How Often Should You Change Your Fish Tank Water?

The aquarium is a closed system, so you have to ensure that everything in your aquarium is perfect for your aquatic creatures as an aquarist.

Changing the water is one of the essentials of your aquarium maintenance. But water changes need to be done correctly at a reasonable frequency.

With that in mind, you might wonder, “How often should you change your fish tank water?“Let’s read on to get the correct answer!

How Often Should You Change Your Fish Tank Water?

We recommend changing 10 to 15% of the water per week. If your aquarium is heavily stocked, it is okay to bump that up to 25% per week.

You can do water changes for lightly stocked tanks every two to four weeks, provided you track it carefully.

Doing too many water changes in your aquarium is possible. But the maximum frequency of water changes is once each day.

If you plan to do water changes daily, we recommend replacing half of your tank’s water to avoid disturbing your aquarium’s biological balance and stressing fish.

group of fish in tank

Why Do You Need to Change Your Fish Tank Water?

Changing the water allows you to refresh water containing toxins and waste with clean water.

It deals with the nitrogen cycle, where leftover food, decaying plant matter, and your fish are a source of ammonia.

If the nitrogen cycle functions excellently in the aquarium, it should have zero ppm ammonia, zero ppm nitrite, and no more than one hundred ppm nitrate.

It is ideal as nitrate isn’t as toxic as ammonia en nitrite if it is kept in low concentrations.

Although nitrate isn’t as toxic as other substances, it will gradually build up over time. So you don’t want this substance to hit levels that will harm your fish.

Can You Do Fewer Water Changes When You Have Live Plants?

live plants in tank

Live plants may help you in removing ammonia and nitrate from the water. So they will contribute to cleaning the aquarium.

Yet, keeping live plants in an aquarium is not a substitute for water changes.

Instead, they allow you to change the aquarium water less often. It may be once every two weeks or once every three weeks.

Aquarium Water Change Steps

Step 1: Ideally, change your aquarium’s water with dechlorinated water.

Then leave it to sit for one day to dissolve dissolved gasses like any chlorine, enabling the water to hit room temperature.

Step 2: When changing your tank’s water, you should vacuum the tank’s substrate to remove as much detritus as possible.

Step 3: Avoid cleaning your filter when doing a water change and vacuuming the gravel.

Both the gravel and the filter harbor have good bacterial colonies. So disrupting both at the same time may harm your aquarium’s healthy biological balance.

You should clean the filter a few days after or before changing the water.

Bonus Tips To  Change Your Fish Tank Water

Vacuum the Substrate: When changing the tank water, vacuuming the substrate is wise to remove detritus that accumulates at the bottom of the tank.

Beneficial Bacteria Colonies: Healthy bacteria are essential for a great aquarium.

So avoid removing too many beneficial bacteria since it will disrupt your aquarium’s chemical equilibrium.

The simplest way is to clean the gravel and the filter on different days.

Always Treat the Water: Tap water contains chemicals like chlorine and ammonia that are harmful to your fish.

So treating the water before introducing it into the tank is essential. Many products are available that allow you to treat and neutralize these chemicals.

Disable the Aquarium Lights: Doing a water change can be a stressful event for your fish. So after doing a stressful water change, it is possible to calm your fish by turning off aquarium lights for several hours.

Don’t Clean Your Filter: We recommend avoiding keeping the filters squeaky clean. Rinse your filters once per month is okay but ensure you do not overdo it.

Learn About Fish: General guidelines for changing aquarium water generally work well for most fish. However, you should learn about your fish and tailor the water change routine to its needs.


Can You Change Aquarium Water Too Often?

There is no limit on how often you can change the water in your tank.

But the maximum frequency of water changes should be once each day. You can change the water daily to remove excess food and encourage maximum growth.

Can Massive Water Changes Kill Fish?

A large, sudden water change will cause a drastic shift in the water parameters that your fish often can’t tolerate and die.

Those that don’t die immediately will be stressed and may struggle with the disease over the next few weeks.

Should I Change My Fish Water Every day?

Yes, you can. But we recommend replacing half of the tank’s water to avoid disturbing the aquarium’s biological balance and stressing your fish.

Can I Add Water Conditioner While the Fish Are in the Tank?

Adding a water conditioner to the tank will not kill your fish unless you exceed the recommended dosage. But a lot of water conditioners can kill your fish.

How to Change My Tank Water Without Killing My Fish?

Ensure you don’t disturb the beneficial bacteria on the substrate and in the filter. Those bacteria break down ammonia into nitrate.

If disturbing them, they won’t be able to break down ammonia, and your aquarium water will become toxic.

The Bottom Line

Through the above article, we helped you answer, “How often should you change your fish tank water?

If your tank is averagely stocked, doing 15 to 20% water changes per week is best. You can do a weekly 20 to 30% water change for a heavily stocked tank.

Thanks for your time!