Co2 Carbon Dioxide in Aquarium: Why and How to use, installation of Co2 System

Co2 Carbon Dioxide in Aquarium: Why and How to use, installation of Co2 System

PrintCreate and setup an aquarium means creating a water biosystem, which is made up of plants, fishes and biological or not biological materials. To make this biosystem functional, it is crucial that the so-called “nitrogen cycle” is initiated and chlorophylline photosynthesis is therefore important the integration of CO2 (carbon dioxide) that will help the development of plants and the their reaction will provide beneficial substances to animals and the biosystem, triggering the nitrogen cycle. The main reasons why CO2 is very recommended are two:

1 – Facilitate chlorophylline photosynthesis:

6 CO2 + 6 H2O → C6H12O6 + 6 O2   As you know this is a chemical reaction that occurs with the presence of light and carbon dioxide dissolved in water or mixed in the air that reaches through the cuticle or stomachs of chloroplasts (rich in chlorophyll). The first phase of the process is called “light phase”: the energy of the light (solar or artificial by lamps) radiation is stored in some pigments. f18ee9641a3c4eb45c31dfaa0eed1f7eThe second phase, known as the “dark phase”, is biochemical: the energy stored in the first phase is made available to link water and CO2 together and form glucose with oxygen release as a product. From this, it is evident that thanks to the the presence of this gas, the plants that will grow visibly lush (at the expense of the algae) and the fishes and invertebrates that will enjoy greater oxygenation with all the biosystem will benefit healthier.

10888574735_e79132ab9f_k-1080x7052 – Avoid biogenic decalcification:

Biogenic decalcification is a natural process that make plants to take carbon when CO2 is scarce, this source they have to draw is represented by all carbonates and bicarbonates such as carbonic acid and calcium carbonate present in water. It is a highly damaging process for plants that will have to spend a lot of energy with consequent degradation, but olso for the rest of the biosystem causing a KH lowering which is a tampon factor for the PH level. With the periodic administering  of CO2 we will avoid these situations and we will stabilize PH level.

There are many ways to put CO2 in the aquarium, such as special tablets that, thanks to a chemical reaction, release carbon dioxide, or DIY methods using yeast, water, sodium bicarbonate and sugar, or (Most recommended) by means of cylinders that will hold the gas under pressure. Let’ see how to make the various installation:


(Mounting Co2 flow from the cylinder to the diffuser)

  • aquarium-co2-setup-diagramGetting a cylinder resistent to high pressures. (Commercially available disposable type, or Co2 fire extinguishers or for food use revitalized).
  • Assemble a pressure reducer at the out of the cylinder (serves to decrease the output pressure from the cylinder and there are various types, even with manometers indicating the internal preassure, to understand quantity remaining).
  • Use a rubber pipe.


  • Install a timed solenoid valve to avoid manual opening and closing (light hours open / dark hours closed).
  • Install a needle valve on the pipe outside the tank to avoid water reflux and any flooding.
  • Install on the pipe, still outside the tank, a bubble counter that will help to determine the amount of Co2 to be in the aquarium.
  • Install at the end of the pipe, in the tank, an atomizer diffuser (it has the ability, thanks to a porous stone, to divide the gas into tiny bubbles and help the better dissolution in water).
  • Install PH and Co2 analysis and detection systems in the tank.



  • sdASsadasSGet 1 bottle of 1.5 L of a carbonated drink.
  • Get 1 deflower for the drip to be used as a bubble counter.
  • Get 1 drinking straw.
  • Get 210 ml of water.
  • Get 420 gr of sugar.
  • Get 12 grams of isinglass.
  • Get 12,5 gr of beer yeast.
  • Get 1 spoon of sodium bicarbonate.
  • Boiling 210 ml of water.
  • Put the isinglass in cold water for let them softer.
  • Off the fire and put 420 grof sugar, mix until melted.
  • Add isinglass and mix .
  • When the compound is homogeneous put the contents into the 1.5L bottle.
  • Put 12,5 gr of beer yeast in a glass with hot water and mix until melted.
  • Put slowly the yeast mixture into the bottle and add 1 spoon of bicarbonate.
  • Fill the bottle with other water until aboute the end.


20101129495_tabellaIn conclusion, the presence of Co2 and an integration system in aquarium is fundamental, especially if very rich in vegetation and fishes. As we have explained, the methods are many, some cheaper like the “DIY” and some other no economical but safer and more efficient. You have to know that too much CO2 can provocate a suffering of the animals in the tank, they will become poisoned, for this reasn it will be important to keep the CO2 concentration under control by means of water drawings or with instruments that constantly detect the value (continuous test) The value it must be always less then < 30 mg/l. Regarding the amount and quantity of CO2 to be administered we can say that it is in relation to the water volume of the tank and the amount of plants, that are divided in two types: low abstorption (plants that need not much light such as anubias etc) or fast absorption (plants that need a lot of light like cabomba, upholstery plants etc). There are tables and grafics that indicate the amount to be administered based on the aquarium volume and the KH and PH values that you should know, and remember that it is advisable to turn off the diffusion during dark night hours as otherwise you will cause a CO2 intoxication to other living animales of the biosystem. Another tip, the movement of the water surface of the tank determines the loss of carbohydrate anhydride, so if you want to maintain the presence, the surface of the water must be as stationary as possible.