How often goldfish change water generally depends on their own situation. If the water is turbid or the goldfish lacks oxygen, it should be changed immediately. Usually, it is changed once every three or four days in summer, once a week in spring and autumn, and once every half month in winter. One third of the original water body is changed at a time.

For fish farmers, there are four kinds of water:

First, fresh water, that is, tap water that has just been aired or well water that has been newly drilled. Although this kind of water is very clean, it is quite different from the environment in which fish live in nature. Because there is no nitrifying bacteria community in the water, fish's excrement and scattered food residues are decomposed into ammonia after spoilage, and fish are easily poisoned.

Second, the old water, which is light green or amber, is rich in humus and beneficial microorganisms and algae, and has established a good ecological circulation system. After nitrogen circulation, it is decomposed into nitrate that is harmless to fish. This kind of water is extremely beneficial to the growth of fish.

The third is green water. There is too much organic matter in the water, so cyanobacteria, green algae and brown algae multiply in large numbers, and the content of bacteria and microorganisms increases sharply. The water is thick green, and sometimes it stinks, which can easily cause the whole tank of fish to die.

The fourth is to return to clean water, which is also called biting clean water. It is because there are too many algae and microorganisms in green water, which consumes the oxygen in the aquarium, causing the death of algae and aerobic bacteria, and turning the water into stagnant water with no oxygen and a lot of anaerobic harmful bacteria.

From this, we can know that not all water is suitable for goldfish's life, and the most suitable water for goldfish's growth is old water. The so-called water cultivation is the process of changing new water into old water.

At present, most of the water we use to raise fish is tap water, so the first step to raise water is to remove the toxic substance-chlorine from tap water. The method of chlorine removal is relatively simple. After the water is filled, let it stand for 2-3 days, or dry it 1 day (if it is urgently needed, add 0 100 kg of water. 63 grams of baking soda, namely sodium thioate, can be used immediately).

After the fresh water is dried, it should be put into the tank and filtered, so that the pump can turn the still water into flowing water, and then put the fish into the tank. "Breaking into the tank" means putting several cheap, strong and easy-to-raise fish into a new tank. After a few days, the excrement of the fish will decompose into ammonia in the water, which is the same as that of tap water with ammonia. Too much ammonia will kill the fish, so the most important thing in raising water is to remove ammonia from the water. Usually we use nitrifying bacteria to remove ammonia from water. Nitrifying bacteria can be added to the water, but they need attachments to survive in the water. If there is no suitable attachment, adding more nitrifying bacteria will not work. They will die in the water, and nitrifying bacteria usually attach to filter cotton or bottom sand. In fact, the flowing water will naturally produce nitrifying bacteria in a few days, which is also the most commonly used method for cultivating nitrifying bacteria. The cultivation of nitrifying bacteria is the second step of water cultivation.

Here is a brief introduction to the subtle chemical changes of nitrogen cycle and how nitrifying bacteria work.

After the fish enter the tank, they will discharge ammonia and other wastes into the water, and the ammonia concentration in the water will increase, and the nitrifying bacteria in the living water can decompose ammonia (note: it takes a week or more for nitrifying bacteria to form, so during this time, the fish will be seriously injured). When nitrifying bacteria community forms, the ammonia concentration will decrease until it reaches zero.

However, things are not so simple, because nitrifying bacteria can only convert ammonia into nitrite, but it is also toxic to fish! Therefore, we should understand that the concentration of nitrite is increasing while the concentration of ammonia is decreasing. So don't think that you can sit back and relax after the ecology is established. If you want to reduce nitrite, you should change water regularly and quantitatively to lower its concentration, so as to maintain a relatively stable ecology and keep the water in the old water state.

We should also tell you that old water is what we pursue, and green water also has many benefits for goldfish. For example, green water can make goldfish darker, but there are too many algae in this water to see fish, which is not suitable for viewing. Moreover, when there are too many algae, the fish will lack oxygen, so we should pay attention to controlling the algae content in the water when raising goldfish with green water.