Co2 Products - Carbon Dioxide is the most important requirement for plants besides Light and Water. Still, knowing this, a surprising number of hobbyists still do not use it in their aquariums. Not many things differentiate the expertise level of a hobbyist like the use or non- use of CO2 in a freshwater planted aquarium. Step up to expert results with this simple devise. Homegrown DIY CO2 systems are great for the tinker'er, but very few get the results that a store bought quality system can achieve.