Wilko Ready To Use Green Gone 5 litre is an effective way to remove green algae, mould and lichen from all hard surfaces without having to scrub, brush or pressure wash. It's particularly effective on potentially dangerous slippery surfaces such as paths and walkways. Simply apply and leave - the results will be visible within 36 hours and it'll protect against re-growth for up to 9 months. It contains no acid or bleach and is antibacterial and biodegradable. Warning:Causes serious eye irritation. Keep out of reach of children. Always read instructions before use.