What is low CO2

CO2: meaning, measurement & fertilization

carbon dioxide, also CO2, is next to the temperature, the pH value and the water hardness one of the most important water values in the aquarium. As part of photosynthesis, CO2 is essential for that Plant growth. In turn, high CO2 concentrations can be dangerous for fish.

In this guide you will find out everything you need to know about the CO2 content in the aquarium.

Photosynthesis and CO2

Be in photosynthesis CO2 and water converted into sugar (energy). Photosynthesis only works under the influence of light. Without photosynthesis, aquatic plants cannot survive or even grow. CO2 is that, so to speak Staple food of plants. A regular controll the CO2 content therefore makes sense.

Photosynthesis: Water + carbon dioxide + light = oxygen + glucose

Relationships: CO2, KH and pH value

The pH value is strongly related to the carbonate hardness (KH) and the CO2 content of the water. If you know 2 of the 3 values, you can calculate the missing value using the following table. In order to achieve optimal plant growth, the CO2 value should between 20 and 40 mg / l lie.

In order to achieve a high pH value, the CO2 content must be reduced and the carbonate hardness increased. For low pH values, the carbonate hardness must be reduced and the CO2 value increased. With the CO2 concentration, the pH value can only marginally controlled become. The pH value can be better adjusted via the carbonate hardness.

Measure CO2 content

Ideally, the CO2 value should be in the range 20 - 40 mg / l lie. Either is used for measurement Droplet tests or test strips, with which one can carry out an immediate measurement or permanent tests. Permanent CO2 tests determine the CO2 content using an indicator liquid that is in an urn in the aquarium. Permanent tests are more accurate and can be read daily without additional effort.

Calculate the CO2 value

If no CO2 test is available, the CO2 value can can be calculated using the table inserted above. For this, however, you need a carbonate hardness and pH value test.

Meaning of CO2

The CO2 supply to plants is comparable to the feeding of fish. Plants cannot survive without CO2. However, if the CO2 values ​​are too high, fish can be damaged. One speaks of a CO2 deficiency when there is a concentration below 15 mg / l, from an excess from approx. 50 mg / l.

CO2 shortage

  • High pH levels
  • Algae growth
  • Deficiency symptoms in plants
  • Plant death
  • poor plant growth

CO2 excess

  • Fish stress
  • in extreme cases: fish deaths

CO2 fertilization

In order to achieve optimal plant growth, the CO2 content should be around 20 - 40 mg / l. CO2 fertilization is particularly popular Aquascapes and plant tanks necessary because little or no CO2 is emitted by living beings. In community aquariums, the CO2 that is generated by the Breathing of the fish is often sufficient. Whether fertilization is necessary also depends on the individual requirements of the plants.

CO2 systems

For the CO2 fertilization one uses CO2 systems in the aquarium hobby. There are different models with a wide price range.

JBL ProFlora Bio160 bio-CO2 fertilizer system

30.01 € (May 16, 2021 10:59 pm)

OCOPRO CO2 system DLX-350 Plus aquarium with night shutdown & FULL 2kg returnable bottle

194.90 € (May 16, 2021 10:59 pm)

Sera CO2 fertilizer system for aquariums up to 300 l

205.00 € (May 16, 2021 10:59 pm)