Mkt Chitosan Natural Clarifier for Spas & Pools 2-Pack

Chitosan Clarifier is nature's solution for crystal clear hot tubs & pools. Derived from recycled sea crustacean shells, we add plant-based enzymes. Our less water formula with 2X more active ingredients is far superior to petrochemical-based treatments. Clears cloudy pools & spas with Chitosan Added natural enzymes devour surface oils Removes impurities - improves filtration 16 oz. - Double Concentrated (use less) Product notes: Use just 1/2 oz. weekly. Equivalent coverage as 32oz. of similar products. Compare to SeaKlear brand. What in the world is Chitosan?