How Often Should You Change Your Aquarium Water? (Answered)

how often should you change your aquarium water

There is no doubt that doing water changes are important for maintaining the health and well-being of fish in an aquarium. However, not all people know how frequently and the amount they need to change the tank water. The wrong approach can lead to a drastic shift in the water parameters that kill your fish.

How often should you change your aquarium water? As a general rule, it is a good idea to change the water fish tank by 10 – 25% of the water weekly. However, This percentage is unstable as it depends on several factors, such as the nitrates level, the tank size, and the presence of live plants in the tank, etc.

Let’s keep reading to know more!

How Often to Change Water in Fish Tank?


Generally speaking, it is recommended to change 10 to 25% of the water each week.

The main purpose of changing water is to take water containing nitrates out and replace it with a clean one. It’s hard to give a certain water change schedule as every tank has its bio-load that leads to different water change schedules. The more fish and leftovers in the tank, the more waste there is.

To decide how frequently to change the water in a fish tank with a filter, you should first figure out how much waste your fish are producing by testing the nitrates level in the tank water.

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  • While the nitrates level of a normal fish tank should be kept below 40 ppm, the freshwater tank requires this parameter to be kept below 50 ppm. And fish will stay healthiest below 25 ppm in this freshwater fish tank water.
  • For example, if you notice the nitrates level in your 20 gallon fish tank hits 40-50 ppm, you need to perform a 25 – 30% water change.
  • So, by measuring the time your tank nitrates reach 40 ppm, you will know when to change water in fish tank.
  • Try not to perform more than 50% water change fish tank, even larger water changes sometimes seem to be better. A drastic water change can cause fish stress and lead to illness or death


In parallel with doing the water change, you can also keep the ppm low by adding some aquarium plants to the tank, feeding less, and not overstocking.

That’s about doing a partial water change in the fish tank, how about planted aquarium water change frequency? If you keep a planted aquarium, it is advisable to change at least 30% water every week to prevent waste and algae growth.

Are Aquarium Water Changes Necessary? Why?


No matter if it is a small fish tank or a large tank, performing water changes are necessary.

This process helps to maintain the proper balance of chemicals and nutrients in the water, and remove any buildup of waste products that can be harmful to fish and other aquatic life.

Fish and other aquatic life produce waste products, such as ammonia, which can build up in the water and potentially harm or even kill the inhabitants of the tank. Additionally, uneaten food and other debris can decompose, further increasing the levels of harmful chemicals in the water.

However, it’s crucial to find its own schedule of how often to change fish tank water, too often water changing can cause fish to stress and get sick. Be careful!

Frequently Asked Questions

Can you change aquarium water too often?

In some cases, it is possible to change the water in an aquarium too often, like once per day and 2 days in a row.

However, you still need to know that changing the water too frequently can disrupt the delicate balance of chemicals and nutrients in the water, which can be harmful to the fish and other aquatic life in the tank.

It’s also important to remember that never do a full water change in fish tank, less than 50% is best.

When to do first water change in new aquarium?

It’s advisable to do the first partial water change from 20 to 25% after two weeks when the tank has been set up with full equipment.

Before doing a water change or adding any fish to the tank, test water parameters to check if the tank is cycled. You can use a test kit to measure pH, nitrite, and ammonia levels.

Doing this also helps you understand the tank’s water parameters, as well as make any necessary adjustments to maintain a healthy and balanced environment for the fish.

How do I change the water in my fish tank without killing the fish?


Step 1. Use a test kit to test the aquarium water parameters to have a sense of how much water percent you should be removing.

Step 2. After determining how much water you are swapping out, you’re going to turn off all electrical equipment until the changing water process is finished.

Step 3. Then, scoop out water from your fish tank to a bucket using a clean cup, or a dedicated water-changing product. This outgoing water can be used to rinse filter media or decorations…

Step 4. Before adding water to fish tank, remember to use a water conditioner to dechlorinate new water. Now you can add new water to the tank!

Also, you can use an aquarium water changer to do this task easier.

How often should I change aquarium water for goldfish?

You should change 30% of the water in your goldfish aquarium weekly respectively. It is important to note that conducting a 100% water change can stress or harm your fish, and change the water chemistry suddenly.


How often should you change your aquarium water? The number of times you should perform water changes in your fish tank can be decided based on specific factors including the nitrate level.

Normally, it is recommended to do a partial water change of 10-25% of the tank’s water every 1-2 weeks. Remember to use a water conditioner to remove chlorine from tap water before adding it to the tank.