In reef aquarium termilogy, carbon dosing feeds bacteria to be removed as a nutrient export mechanism.
"Carbon Fixation" is "Dynamic Equilibrium" with carbon dioxide gas in athmospher and carbon dioxide in solution that is coupled with photosynthesis to produce glucose which is a " carbon source".
http://www.fondriest.com/environment...n-chlorophyll/
What is Photosynthesis?
Photosynthesis is the process by which organisms use sunlight to produce sugars for energy. Plants, algae and cyanobacteria all conduct oxygenic photosynthesis 1,14. That means they require carbon dioxide, water, and sunlight (solar energy is collected by chlorophyll A). Plants and phytoplankton use these three ingredients to produce glucose (sugar) and oxygen. This sugar is used in the metabolic processes of the organism, and the oxygen, produced as a byproduct, is essential to nearly all other life, underwater and on land 1,24.