Ultra Hull Cleaner removes safely and effectively algae, fatty and oily residues, stains, rust stains, scum, zebra mussels and limpets boat hulls. Although ULTRA GREEN HULL CLEANER is a powerful cleaner, the product is gentle on the boat surfaces such as: anodized aluminum, finished gel, wood, metal and fiberglass. Powerful cleaner removes most difficult stains. The thickened formula ensures that the product sticks to the surface to be cleaned in order to avoid waste. Safe for the user. Noncorrosive. Acid-free formula Biodegradable. Low aquatic toxicity. phosphate. Pleasant odor. Easy to rinse.