1. The reasons for the high nitrite in the aquaculture water.
The whole nitrogen conversion process:
The conversion from nitrogenous organic matter to ammonia nitrogen takes a short time and is handled by a variety of microorganisms.
From ammonia nitrogen to nitrite is served by nitrosifying bacteria, which grow and multiply at a rate of 18 minutes, so their transformation time is not long.
From nitrite to nitrate is served by nitrifying bacteria, the growth rate of nitrifying bacteria is relatively slow, and its reproduction rate is 18 hours per era, so the conversion time from nitrite to nitrate is much longer.
When the concentration of ammonia nitrogen reaches its peak (3 4 days), nitrous nitrogen begins to rise.
When the concentration of nitrous nitrogen reaches its peak (3 4 days), nitrate nitrogen begins to rise. The effective decomposition of nitrous nitrogen takes 12 days or more.
In the aquaculture water body, due to the large amount of feeding, resulting in a large amount of nitrogen accumulation. Nitrogen is converted into ammonia nitrogen, nitrite and nitrate through the action of various microorganisms, which are absorbed by algae and aquatic plants on the one hand, and nitrate is converted into nitrogen gas by denitrification when conditions are ripe.
If a certain state of self-equilibrium is reached in the water body, and there is no external interference (such as no disinfectant), then the nitrogen cycle of the water will be relatively normal, and the tri-state nitrogen will always be maintained in a stable state.
However, in the aquaculture water, due to the regular use of disinfectants, the harmful and beneficial bacteria are all killed, the lack of oxygen often causes the nitrification process to be blocked, which is the main reason for the high content of ammonia nitrogen and nitrite in the water, due to the rapid conversion of ammonia nitrogen, so the problem of nitrite acid is the most prominent.
Of course, temperature also has a great influence on the nitrification of water, and when the temperature is low, the nitrification of nitrifying bacteria is weakened, resulting in nitrite accumulation.
Second, the harm of nitrite is too high.
Nitrite is highly toxic to fish and shrimp, and the mechanism of action is mainly through the respiration of fish and shrimp from the gill filaments into the blood, which can oxidize normal hemoglobin into **hemoglobin, so that the protein that transports oxygen promotes the function of oxygen. Tissue hypoxia leads to hypoxia of fish and shrimp, and even suffocation and death.
Many ponds have anorexia of fish and shrimp, and high nitrite is one of the main reasons. In general, when the concentration of nitrite in the water body reaches 01 milligram liter, it will be harmful to farmed organisms.
Symptoms after nitrite poisoning: anorexia; Swims slowly and reacts unresponsively when touched; rapid breathing, often breathing on the surface; The body color becomes darker, and the gill filaments are dark red.
3. Treatment methods when nitrite exceeds the standard.
Necessary conditions for nitrite degradation:
First of all, there must be algae absorption, to prevent nitrite ** - water to fertilizer;
second, nitrifying bacteria can be transformed into --- frequent use of biological agents;
Third, there should be sufficient oxygen to cooperate in decomposing organic matter, so as to avoid affecting the reproduction of nitrifying bacteria--- usually open more aerators, and sprinkle oxygenators in bad weather.
First aid measures: sprinkling salt can degrade the toxicity of nitrite.
Studies have shown that chloride ions (Cl-) can degrade nitrite toxicity. This is due to the fact that both nitrite ions (NO2-) and chloride ions (CL-) need to pass through chlorine cells on the gill plates to enter the fish, and NO2- increases the difficulty of entering the fish body due to the competition of Cl- in the chlorine cell suction site, thus reducing nitrite toxicity.
When the nitrite of the water body exceeds the standard, the appropriate amount of calcium chloride, magnesium chloride, salt and other chlorides can be splashed to increase the concentration of chloride ions, under normal circumstances, when the chloride concentration of the water body is 6 times the concentration of nitrite, it can inhibit the toxicity of nitrite to the breeding organisms.
At present, the practical and effective methods are: in the morning, you can use coarse salt or sea crystal to splash the whole pool to detoxify (5 kg per mu and rice), and detoxify with antidote or water purification products in the afternoon; And mix salt in the feed to detoxify.
Start the aerator or sprinkle the whole pool with chemical aerators.
Start the aerator or splash the whole pool with chemical aerator to make the pool water have sufficient dissolved oxygen, so as to enhance the conversion of nitrite to nitrate, so as to reduce the nitrite content in the water body.
Ammonia ion chelators, activated carbon, adsorbents, humic acid polymers are used.
Ammonia ion chelators, activated carbons, adsorbents, humic acid polymers and other water quality adsorbents such as substrate cleaners or prebiotic ammonyl are used to adsorb or degrade nitrite through ion exchange.
Decomposed by microorganisms.
By decomposing nitrite by microorganisms, microbial preparations such as bacillus, photosynthetic bacteria, nitrifying bacteria, actinomycetes, etc. can be used.
Fertilizer water. When the water is fertilized, the algae will grow more vigorously, which can not only keep sufficient dissolved oxygen in the water, but also promote the conversion of substances and energy in the water body, which can provide favorable conditions for the conversion of nitrite.
Increasing the amount of VC in feed also plays a role.
Nitrite is oxidized to nitrate with a strong oxidizing agent.
Such as potassium bisulfate complex salt.