How Often Should You Change the Water for Home Aquarium Fish? A Detailed Guide to Water Change Precautions

Many people nowadays keep fish at home; on one hand it helps relieve stress, and on the other hand it carries the meaning of bringing in wealth. So how often should you generally change the water for fish kept at home? What precautions should you take when changing water? Let's take a look below.

1. How often should you change the water for home aquarium fish?

Generally speaking, when the weather is relatively cold in winter, the water in the tank will not need to be changed so quickly, so it does not need to be changed as often as in summer. When we notice the fish starting to float to the surface and gulping air, it means the water in the fish tank is already lacking oxygen, and that is when we need to change the water. We can also grow some beneficial aquatic plants in the fish tank; they can supplement oxygen to the water through photosynthesis. In addition, when replacing with new water, pay attention to the temperature difference of the water; the temperature difference must not be too great, otherwise the fish will be very uncomfortable and become ill.

2. Which kind of water should be used for water changes?

1. Raw water: Raw water refers to tap water or well water that has just been drawn and has not been treated by standing in the sun; its water temperature often differs considerably from the water temperature in the fish pond, and it contains a lot of chlorine. This kind of water is extremely harmful to fish.

2. New water: New water is tap water, well water or spring water that has been left to stand and settle for about 2 to 3 days, and is clean water equal or similar in temperature to the fish pond water.

3. Old water: Old water is the dirty water at the bottom of the fish pond that contains feces and filth, including the rearing water in the pond that has not been changed for a long time.

4. Green water: Old water in which more green algae float contains plenty of green algae, which are also very good supplementary feed for fish. This kind of water has less decomposed organic matter and more dissolved oxygen. Fish are often raised in tender-green and clean old water; the fish raised this way have the strongest appetite, are robust in body, bright in color, and develop very quickly.

5. Reverted clear water: If you find that the old green water in the pond has suddenly turned into clear water, with much of the green algae settled at the bottom of the tank, this phenomenon is called reverted clear water. This kind of water easily causes fish disease and needs to be completely replaced.

3. Common water change methods

1. General water change: Under normal circumstances, especially in hot summer, as long as you persist every day in gently siphoning out 1/10 to 1/5 of the feces and dirt at the bottom of the fish pond (tank) together with the old water using a rubber hose, removing dust on the water surface and floating feces, and then slowly adding new water of the same temperature along the wall of the pond (tank), the water quality can be kept clean. This water change method is unlikely to injure the fish, is simple and safe, and is most suitable for home fish tanks or those keeping fish in small ponds.

2. Partial water change: Partial water changes are mainly carried out in two situations.

① In hot summer and early autumn, when the rearing water in the fish pond (tank) has been changed only a few days ago but the water color turns green extremely quickly (because the amount of feed given is on the low side), and the water quality is still clean, in order to prevent the fish from scalding their tails, you can scoop all the fish out of the pond (tank), then make the water in the pond (tank) rotate in a spiral, wait for a moment until it is still, siphon off 1/3 to 1/2 of the dirt and old water from the center of the pond (tank) with a rubber hose, then add the same amount of new water at the same temperature, and then scoop the fish back into the original pond (tank) to keep them.

② When the water in the pond (tank) has been changed only a few days ago and the water color is still good, but floating heads appear because too much food was fed that day, emergency measures must be taken. The method of changing the water is the same as described above. If it is a large fish pond at a fish farm, there is no need to scoop the goldfish out; instead, use a folding blocking net to enclose the fish on one side, then use a scoop net to gently rotate the water in the pond for several dozen seconds, wait for the water to become still for a moment, and then open the drainage gate to slowly drain the water, or use a suction tube to remove the excess fish food, feces and old water from the center of the pond (tank), or use a fish scoop net to remove the excess fish food from the center, then drain off 1/4—1/2 of the old water, and finally add the same amount of new water at the same temperature. This method is commonly used as an emergency measure at fish farms or in homes when too much food has been fed.

3. Complete water change: A complete water change is often a water change method carried out together with turning over the pond (tank) and selecting young or adult fish. It is usually adopted only when the water quality has seriously deteriorated, the moss has grown too long, or the fish are too densely stocked.

① When there is no spare pond available, you have no choice but to scoop all the fish into a basin, or put a net cage into the water of an adjacent pond for temporary keeping, and add an oxygenating head inside the basin or net cage to increase oxygen. Then scrub off the moss on the walls of the original pond, rinse thoroughly and clean, refill with new water at the same temperature, let it stand for a moment until the water temperatures are equal, and then scoop the fish back into the original pond (tank).

② If there is a spare pond and new water available, then you only need to scoop all the fish into a basin or net cage, select and handle them separately; those that need to be divided into separate ponds go into separate ponds, and those that do not need to be divided can be moved into the new water once the water temperatures are equal. With this water change method, special attention should be paid to water temperature, and it is best to carry it out before 9 a.m. on a clear day. However, this method is generally only suitable for adult fish or larger young fish, and should not be used for fry. If conditions permit, before a complete water change, you can first fill a spare pond (tank) with aged water, and then scoop the fish directly into the spare pond (tank); this is better. In this way the water temperature changes little, the fish are more likely to adapt to the new environment, and the fish are spared the suffering of being squeezed together in the basin or net cage. This water change method is generally carried out about once every half month in spring and autumn. In the hottest summer weather, when the water temperature reaches above 28°C, the water color easily becomes very dark and the water quality easily becomes turbid, so a complete water change should generally be carried out once every 5—7 days. In winter, when the water temperature drops to around 4°C, the fish move slowly and their appetite decreases, and the water quality is not easily spoiled, so unless there are special circumstances, the water is generally not changed completely.