Wet & Forget is EPA registered and is simple, safe and effective at removing moss, mold, mildew and algae stains from any outdoor surface. Wet & Forget is non-caustic, non-acidic and does not contain bleach. Simply dilute the concentrate and apply with a regular garden sprayer. No pre-treating, rinsing, scrubbing or power washing is needed. Each time it rains, Wet & Forget safely and gently removes surface growth. Most applications last for a year or more. It is safe to apply around plants and vegetation. Available in 1/2 gallon size. Now you will be able to eliminate those dark stains safely.