CO2 - Why ?

Magnificent plants, healthy fish - with CO2!
Why is CO2 necessary in aquaria?

Aquarium water is nearly always deficient in CO2. Natural CO2 has already been removed from the water which flows out of our taps at the waterworks, by means of aeration. The aquatic plants hungrily devour the minimal quantities which exist in the aquarium. The available supply is usually insufficient. As a result, stems and leaves appear weak and pale, with no sign of growing power. The plants’ resistance is weakened, algae settle on the leaves. In contrast to natural environments, the natural source of supply is lacking in aquaria. But who wants a centimetres-thick layer of sludge consisting of dead leaves and food residues in their aquarium?

 
CO2 fertilizsation has many other advantages
  • Part of the CO2 which dissolves in water forms carbonic acid. This means that CO2 can be used to set the pH value (acid content) of the aquarium water to ideal levels for fish and plants, similarly to those which prevail in nature.
  • Aquarium fish are particularly fond of slightly acidic water. It has a positive effect on their highly sensitive skin
  • Trace elements which are important for plants and fish are taken in more effectively
  • Unsightly lime deposits are avoided on plant leaves ("biogenic decalcification")
CO2 deficiency has serious consequences, e.g.
  • Stunted and crooked growth
  • Sudden plant death
  • Lime deposits on leaves
  • Much too high, unnatural pH values
  • resulting in stress for fish and an increased susceptibility to disease
  • Iron and trace element deficiency
  • Sudden ammonia poisoning
  • Algae infestations
 
Professional tip

Good plant growth = no algae

In aquaria with strong growing aquatic plants, troublesome algae have practically no chance. Nutrients conducive to algae growth, such as phosphates and nitrates, are "absorbed" immediately by the plants. Plant growth starts to flag when CO2 is lacking, however. Surplus nutrients are no longer consumed quickly enough. This is the chance for algae, as they need only the most minimal amounts of CO2.
That’s why a good stock of plants and regular CO2 fertilization are among the most important measures to prevent algae.

 
CO2 supply in aquaria

Various systems are available to supply an aquarium with CO2. These differ with regard to the source of CO2. Essentially, CO2 can be supplied in the form of bio-CO2 or by means of compressed gas, whereby the latter variant further breaks down into disposable and reusable systems.

Dennerle offers complete sets and accessories for all 3 systems:

 BIO-CO2 - the economical and simple means of CO2 fertilization

CO2 production on the basis of controlled and constant yeast fermentation
 

DISPOSABLE system - the practical means of CO2 fertilization

CO2 supply by means of compressed gas in a recyclable disposable cylinder
 

 REUSABLE system - the sustainable means of CO2 fertilization

 CO2 supply by means of liquefied gas in a refillable, reusable cylinder
Why CO2?
  • All plants require CO2 as a nutrient for the photosynthesis process.
  • Photosynthesis of the aquarium plants supplies vital oxygen for the fish.
  • Part of the CO2 which dissolves in water forms carbonic acid. This means that CO2 can be used to set the acid content (pH      value) of the aquarium water to ideal levels for fish and plants, similar to those which prevail in nature. Aquarium fish are fond of  slightly acidic water. It has a positive effect on their highly sensitive skin.
  • Trace elements which are important for plants and fish are taken in more effectively
  • Unsightly lime deposits are avoided on plant leaves ("biogenic decalcification")
What happens when no CO2 is supplied?

Deficiency symptoms may arise:

  • Stunted and crooked growth
  • Sudden plant death
  • Lime deposits on leaves
  • Much too high, unnatural pH values
  • This results in stress for fish and an increased susceptibility to disease
  • Iron and trace element deficiency
  • Sudden ammonia poisoning
  • Algae infestationsn
What is the right level of CO2 content?

Dennerle recommends a CO2 content in aquaria of between 15 and 30 mg/litre, with 20 to 25 mg/litre as the ideal range. The supply of CO2 which is required to achieve this level of CO2 depends on a variety of factors, such as the types of plants in the aquarium, motion of the water, surface area/volume ratio, etc. The appropriate CO2 supply level thus requires to be determined individually for the specific aquarium concerned.

How do I determine the level of CO2 in the water?

Certain correlations apply between CO2 content, carbonate hardness (KH) and pH value. The CO2 content in the water can be calculated accurately on the basis of the pH value and carbonate hardness. Suitable pH and KH tests are available from specialist retailers.

• Measure the carbonate hardness of your aquarium water.
• Read the pH value which corresponds to the desired CO2 content from the table. You should set this pH value of +/- 0.1 by adjusting the number of bubbles accordingly. Example: Carbonate hardness 4 °d, recommended pH 6.8 +/- 0.1.

How do I establish how much CO2 needs to be supplied?

Rule of thumb for basic setting of the number of bubbles: 10 bubbles per minute per 100 l of aquarium water.
Example: 200 l aquarium: 2 x 10 = 20 bubbles per minute.
Adjust the CO2 supply to the desired CO2 content in small steps. Please note: The more vigorously the surface of the water is set in motion (e.g. by filters, additional aeration), the more CO2 will be expelled from the aquarium again.

CONCENTRATION (MG/L) DEPENDS ON CARBONATE HARDNESS (°D) AND PH VALUE

Use the table as follows:

The figures highlighted in green are optimum for healthy, strong plant growth.
Measure the carbonate hardness, e.g. 5 °dH and look for a medium CO2 value (green area), e.g. 20 mg/l. Then you can read the corresponding pH of 6.9 at the top and set it as a target value with the pH controller.

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