Tropica CO2 System Bio supplies aquariums up to 60 l with CO2 from a natural CO2 source for up to 60 days. CO2 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 20-25C for the best use of the product.Tropica CO2 System Bio+ for improved growth of easy and medium plants+ 60 days CO2 for a low cost+ safe to use+ easy to refill and recycle+ complete with CO2 diffuser and hose