Green algae remover (Groene aanslag reiniger)

Yes, this is not a cosmetic product for humans, but it is still a useful one for keeping your garden tiles clean. It is also an extremely simple formulation that anyone can prepare.

Many commercial products use either benzalkonium chloride (BAC) or didecyldimethylammonium chloride (DDAC). Both substances are quaternary ammonium compounds that effectively kill algae and moss by disrupting cell membranes, causing leakage of cellular contents. BAC may be slightly less potent than DDAC, but it is cheaper and easier to source.

The typical working concentration of BAC in green algae removers is approximately 0.5%. This means the supplied material should be diluted 100 times (BAC is commonly supplied as a 50% aqueous solution). To prepare a 0.5% solution, mix 50 mL of the 50% BAC solution with water and dilute to a total volume of 5 L. For heavily affected areas, a concentration of up to 1% can be used.

Method of use: spray the diluted BAC solution onto a dry surface affected by green algae and leave it for 1–3 days. Rain should be avoided during this period, as it may wash the product away. Once most or all of the algae has disappeared, it is advisable to reapply the solution to help prevent regrowth and ensure longer-lasting effectiveness.

When preparing the solution, add the BAC to water and mix gently to avoid excessive foaming. The solution should not be allowed to enter ponds, as even diluted BAC is toxic to fish and other aquatic organisms. Pets should also be kept away from the treated area until the surface is completely dry.

Why make it yourself? Because it costs only a few cents instead of several euros for a product that is approximately 99.5% water.