petnet believes that for people who keep fish, there are four types of water: one is new water, that is, tap water that has just been dried or a newly drilled well water water. Although this water is very clean, it is very different from the environment in which fish live in nature. Since there is no nitrifying bacterial community in the water, fish excrement and scattered food residues are decomposed into ammonia after spoilage, and fish are easily poisoned. The second is the old water, which is light green or light amber, rich in humus and beneficial microorganisms and algae, and has established a good ecological cycle system. After the nitrogen cycle, it is decomposed into nitrates that are harmless to fish. This water is extremely beneficial for the growth of fish. The third is green water. The organic matter content in the water is too much, so cyanobacteria, green algae and brown algae multiply, and the content of bacteria and microorganisms increases sharply. die. Fourth, back to clear water, also known as bite clear water, green water contains too much algae and microorganisms, which will deplete the oxygen in the aquarium, causing the death of algae and aerobic bacteria, making the water extremely clear, without oxygen and Standing water with a lot of anaerobic harmful bacteria.