Why Co2?

Planted aquariums are all about balance. Balancing nutrients, amount and quality of light, plant loads, the substrate or soil you use, the fish you decide to introduce.

C6H12O6 + 6O2 → 6CO2 + 6H2O + 32 ATP (energy)

Respiration is the process in which plants ‘breathe’ or respirate, and allows for plants to use this stored energy from photosynthesis and break it down into usable energy. And much like humans, plants respire 24 hours a day in normal conditions through their ‘lungs’ or stomata. Aquarium plants aren’t any different. Photosynthesis occurs in the leaves and stems only, while the whole plant respires. While photosynthesis absorbs UV for energy, respiration is just a set of metabolic reactions needed to break down nutria.

Planted aquariums are special in this factor. They aren’t in constant need of excess CO2 thanks to the anaerobic and aerobic processes of bacteria and microfauna living in the pores of the soil. Naturally, there are fish, inverts, turtles, decaying matter being washed into the environment to provide these healthy levels of CO2. It's a cycle that can only be partially replicated.

Many aquarium hobbyists find themselves buying CO2 injectors to maintain healthy levels of growth. A planted aquarium will store and gradually release CO2. Let my clarify though. CO2 will almost always be your limiting factor. You can have an intense light, great pump and filter, ideal substrate, but more often that naught, the CO2 will be the limiting factor.The illustration below highlights how the barrel won’t hold anymore water because of the lack of a certain minerals and nutrients available in the substrate. Very often, the short stave in the limiting factors of aquariums, is the dissolved levels of CO2 in the water. The law of minimum states that  growth is dictated not by total resources available, but by the scarcest resource!

Air pumps and water pumps are also necessary to regulate healthy dissolved oxygen in the water, but this is easier to manage.

Maintaining the balance of all of these factors is essential to maintaining steady and healthy growth. The key point of respiration is to actually use the energy and oxygen created by photosynthesis. This is also why it is essential to simulate night and day. It is similar to depriving a human of sleep and can severely stunt growth or worse.