Removing green algae with washing powder: does it really work?
Washing powder is sometimes used against green algae, but is that a good idea? Read what does and does not work.

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Green algae on your deck, garden furniture or fence is a common problem, especially in damp seasons. Many people try to remove it with washing powder, but is this the best solution? Although washing powder can loosen dirt, it has drawbacks for both the environment and effectiveness. In this article, we discuss the pros and cons of washing powder and show you how to remove green algae effectively and in an environmentally friendly way with Osmo Terrasreiniger.
Drawbacks of washing powder
Although washing powder is sometimes recommended, it has major drawbacks:
- Not intended as a green algae cleaner: the effect is short-lived and superficial.
- Not environmentally friendly: chemicals can harm soil life and surrounding plants.
- Bad for drainage: washing powder residue can prevent water from draining properly from the deck.
- Risk of stains: it can leave a white haze on wood and tiles.
Do you want to clean your wood properly and keep it free of green algae for longer? Then Osmo Terrasreiniger is a much better choice.
Benefits of Osmo Terrasreiniger
Osmo Terrasreiniger offers many advantages over washing powder:
- Specially developed for wood: cleans your wooden deck thoroughly without damaging the surface.
- Effective removal of green algae: penetrates deeper than surface cleaning products.
- Economical: 1 liter of cleaner is enough to clean 30 to 100 m² thoroughly.
- Environmentally conscious: you dilute the cleaner with water and only use what you need.
- Easy to use: works with a stiff brush or coarse broom for thorough cleaning.
Video: Removing green algae with washing powder
In this video you will see how to remove green algae from wood.

Groene aanslag verwijderen: hoe verwijder ik groene aanslag?
Step-by-step plan: removing green algae with Osmo Terrasreiniger
For a thoroughly clean surface without damage, Osmo Terrasreiniger is a much better alternative to washing powder. Follow these steps for an effective result:
Dilute the Osmo Terrasreiniger
Fill a bucket with lukewarm water and add Osmo Terrasreiniger. The right ratio is:
- 1:25 for light soiling
- 1:1 for stubborn soiling

Apply the cleaner
Pour the mixture evenly over the surface or use an empty garden sprayer to spray the cleaner. Make sure all green spots are thoroughly wet.

Let the product work
Let Osmo Terrasreiniger soak in for 10 to 15 minutes. This loosens the green algae and deposits, making them easier to remove.

Scrub the surface
Use a stiff brush or a stiff broom to scrub the deposits loose. Work in the direction of the wood grain.

Rinse with clean water
Use plenty of water to rinse away the loosened deposits. Make sure the water drains away and no residue is left behind.

Let it dry thoroughly
Let the deck dry. When the sun is shining, it dries faster and the deck stays free of green algae for longer.

Follow-up treatment: protect your wood
Follow-up treatment: protect your wood
Do you want to keep your deck clean for longer? Apply a protective finish after cleaning:
For wooden fences: Osmo UV-Beschermingsolie
For wooden decks: Osmo Terras-Olie
For vertical and horizontal wooden parts such as garden furniture: Osmo Natuurlijke Olie-Beits
For stone patios and tiles: Osmo Steen en Terracotta Olie
These products help protect your deck or tiles against moisture and dirt, making them easier to keep clean.
Tips to keep green algae away for longer
- Make sure your deck has a slight slope so that rainwater does not collect.
- Adding gravel or plants around your deck reduces moss growth.
- Plants do not like excess moisture, so make sure there is good drainage.
Supplies
In addition to these products, you will also need a bucket of water or a garden hose.
Maintenance advice
- Clean at least twice a year, especially in autumn and early spring.
- Always use an environmentally responsible cleaner such as Osmo Terrasreiniger instead of harsh products.
- Make sure water drains away properly so that no damp spots remain where green algae can form. In autumn, you will notice that this is how green algae develops.
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