Moss Killer Ready to Use is an extremely fast & effective moss & algae killer for use on all hard surfaces, including walls, fences, decking, block paving, patios, drives & roofs. Its non-staining formula can also be used on terracotta (pots & statues), greenhouse & conservatory glass. Results can be seen within 3 hours. Its foamy formulation makes it easy to 'see where you've been' & is rainfast after just 1 hour. Effective moss & algae killer for use on all hard surfaces. Non staining formula. Can also be used on terracotta (pots & statues), greehouse & conservatory glass. Results can be seen in 3 hours. Foamy formulation makes it easy to 'see where you've been'. Rainfast after one hour. Contains natural fatty acids, always read the label.