Chomp Pro Algae Mold Stain Cleaner Remover. This professional strength algae and mold stain cleaner and remover is a fast, bleach free, environmentally safe way to clean algae and mold stains from most hard, exterior surfaces. Chomp Professional Strength Concentrated Algae Mold Stain Cleaner and Remover with DST, Step 1, can be used on roofs, fences, stone, brick, pavers, concrete, decking, siding, cedar, vinyl, stucco, and patios. It will clean and remove stains caused by algae and mold and make weathered wood look like new. This product is environmentally friendly, biodegradable, bleach free and with no phosphates. A gallon makes seven gallons of cleaning solution. Depending on the stains and surface, it will clean approximately 800 square feet.