In nature, CO 2(carbon dioxide) is a primary nutrient for almost all plant organisms. This applies to plants that grow on land, but certainly also to aquatic plants. Under the influence of (sun) light, the plants absorb CO 2and convert it into sugars, which are necessary for growth. CO 2is therefore a very important factor in the development of pond plants.The contents of the package are sufficient to treat 4000 liters of pond water with CO 2.The CO 2 Tabs from Velda provide this necessary CO 2. Add the tablets to the water and they emit sparkling CO 2.