Wet and Forget 5 Litre Mould, Lichen and Algae Remover, Non-caustic, Non-acidic. Mould Lichen & Algae Remover 5 Litre cleans anything with no effort. Non-caustic, Non-acidic, Contains no bleach! (No shelf life), Biodegradable PH8 (Water PH7) Just mix 1 part Wet & Forget with 5 parts water in a garden sprayer.
eBay