Why Marine Aquarists Need Carbon Dioxide

The end product of photosynthesis, many corals and algae require carbon dioxide for their success in the form of hydrogen carbonate...

Carbon dioxide, with the completion of the third grade, you should have learned that it is the end product of the process known as photosynthesis.

Symbiotic, or light relying corals, Tridacna Clams, Anemones and algae require light to enable them to feed, grow and survive. Hence, photosynthesis is evident in all marine reef aquariums housing zooxanthellae, and with this comes carbon dioxide.

Often, a sense of panic enters the minds of aquarists when the word carbon dioxide and reef aquarium is mentioned simultaneously in the same sentence. Poor information, lack of knowledge regarding carbon dioxide and its importance and the urban legend that carbon dioxide promotes macroalgae and other potential nuisances, are often to blame for this.

The later statement holds true only during the initial set up and maturation of an aquarium. For the avid, conscientious marine aquarist maintaining a reef biotope, carbon dioxide is necessary to the success of their reef aquarium for a few reasons

Let's get back to the idea that carbon dioxide in excess will cause an outbreak of nuisance algae. As a tank begins its maturation process, the water goes through all sorts of changes as the cycling process is carried out. Ammonia, nitrite and nitrate levels begin to spike at various stages of the cycling process as the various beneficial bacteria form and increase to counter act with the excess nutrients in the aquarium water.

As this infancy stage of an aquarium's life unfolds, an excess of carbon dioxide will result as bacteria and microorganisms begin to populate an aquarium. Water changes will help to replenish depleted oxygen in aquarium water and reduce carbon dioxide levels as well as the suitable amount of living organisms that will take a strong foothold within your tank.

As carbon dioxide increases the pH of the aquarium's water will fall making the water more acidic, whereas, as carbon dioxide becomes depleted, pH levels will rise causing an alkaline water reading. Carbonate hardness and pH have a strong tie with each other.

Since this is true and we now know that pH is effected by the amount of carbon dioxide in tank water, these three variables should be measured and thought of as one in the same, ultimately due to their close bond with each other. Testing kits that say they test for carbon dioxide in aquarium water, in my opinion, are a waste of money. They are basically glorified pH testing kits since the close knit ties between pH and carbon dioxide. By testing your pH level, you are ultimately determining carbon dioxide levels indirectly.

Remember a high pH means carbon dioxide levels are low and vice versa.

Carbon dioxide reacts with saltwater creating carbonic and hydrogen carbonate ions making saltwater more acidic. Many aquarists use this dilemma to their benefit when incorporating Kalkwasser into their aquarium to raise calcium and alkalinity(buffering capacity).

The pH of kalkwasser is roughly 12 so by introducing the kalkwasser when carbon dioxide levels are the highest and pH drops you are able to raise the calcium level while negating the excessively high pH make-up provide by the kalkwasser. Basically the employment of carbon dioxide is a way, essentially, of stabilizing the pH of marine water and aids in the maintenance of the overall wellbeing of an aquarium as well.

Since, knowing that similarities and close bonds between carbon dioxide, carbonate hardness and pH do in fact exist, we now can act and use this info to our advantage by creating a stable and properly managed aquarium water to ensure our corals, clams, anemones and other invertebrates and living organisms receive a steady dose of carbon dioxide and oxygen needed to grow and feed as well as the wellness of an aquarium as a whole with be up to snuff!