Since all planted aquariums lack CO2, it is extremely important that they are supplemented with it. In fact, 40 to 50% of a plant's dry weight is composed of carbon. For optimal condition of aquarium plants, some CO2 supplementation is necessary. The Fluval Pressurized CO2 Kits come complete with all the necessary tools needed to grow lush and vibrant aquarium plants. This disposable cartridge system is ideal for small planted aquariums (up to 115 L/30 US gal). The kit includes : High-Quality Regulator Valve Support Base High-Quality Ceramic CO2 Diffuser which produces the finest of bubbles 2-in-1 Bubble Counter & Check Valve Hose.