Nitrite
Overview
Nitrite is a metabolic product, which is produced through degradation of ammonia. A too high content of nitrite is toxic for Koi. In the ideal case, the nitrite content should be at 0 mg / l. A nitrite level up to 0.3 mg / l can be tolerated for short. High nitrite pollution can be reduced with fresh air, bacteria-injection or water exchange.
Further information
Common
Metabolic end products of the Koi and decomposed organic mass (e.g. leaves) from the environment pollute the pond in form of toxic ammonia. Nitrite is an intermediate product, which is produced in the conversion of ammonia to nitrate by bacteria in the bio-filter and in the pond. This process of two-stage transformation is called nitrification (see below). The nitrite is the end product of the first stage. If the two-stage process of nitrification is disrupted, this can lead to a significant increase of nitrite.
When running in a pond filter system an increase of the nitrite concentration can be observed because the nitrifying bacteria are reproducing slowly. This can be compensated by starting injections.
Short-term increases may also be formed during a thunderstorm because the electrical discharges in the air created by the rain of nitrogen rinse into the pond.
During nitrification acid is formed. This lowers the pH value of the water. Since the buffering capacity of the water is lowered the risk of acidification of the pond increases. In the nitrification oxygen is consumed. This has an impact on the oxygen of the water.
Nitrification
Nitrification is an oxidation of ammonia (NH3) or ammonium ion (NH4 +) to nitrate
(NO3-) by bacteria. The nitrification is carried out in two steps:
In the first step, nitrite bacteria (Nitrosofizer, e.g. of the genera Nitrosamines, Nitrosospira and Nitrosococcus)
absorb ammonia. This oxidizes to nitrite ions.
In the second step, nitrate bacteria (Nitrifies, e.g. of the genera Nitrobacteria, Nitrospira or Nitrococcus)
absorb the nitrite ions, and oxidize them to nitrate ions.
Step 1: Ammonia -> bio-chemical reaction of nitrite by bacteria -> nitrite ion
Step 2: Nitrite-ion -> bio-chemical reaction by nitrate bacteria -> nitrate ions
For nitrification 4.33 g of oxygen (O2) per g of nitrate-nitrogen (NO3-N) are required.
Explanation of oxidation:
Originally, oxidation was referred to as chemical reaction of a substance with oxygen
(end product oxide). Meanwhile there is an extension of the terminology. Today oxidation
means a chemical reaction in which an oxidizing substance emits electrons to an oxidizer
(usually oxygen).
Toxicity
Nitrites are toxic. The nitrite ion reacts with the iron atoms in iron-bearing enzymes of cell respiration and haemoglobin. Since the iron conducts the oxygen-transport to the cells, this will be interrupted. At a value of 2 mg / l of the oxygen transport is completely interrupted.
Limit
A fish pond should ideally not contain nitrite the nitrite value should always be 0 mg / litre.
The nitrite content of 0.1 mg / l over a longer period of time should not be exceeded. Briefly
0.1 mg / l to 0.3 mg / l (approx. 7 days) is harmless.
With a high nitrite content of 0.2 - 0.5 mg / l it can be reduced by oxygen, bacteria-injection
and by replacing the contaminated water through fresh (emergency measure). The water levels
should be reviewed, especially following values:
pH
Oxygen content
Ammonia content
Factors influencing the nitrite content
Oxygen concentration
pH
Buffering capacity of the water
Dwell in the filter
Exposure to bio-mass
Fish stocking
Filter Characteristics
Water temperature
The warmer the water is, the better the nitrification. The optimum is at about 22 ° C are reached.
The colder the water is, the slower nitrification runs. At 12-14 degrees the process significantly
slows. Below 5 ° C the nitrification stops completely.
