Fish and water
Fish and waterAs the saying goes, "fish raise water first."What exactly is "good water"?With the development and research of aquaculture technology in recent years, we know that "good water" is actually a stable and balanced microbial community, which has a self-regulating function like nature, which can decompose harmful substances in the water in a timely manner, allowing fishHealthy growth and reproduction.Among the various microorganisms, the nitrifying bacteria are the most important and the most concerned. So, what exactly are nitrifying bacteria and what is their important role?Before answering this question, we must first introduce the concept of "nitrogen cycle". We know that nitrogen (N) is a very important chemical element for living things, because it can form two kinds of organic matter essential for living things: protein and nucleic acid.The nitrogen in nature is mainly in the form of nitrogen (N2) in the air. Most organisms cannot directly use it. Only some fungi, such as blue and green algae, can absorb N2 and synthesize nitrogen-based compounds.This process is called nitrogen fixation.Algae are eaten by other organisms, which are eaten up by higher-level organisms in the biological chain, and finally nitrogen compounds spread throughout the ecosystem.When these nitrogen compounds are released (biological death, or through their fallout, excreta), they are decomposed by bacteria, the main decomposition product is ammonia, ammonia is easily oxidized, some bacteria will be oxidized to nitrite, and then bySome bacteria oxidize to nitrate.Nitrate can be absorbed by plants and enter the food chain again.Nitrogen turns into organic matter and is decomposed, and then the process of forming organic matter again is the nitrogen cycle.In this way, a complete nitrogen cycle pattern is: biological (organic)-> ammonia-> nitrite-> nitrate-> biological (organic), now let s talk about what isNitrifying bacteria.The strict definition of nitrifying bacteria refers to bacteria that use ammonia or nitrite as the main source of survival energy, and use carbon dioxide (CO2) as the main carbon source.Broadly speaking, any bacteria that can oxidize ammonia nitrogen in soil or water into nitrous acid or nitrate can be called nitrifying bacteria.What needs to be clarified here is that the so-called nitrifying bacteria or nitrosating bacteria is not a certain kind of bacteria, but a general term for a variety of bacteria that can complete nitrification and nitrosation.What we usually mean by "nitrifying bacteria" refers to nitrifying bacteria and nitrifying bacteria. So why is nitrifying bacteria important?In the nitrogen cycle, when nitrogen compounds are released (biological death, or through their fallout, excreta), they are decomposed by bacteria, one of the main decomposition products is ammonia (NH3).Ammonia combines with water in water to form ammonia water (also called ammonia, its main component is ammonia monohydrate NH3 · H2O).Ammonia is a relatively toxic substance, which has a stimulating effect on fish. Ammonia poisoning can cause hemoglobin to lose its ability to bind oxygen, increase the respiration rate and heart rate, reduce the sodium content in plasma and disrupt the blood buffer system and enzyme chemistryeffect.Ammonia is converted into nitrous acid (NO2-) under the action of nitrosating bacteria or photosynthetic bacteria. This process is called nitrosation.2NH3+3O2---gt;2HNO2+2H2O+热 亚硝酸与一些金属离子结合以后可以形成亚硝酸盐，亚硝酸盐会降低动物血液的携氧能力，还会和胺类物质结合，形成具有强烈致癌The role of nitrosamines.When nitrite reaches a certain concentration, it will poison fish, shrimp, etc., or cause low resistance, causing the invasion of various pathogens. Therefore, nitrite is often compared with the infamous ammonia, and is considered to be caused by fish and shrimp.The cause of death.Fortunately, nitrous acid will continue to oxidize under the nitrification of nitrifying bacteria and be converted into nitric acid (NO3-).2HNO2 + O2 ---> 2HNO3 + Hot Nitric acid combines with metal ions in water to form nitrate.Nitrate is less toxic and is a nutrient that can be absorbed and utilized by plants, which is much less harmful by comparison.However, too high a concentration will also cause discomfort to the fish, and in a low-oxygen environment, nitrous acid will be generated again through the reduction reaction.So it is also diluted by changing the water regularly.It is because nitrifying bacteria can decompose ammonia and nitrous acid to form nitrate, which can play the role of "detoxification" in water, so its role in aquaculture and ornamental fish breeding is very important. Knowing what nitrifying bacteria are, and the role of nitrifying bacteria, lets take a look at the habits of nitrifying bacteria again.Lets take a look at the keywords of nitrifying bacteria habits: hyperoxia.Both nitrifying bacteria and nitrifying bacteria are aerobic bacteria. Sufficient oxygen is very important for the nitrogen cycle. As can be seen from the above formula, the nitrification and nitrification processes require oxygen to participate, so that nitrifying bacteria can use ammonia and nitrous acid as "food""Provide energy for it.Therefore, a certain amount of dissolved oxygen (above 2 ppm) must be maintained in the water for nitrifying bacteria to work properly.In the absence of oxygen, nitrifying bacteria will sleep or even die. Adhesion.Nitrifying bacteria are adherent bacteria.Although there are free nitrifying bacteria in the water, the nitrifying bacteria must be on the surface of the attachment to work well.In nature, nitrifying bacteria are widely distributed in soil, rocks, and gravel, and use these as attachments to carry out nitrification and nitrosation. Reproduction is slow.The growth and reproduction of nitrifying bacteria is extremely slow, it takes about 10-20 hours to reproduce one generation.Experiments show that under the natural propagation of nitrifying bacteria, the nitrification system of the newly built aquarium will take 4-5 weeks to be fully established.In food-poor and harsh environments, nitrifying bacteria can sleep for up to two years. Alkali is afraid of acid.Nitrifying bacteria prefer to grow in a neutral or weakly alkaline environment, the appropriate PH value is 6.5-8.2. Growth is inhibited in an acid environment with a pH lower than 6.
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