For aquarium plants, the correct CO2 level in the water is of great importance. Carbon dioxide serves as the main nutrient for the plants and thus promotes growth to its full potential. Plants use CO2 for photosynthesis, providing the water with vital oxygen. They help prevent algae growth, remove pollutants, offer hiding spots, and reduce pathogens. This practical CO2 direct diffuser eliminates the need for a reactor in the aquarium, a bubble counter, and a check valve, and thanks to its ingenious operation, it also saves 20% of CO2. The only requirement is the use of an external filter with a suitable hose connection. The direct diffuser should be integrated into the hose as close to the external filter as possible to maximize the distance the CO2 travels in the hose. A vertical installation position allows for the best readability of the bubble counter.