Rhinox Nano CO2 Diffuser - Glass Reactor for Aquarium Live Plants Suitable for tanks below 20 US gallons, i.e. Nano tanks Atomic pores on the ceramic disc breaks down Carbon dioxide gas into tiny streams of bubbles With high surface area to volume ratio, Co2 can easily dissolve in the water Experiments show CO2 dissolve rate close to 100% Size: 1/2 inch in diameter. Note: Rubber suckers included.