Tropica CO2 System BioCO2 is the most important nutrient for plants. Without a CO2 supply, the plants will not thrive. CO2 System Bio is a simple solution that adds extra CO2 to the plants in the aquarium. We recommend 20 25 C for the best use of the product. For improved growth of easy and medium plants 60 days CO2 for a low cost Safe to use Easy to refill and recycle How to use the product? Pour 300 ml of hot water in the bottle. Approx. 50 C. Put on the cap (without air