CO2 fertilization - invented by nature
In the same way that humans and fish need oxygen to survive, plants are dependent on carbon dioxide (CO2). Plants produce their most important building material - sugar - from CO2, water and light.
A by-product of this process, which is known as photosynthesis, is the oxygen which all animals need in order to breathe. This process is the basis for all life on our planet.
Aquarium water is nearly always deficient in CO2. Natural CO2 has already been removed from the water which flows out of our taps at the waterworks, by means of aeration. The aquatic plants hungrily devour the minimal quantities which exist in the aquarium. The available supply is usually insufficient. As a result, stems and leaves appear weak and pale, with no sign of growing power. The plants’ resistance is weakened, algae settle on the leaves. In contrast to natural environments, the natural source of supply is lacking in aquaria.
In aquaria with strong growing aquatic plants, troublesome algae have practically no chance. Nutrients conducive to algae growth, such as phosphates and nitrates, are "absorbed" immediately by the plants. Plant growth starts to flag when CO2 is lacking, however.