If it is fish in the river, it is better to use river water directly, and tap water is needed for ornamental fish. The river itself is relatively clean, but it may be invaded by bacteria during water intake and transportation, thus affecting the health of fish. It is convenient to take tap water, but there will be residual chlorine during disinfection in waterworks, which requires some methods to remove chlorine to ensure its safety.

1. Drying: The most commonly used chlorine removal method from tap water is drying. After connecting the tap water, it usually takes one to three days to bask in the sun. In summer, the temperature is relatively high, so it takes one day to bask in the sun, two days in spring and autumn, and about three days in winter. It can accelerate the dissipation of chlorine gas by drying, and it can also raise the water temperature.

2. Aeration: Aeration is also a good method if water is urgently needed. The air head of the oxygen pump is introduced into the water, and the chlorine gas in the water can be driven out by oxygenation, thus purifying the water environment. However, the water treated by aeration should not be too much, otherwise the efficiency will be low, so it is better to use the method of drying.

3. Medication: There is a kind of drug that can remove chlorine. Pouring it directly into tap water can also remove chlorine, but the dosage should also be controlled. If it is used too much, it may cause certain phytotoxicity to fish. Usually, chlorine removers are rarely used in family fish farming, and are mostly used when aquarium shops need a lot of water.