Nature Aquarium CO₂ Injection

The necessity of CO₂ injection in an aquatic plant layout has become common sense. But, why is injection with a Pollen Glass the mainstream method? How do we judge if a CO₂ injection volume is adequate? Let us examine how CO₂ is injected in Nature Aquarium.

The necessity of CO₂ injection

A plant performs photosynthesis. Photosynthesis is a mechanism by which glucose, which is a substance necessary for growth, is produced from water and CO₂ (carbon dioxide and carbon dioxide gas) as raw materials using light energy. Aquatic plants in Nature Aquarium tanks photosynthesize actively and produce oxygen bubbles. A light fixture provides the light energy, and water is plentiful in the surrounding. Although CO₂ dissolves into water from the atmosphere, and fish and microorganisms generate it through respiration as well, CO₂ tends to run out in an aquarium with a lot of aquatic plants, and therefore it needs to be added artificially.

Injection method

An old method used a cylindrical vessel in an aquarium to hold and diffuse CO₂ gradually. It was like waiting for CO₂ to dissolve on its own rather than actively diffusing CO₂ in water. This method allowed only a small amount of CO₂ to diffuse in water, and therefore it could keep up with CO₂ demand only under low lighting. CO₂ in the vessel was replenished when it run out. Since it typically ran out several times a day, it was not meant for people who were not home during the day. If the vessel was enlarged, CO₂ would last longer, but the vessel became an obstruction. ADA used to sell a product called an External Diffusion Bottle (the product has been discontinued). It was an innovative product equipped with an enlarged CO₂ vessel that was placed outside of an aquarium. However, a smaller, more efficient CO₂ injection method was needed. Then a method that diffuses CO₂ bubbles continuously was developed. The white diffusion surface of a Pollen Glass has a very fine mesh. The fine CO₂ bubbles that are discharged from the surface drift slowly in an aquarium and diffuse in the water column. This method is called natural CO₂ injection. CO₂ diffuses efficiently when the CO₂ concentration in water is low. However, if the concentration is excessive, it does not diffuse easily and it is released into the atmosphere. Although CO₂ is necessary for aquatic plants, it is not useful to fish and microorganisms directly, and if the dissolved CO₂ concentration is high, fish and microorganisms are not able to breath. Although a forced CO₂ injection method has been developed, it is not practical since it has to be monitored for 24 hours a day, or a device with an accurate sensor is required to control the injection volume so as not to affect fish and other organisms adversely. (This was possible with ADA’s product IC. pH controller, which is also discontinued.) In contrast, the natural CO₂ injection by Pollen Glass is safe. Its injection volume can be easily controlled as well.

CO₂ Equipment Selection

A CO₂ bottle and a regulator are required to supply CO₂ to a Pollen Glass. An adequately large CO₂ bottle is desirable for supplying CO₂ continuously to a Pollen Glass. Since a CO₂ bottle such as Tropical Forest has a large volume of CO₂ gas that is liquefied under pressure, its internal pressure is rather high. Although a high pressure gas requires special handling, this is not a problem with a product that is designed with careful attention to product safety. The same thing is true with a CO₂ regulator that is used to control the pressure and output volume of CO₂. One must use equipment that is designed with double or triple safeguards. ADA offers such products that are designed with a great deal of attention to product safety. (Please see our catalog for more detail.) ADA offers two types of bottles: a small disposable cartridge type (Tropical Forest) and a rechargeable type (Tower/20). Customers can select one depending on the place of installation and economic considerations.

Injection Volume

Although CO₂ supply volume is controlled with a regulator, if the injection volume is large, an adequate size Pollen Glass must be selected so that the size of CO₂ bubbles is proper as well. The proper injection volume depends on the condition of an aquarium, such as the size of an aquarium, the volume of aquatic plants, and the brightness of its lighting. A Glass Counter is a good indicator for adjusting the CO₂ volume. For example, the injection volume in a 60 cm aquarium is controlled to 1 bubble per second using a Glass Counter during the initial period after set up, and the volume is increased to 2 to 3 bubbles per second when the aquatic plants grow and increase their volume. For a guideline, you can refer to the injection volume by Glass Counter that is listed in the Tank Data section of an aquatic plant layout in Aqua Journal. If the injection volume is adequate, aquatic plants give off oxygen bubbles and grow healthy. If it is insufficient, no oxygen bubbles are observed, and the new shoots will gradually wither. If the volume is too large, breathing of fish and shrimp becomes labored. Although it is desirable to decide on the proper volume by watching the condition of the living things, a Drop Checker is a good indicator for the amount of invisible dissolved CO₂. When CO₂ dissolves in water, the water turns acidic. The Drop Checker is very convenient since it indicates the excess and deficiency of CO₂ using this characteristic.

Trimming Plants and Injection Volume

The proper amount of CO₂ injection volume depends on the amount of aquatic plants. This means that the injection volume needs to be reduced when the amount of aquatic plants decreases greatly through trimming. If the condition of an aquarium becomes poor after trimming, the sudden shift in the balance of CO₂ injection volume to the plants may be one of the causes. In other words, the amount of CO₂ became excessive suddenly after trimming. Although fish and aquatic plants tolerate a somewhat excessive amount of CO₂ very well, the microorganisms in a filter and the substrate are affected easily. The injection volume should be reduced right after trimming and then be gradually increased when new shoots start to develop on plants.

Cleaning of the equipment

The equipment that are installed inside an aquarium become dirty gradually with algae and other deposits. Not only are they unsightly, but the white diffusion surface of a Pollen Glass gradually clogs, and the size of bubbles increases resulting in poor diffusion efficiency. A Pollen Glass is made of glass including the white diffusion surface. There is a number of other glassware as well. The excellent characteristic of glass is that when it becomes dirty, it can be restored to its original condition with proper cleaning, and therefore it can be used semi-permanently. Cleaning is done by simply leaving the glass in the special cleaner Superge. The ease of cleaning enables frequent cleaning and allows the glassware to retain its original beauty.

The Source of CO₂

CO₂ has been a focus of attention lately due to the global warming problem. The atmospheric CO₂ concentration is rising because of various human activities. So, where does the content of our CO₂ vessels come from? The CO₂ in the vessel is actually recycled CO₂ gas that was recovered and refined from the iron manufacturing industry, chemical industry, and boilers. Aquatic plants in an aquarium convert the injected CO₂ into oxygen. We can say that an aquatic plant layout is an environment-friendly hobby as well.