The Eheim CO2 fertiliser unit -Eheim CO2-Set 600- simply and reliably doses the necessary amount of CO2 for an optimal and helthy plant growth in the aquarium. Aquarium water usually contains too little carbon dioxide (CO2) as it has already been extracted from the tap water at the waterworks. In addition to light, nitrogen, phosphate and trace elements, etc., the most important nutrient for aquarium plants is CO2 and, the stronger and healthier the plants, the less chance algae has to grow. Plants also produce more of the oxygen that fish need to breathe and CO2 also regulates the pH values in the water, when dosed correctly.Eheim CO2 Set 600+ CO2 reusable bottle (2000 g) with stand+ precision pressure reducer with manometers and precise dosing valve for reusable systems+ 360rotating hose connection+ CO2 specific safety hose, pressure resistant, 3m,4/6 mm+ CO2 safety diffuser including bubble counter and non-return valve for effective CO2 dosing+ water test strips for analysis o