Nutri-Defense works by binding up excess nutrients, feeding Pond-Clear bacteria and polishing pond water. After Nutri-Defense has bound up the excess nutrients, the flocculated nutrients sink to the bottom, out of the water column. It is at this stage that our Pond-Clear natural bacteria can work at it's highest efficiency, breaking down nutrients on the bottom. Nutri-Defense allows you to "manage the nutrients" so you can manage water clarity.