The water change in the fish tank is usually carried out in the afternoon. Usually after 4 pm, because this time has passed the feeding period, changing water can properly stimulate the fish, promote its digestion, and also clean up the residual bait and fish manure at the bottom. At ordinary times, we should pay attention to the situation of the fish tank and see if there is much foam on the water surface. If there is much foam, we will change the water.

1. Frequency: First of all, we should pay attention to the frequency when changing water. Too often changing water will make fish have stress reaction, while not frequently changing water will lead to deterioration of water quality. Excessive ammonia nitrogen in water will also cause toxicity to fish. Therefore, it is particularly critical to control the frequency of water change, which is usually decided according to the deterioration rate of water quality, whether to change once a week or twice a week.

2. Water quantity: The water quantity of changing water is generally related to the frequency. If you change water frequently, don't change more every time. If you change water lazily, change more every time. Usually, it is enough to change once a week and one fifth at a time. If it is changed only once every two weeks, it is necessary to change one quarter or one third to improve the water body.

3. Water temperature: The temperature of the prepared new water must be close to that of the old water, which can be 1 ℃ higher, but the difference must not be too large. Too large a temperature difference can easily cause fish to get sick or even die, so pay attention to the water temperature.