The frequency of changing water for goldfish mainly depends on the size of the fish tank, the season, and the density of the goldfish.
Small - sized fish tank (5 - 10 liters): It is recommended to change the water daily or every other day. Each time, replace one - third to one - half of the water volume to keep the water quality fresh.
Medium - sized fish tank (20 - 50 liters): Change the water every 3 - 5 days, replacing 20% - 30% of the water volume each time. If the fish tank has a filtration system, the water can be changed every 2 - 3 days.
Large - sized fish tank (over 50 liters): Change the water once a week, replacing 20% - 25% of the water volume each time.
Seasonal adjustments: In summer, due to the relatively high water temperature, goldfish have a strong metabolism and excrete more waste. It is advisable to increase the frequency of water change. In winter, the frequency of water change can be appropriately reduced.
Precautions when changing water:
Water temperature difference: The temperature of the new water should be close to that of the water in the fish tank. Generally, the temperature difference should be controlled within 1℃ to avoid subjecting the goldfish to a temperature shock.
Chlorine removal: Tap water contains chlorine, which can harm the gills of goldfish. It is recommended to let the tap water stand for 24 hours or use a professional chlorine - removing agent.
Gradual replacement: Avoid changing all the water in the tank at once. Replacing one - fourth to one - third of the water volume each time is relatively safe. This can improve the water quality without disrupting the ecosystem in the fish tank.
By following a reasonable water - changing frequency and paying attention to these precautions, the health of the goldfish and the cleanliness of the water in the fish tank can be ensured.