are the first to wake up, degrading the pollutants accumulated over the winter (leaf debris, etc.) and producing the nitrates and phosphates needed by the plants. With the sunshine and these mineral salts, it's the plants' turn to get going.

Some sunny but cold days can lead to the sporadic but intense growth of filamentous algae. This is a temporary phenomenon, so leave it to nature. Simply brush the walls and vacuum up any deposits, and clean the stones later if necessary.

This is the time to check all equipment and water circulation, and to clean the pre-filters. The table below shows the maintenance schedule.

Spring (T >15°C) The plants The pool & its equipment The water
To be done at start-up Remove fallen leaves in autumn and winter. Check skimmer baskets, overflow chute and pre-filters, and clean if necessary.

Check that the overflow chamber is working properly (check that the float valve and overflow are in good condition).

Check temperature rise.

Check both water circuits, as well as the course of the stream or waterfall (water must flow freely without overflowing).

Advice Watch out for plant pests (aphids, etc.). As soon as the vegetation starts to grow again, resume regular maintenance of your bathing area (robot, brush, broom, landing net, etc.). Remove filamentous algae by hand and brush.
Just in case Replace dead or damaged plants.

Fertilize certain aquatic plants (water lilies, Thalias, Pontederia, etc.) with phosphate-free fertilizer.

Cover any exposed parts of the membrane with pebbles.

Replace skimmer shutters removed and stored over winter.

Restart the circulation pump after unblocking.
Open water tap if closed during winter.

As soon as the water has reached a temperature of 15° C, spread a bio-additive over the entire surface of your bathing area (as prescribed).


The first leaves to stretch out are those of the water lilies, often red at first, so don't be alarmed to see them trapped in the ice some days. Buds form in April*, and as soon as the frost has passed, the fragrant flowers will open continuously until autumn.

Most plants start up in April*, with acorns and reeds the fastest, along with calthas, aponogetons, euphorbias and moats.

If spring isn't too cold, the calthas bloom as early as April*, along with water clover, euphorbia and moats: your bathing area will be dressed in yellow for two to three months.

In May*, milfoil is in full bloom, thallium starts to bloom, and many flowers bloom: arrowhead, iris, lysimachia, forget-me-nots, etc., which will be joined by the flowers of purple loosestrife, pontediaria, potentilla and other plantain plants in June*: this is the most floral season of your Baignade naturelle®. (* month is a guide for temperate climates)

Animal life awakens with the sound of frogs, and you'll soon see their first egg-laying among the plants, along with the occasional newt. Aquatic insects are hatching, and notonectes and dragonflies are arriving.

Watch out for snails and slugs

Symptoms: leaves are browsed and pierced by lengthwise furrows.
Description: massive hatching in spring.
Treatment: hand harvesting or trapping.


Seasonal flora :

Juncus (rushes)

Rushes are cosmopolitan, bearing clumps of cylindrical, leafless stems with white pith. They produce greenish-brown spikes in spring, and can quickly grow to over a metre in height.

Widely used in basketry thanks to their sturdy stems, rushes are also used to make tatami mats and floor mats.



Seasonal wildlife :

Green frog (Rana esculenta)

The most common in natural swims®, it rarely exceeds 10 cm in length. It has a rounded snout and a bright green to brown back with two clearly visible lines of glands. It eats insects, worms, larvae, etc.

It reproduces very early in the spring, as soon as the water warms up, signalling the start of the bathing season: around 2,000 eggs are laid, producing tadpoles that metamorphose after 2 months.


(* indicative months for temperate climates)

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