How to remove and get rid of pool algae ?

What to do when your pool water changes color? This problem is generally caused by the appearance of algae. It's important to identify and get rid of algae quickly, as it encourages bacterial proliferation in the water and pollutes it. Find out more about the causes of algae growth, and our tips for treating and cleaning your pool according to the type of algae.

Algae may appear in the pool water.The water becomes cloudy.

Why and how do algae grow in a swimming pool?

Algae like everything in our pools: humidity, heat and light! Heavy algae growth leads to discoloration of the water and deposits on the walls and bottom of the pool. Here are the various causes of algae growth.

During the wintering period

The appearance of algae during this period is frequent, especially if you have practiced passive wintering (total cessation of filtration and treatments) or active wintering with light filtration.

Late reopening of the pool

As soon as the water temperature reaches 12°C, don't delay estimate your pool even if you won't be enjoying it for several weeks. Lack of proper treatment, combined with rising temperatures and humidity, inevitably leads to the appearance of algae.

During the summer months:

Unbalanced pH

When bathing water is insufficiently or incorrectly treated, the pH of the water becomes unbalanced and the disinfectant no longer has sufficient effect. To measure pH, use a reliable and accurate tester. When the pH is too high and the chlorine level too low, algae grow rapidly.

High temperatures

With summer heat waves, or even heat waves, water temperatures that are too high encourage the growth of algae. In fact, as soon as the water rises above 28°C, algae multiply and feed bacteria : the pool water becomes green. .

Ineffective or insufficient water filtration

Water circulation in the pool is too weak. In summer, it's necessary to adjust the filtration time to stabilize the water temperature.

Cleaning incomplete

If your pool isn't maintained regularly and rigorously, the filter and pipes can become clogged. This can contribute to the development of algae. Here are some tips to clean well your pool.

Les différents types d’algues de piscine

There are thousands of species of algae. However, you need to know how to distinguish between them in order to apply the right chemical treatment. To do this, look out for two things in particular:

  • Color of algae (green, black, yellow, etc.)
  • Its appearance (slimy, viscous, or easily detached from the pool walls)
To eradicate algae in a swimming pool, you need to know how to recognize the type of algae. Images with different types of algae: green algae, mustard algae, pink algae, white algae.


Green algae

These are the most common. Pool water turns green and stains may appear on the bottom and sides of your pool, making it slippery and slimy to the touch. Green algae can sometimes be suspended in the water.

Black algae

These appear as black, slimy stains on the walls and bottom of pools, as well as on the joints of your pool's tiles. They are particularly resistant to chemical treatments, especially chlorine. They are the most difficult to get rid of.

Mustard algae:

As their name suggests, they are yellowish in color and also settle on the bottom and sides in powder form. They are easy to remove. However, unlike other algae, they prefer shady areas to grow. The germ comes from the Sahara, clinging to dust carried by the wind. Regions with southerly winds are therefore often affected by mustard algae. They disperse into the water at the slightest movement, and are easier to spot at the start of the day.

Pink / red algae

Bright red or pink in color, these algae usually develop on plastic parts, such as skimmer baskets, liners, skimmers .... The water then turns brown.

White algae

White algae multiply mainly in shady areas of the pool. Resembling moss or absorbent cotton, it easily separates from the walls. White algae should be distinguished from algae that has died as a result of shock treatment, which can cause milky water.

How can I remove algae from my pool?

Above all, the presence of algae on your pool's lining indicates the presence of several types of bacteria. Some are dangerous to the health of swimmers! You need to intervene quickly. And remember that each type of algae requires its own specific treatment. That's why it's so important to identify them correctly, as described in the previous paragraph.

The dosages and conditions of use of the products listed below must be scrupulously respected in accordance with the manufacturers' instructions.

