By Greg Morin Carbon is the backbone of all life. Every organic
molecule of every living organism is predominantly carbon based.
Given this simple fact, it becomes clear why carbon dioxide
(CO2) plays a pivotal role in the planted aquarium. Aquatic
plants extract CO2 from their environment and employ it in a
process called photosynthesis. Photosynthesis combines CO2,
water and light energy to produce simple carbohydrates and
oxygen (O2). Without additional CO2 the growth rate will be
dependent on the rate at which atmospheric CO2 equilibrates into
the water. CO2 will dissolve into CO2-free water to a degree
that is dependent on the air pressure, temperature, pH and
bicarbonate/carbonate content of the water. The final
concentration of CO2 in the water depends entirely on those
factors. Once that concentration is achieved, the level of CO2
will not change unless the plants remove it or one of the other
factors is altered. Plants remove CO2 at a rate much greater
than the rate at which it equilibrates into the