Phosphates (PO4) are the main algae nutrients in ponds. This filter material binds phosphates and thus deprives the algae of their nutritional basis. The phosphates come from fish food, dead pond plants and dead algae. With algae treatments, the dying algae release the phosphates bound in them and nourish the next generation of algae. That’s why it’s vital to bind the phosphates!
Buy filter material or find additional information: JBL PhosEx Pond Filter .
You can find out more about algae in ponds in the Themeworld Pond: Algen .