Treating green swimming pool water

  • Measure pH level and correct if necessary.
    • When the pH level is too low, add pH +.
    • When the pH is too high, add pH -
    • For more information, clic ici here
  • When the pH is correct, between 7.2 and 7.6 for a chlorine pool, you need to carry out a shock treatment with chlorine or use an algaecide suitable for green algae.
  • Run filtration until water is clear again
  • Using a brush, scrub the sides, bottom and waterline of your pond.
  • Use a landing net to collect as much algae as possible on the surface, to help remove it.
  • If you're not using your pool (for example, when you reopen it), cover it with a suitable cover.

Removing black algae

  • Start by brushing the walls, bottom and tile joints of your pool. It's important to get into every nook and cranny.
  • Check the pH with your usual measuring tool and correct if necessary with pH + or -.
  • Shock treatment with active oxygen
  • Add a special anti-algae product (algicide) for black algae. This product is highly concentrated: always use gloves and a protective mask.

Getting rid of mustard algae

  • Use a Stop-algues moutarde product: this algaecide is specific to this type of algae and requires a shock treatment of the water to be effective.
  • For shock treatment, use a product compatible with your usual disinfectant (chlorine, bromine, salt, etc.).
  • Filtering your pool water
  • Thoroughly clean all objects and equipment (buoys, thermometers, probes, brushes, landing nets, etc.) that have come into contact with mustard algae. Mustard algae is a germ that must be eliminated everywhere, otherwise algae will reappear, even after the shock treatment.

Eliminating white algae

  • Start by scrubbing the walls, waterline and bottom of your pond with a brush.
  • Measure pH and correct if necessary by adding pH+ or pH-.
  • Pour an anti-algae product suitable for white algae or add active oxygen for a shock treatment.
  • Use a landing net to remove as much algae as possible from the surface.
  • Filtering your pool water
  • If, after 12 hours, the water remains whitish, don't hesitate to use flocculant. Please be aware that this product is not compatible with all equipment.

How to treat red algae/pink algae

  • Red or brown water indicates a high concentration of metal ions and the presence of algae. These adhere to coatings and can create indelible stains if the water is not treated as a matter of urgency.
    • Utilisez un traitement chlore choc
    • Check water pH and rebalance as necessary
    • Add a flocculant product to maximise the chlorine shock treatment
    • Filter your pool water

How can I prevent algae in my pool?

A few daily actions can limit the development of algae.

Efficient pool analysis and treatment

Regular analysis of your pool water (pH, disinfectant and/or disinfection, water temperature) using precise, reliable measuring systems is essential to prevent the appearance of algae.

  • Maintain a normal pH of between 7 and 7.4 for a chlorine pool: basic water is a favorite playground for algae. The higher the pH (8 and above), the more likely they are to settle in your pool.
  • Check the chlorine level ((chlorine acts on water disinfection and helps prevent algae growth). If you are using stabilized chlorine, it is recommended to maintain its level between 0.7 and 1.2 ppm. If you are using non-stabilized chlorine, it is recommended to maintain a level between 0.4 and 0.7 ppm.
  • Check disinfection quality: Measuring ORP allows you to check the disinfection quality of your water. The higher the ORP concentration, the better the water's ability to eliminate dangerous micro-organisms.

Did you know there are water connected analyser such as ICO who makes automated measures of your pool water ?

Clean regularly your pool

Did you know that the weather has an impact on the quality of your pool water? During the summer, weekly maintenance of your pool helps maintain balanced, healthy water. Regularly clean the sides and bottom of your pool, as well as the filter and skimmers....

Check and adapt your filtration system

During the season, remember to clean it regularly, about once a week. In hot weather, it's advisable to turn on the filtration system at night. Here's a simple rule of thumb for calculating how long to filter your pool water: Filtration time = water temperature divided by two. For example, if your pool is at 28°C, the optimum filtration time will be 14 hours per day.

To conclude

You now have all the information you need to prevent the appearance of algae in your pool, or to know how to treat it should it reappear. If you have any doubts or questions, don't hesitate to call on a qualified professional to help you.