Add 1 spoon per 1000 liters when algae is rampant in pond. Algae control takes 4-7 days to work. Don’t add more within the 7 day period…Algae is a air born plant  and can show up at any time. Don’t try and kill it off completely, rather control the algae. A small amount of algae on the walls of your pond is good. Algae in the water is controlled via the UV clarifier. If your water is green replace the UV tube or complete UV clarifier. See pond equipment, UV Clarifiers.