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How to Change Fish Tank Water

To better take care of the fish in your aquarium, you should regularly change the water in it. It can help remove the toxins in the aquarium, control the level of pH, ammonia, nitrates and so on. But how to change fish tank water? Is it difficult? What should we prepare before changing water? This article will tell you the answers.


Benefits of water changing

1. Remove waste

There is much waste in our fish tank. In addition to the waste our fish produce from excrement and respiration everyday, the uneaten food or plants and fish which have died also contribute to the production of waste.

These waste products will accumulate in our fish tank and contaminate the water. If we ignore the waste, our fish tank will become dirty day by day, which will influence the health and growth of our fish. Water changing can help with removing the waste that filters can not remove in your fish tank.


2. Reduce toxic substances

In addition to the waste, some toxic substances in the fish tank will poison your fish.

Water changing is the cheapest and fastest way to reduce toxic substances. You don’t have to buy other equipment or wait for it to take effect. The only thing you need to do is to change some water in your tank.


3. Offer trace elements and essential minerals

Fish need trace elements and essential minerals to grow. The trace elements and essential minerals will reduce with time passing by, so you need to replenish them. Water changing will be a good choice.


Tools of water changing

  • Some buckets: used for containing the clean water and your fish
  • Fishnet: transfer your fish from the tank to the bucket
  • Algae cleaner: remove the algae on the tank
  • Gravel vacuum: siphon water and clean substrate
  • Water conditioner: condition clean water
  • A thermometer: test the water temperature
  • Water test kit: test the water parameters
  • Clean hands: use the above tools


Steps of water changing

Step 1 Get your equipment ready

We have mentioned the tools needed for water changing. But do remember, even the new tools are not clean, there may be invisible bacteria on them. So before you change your water, make sure your tools have been disinfected.


Step 2 Get your clean water ready

Fill your bucket with water from a faucet or other clean resources. Put the water conditioner in the bucket and then use the water test kit to test the water parameters. Repeat these steps until the water is suitable for fish to live.


Step 3 Settle your fish

Before you change the water, you need to settle your fish. You can put them in a bucket or any other clean container, but do remember to put some water from your fish tank into the container because fish are very sensitive to water. Use a fish net to transfer your fish in case of hurting them.


Step 4 Unplug the electrical equipment

Many filters and heaters can not do well without being submerged in water, so it is a good idea to unplug the electrical equipment in your aquarium.


Step 5 Clean the fish tank

  • First, you need to use an algae cleaner to clean the glass of your fish tank.
  • Secondly, you have to clean the filter and other equipment because there is much waste accumulating.
  • Thirdly, remove or clean the dirty plants and decorations.
  • Finally, if you set a substrate in your aquarium, you should use a gravel vacuum to clean the substrate.


Step 6 Remove partial dirty water

After cleaning the fish tank, you can start to remove the dirty water from your fish tank with a siphon or other tools. It’s not wise to pour all of the water because there are so many beneficial bacteria in it, which is helpful for fish to grow. In general, removing about 10%-15% of dirty water is enough, but if your tank is large or you have not changed the water for a long time, you can remove more.


Step 7 Add the clean water

Use a thermometer to make sure the clean water is about the same temperature as the water in your tank. If you are satisfied with the parameters of the clean water, you can now add it to your tank. Also, you can set up your cleaned equipment.


Step 8 Set up and plug the cleaned equipment

Once you have added the clean water to your fish tank, the next step you need to do is to set up the cleaned equipment and plug it to let it work.


Step 9 Put your fish back

Everything is ready, you can now put your fish back into your clean fish tank!


Step 10 Clean your tools and store them

Disinfect your tools after using them and store them in a clean place for your next use.



  • Do not forget to condition the new water before you add it to your tank.
  • Check the parameters of water before you add it to the tank, especially the pH level.
  • Check the temperature of the old and new water.
  • Do not use tools that have not been disinfected.
  • Do not pour dirty water unless you have unplugged the electrical equipment.
  • Do not top off the water instead of changing it. 


Frequency of water changing

During the early days of the aquarium hobby, fish lovers usually pour all of the water from a fish tank to do a water change once a month. But it is an unhealthy method because changing a large scale of water at one time is harmful to fish.

Fish are very sensitive, a big environment change will take time to adjust, if they can not adjust, they will get ill or die. And there will be much waste accumulating in one month, which will also influence the health of fish.

So how often and how much should you change the water? Generally speaking, you can change 10%-15% of the water once a week. If changing water every two weeks, you’d better change 20% of the water.

But it’s just a suggestion, you should determine it according to the fish you keep and the size of your tank. In the same circumstances, if your tank is larger, you can change less water or change it for a long time. If you keep more fish, you should change more water or change it more frequently.



A good filtration system is vital to an aquarium, however, the waste a filter can remove is limited and it will become less effective with time passing by. In order to maintain a healthy environment for your fish, a regular water change is also essential.

You may think it’s difficult and complex to do a water change, but if you follow the steps we mentioned before, you will find it very easy.

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