How Often To Change Aquarium Water: Best Methods & Reasons

how often to change aquarium water
Japanese Fighting Fish is reader-supported. When you purchase through one of our links we may earn an affiliate commission (at no extra cost to you).

A beautiful aquarium can be a great addition to your home, office, or classroom, providing a visual and auditory centerpiece that can brighten up any room.


While they are generally low-maintenance, one of the most important things you can do for your aquarium is to perform regular water changes.

Changing the water in your aquarium removes harmful toxins and debris and replenishes essential nutrients. Also, the beneficial bacteria convert toxic ammonia excreted by fish into nitrate.

Thus keeping your pet fish healthy and happy. How often are you supposed to change the water in your aquarium? Read on to find out.

How to Change Aquarium Water

There are a few different ways to change the water in your aquarium, but the most important thing is to do it slowly and carefully to avoid shocking or harming your fish.

The Gravel Vacuum

vacuum gravel in an aquarium

The most effective and easiest way to change your aquarium water is to use an aquarium gravel vacuum. A gravel vacuum is a simple hand-held device that you can use to remove debris, uneaten food, and waste from the gravel at the bottom of your tank.

To use a gravel cleaner, place the suction end into the gravel and slowly move it around the tank, careful not to disturb any plants or decorations. As you vacuum, you will suck up the water into the tube. Once you finish vacuuming, remove the tube from the aquarium and dispose of the water in a sink or outside.

The Bucket Method

siphoning aquarium water using hose

It can be a bit more time-consuming, but you can also change your aquarium water using the bucket method. You will need a clean bucket and an aquarium-safe hose. To start, use the hose to siphon out about 20-25% of the water from your aquarium into the bucket.

Next, use a clean sponge or rag to wipe down the inside of the tank, being sure to remove any algae buildup or accumulated debris. Once the tank is clean, you can begin to refill it with clean, fresh water and if you are using tap water, treat it with a de-chlorinator before adding it to a new fish tank.

Once your tank is full, you can add any plants, decorations, or fish removed during the cleaning process.

Why Change Aquarium Water?

cleaning the aquarium

Aquariums are a closed system, meaning that the water in your tank will eventually become polluted with toxins such as toxic ammonia and fish poo.

These toxins will eventually affect your aquatic friends, causing them to become sick or even die.

You can remove these toxins and debris from your aquarium by performing regular water changes and keeping your fish healthy and happy. In addition, water changes also replenish essential nutrients that are necessary for the health of your fish and plants. These nutrients can become depleted over time, so it is important to replenish them regularly.

How Often to Change Aquarium Water

aquarium with lots of fish

How often to change fish tank water will depend on several factors, including the number and type of fish you have, the size of your tank, and the level of biological filtration you are using. A large aquarium with many fish will need to change the water more frequently than a small tank with fewer fish.

It is recommended that you change 20-25% of the water in your aquarium every 2-4 weeks. However, how often to change the water in your fish tank may depend on the specific needs of your tank. For example, if you have much fish or live in an area with hard water, you may need frequent water changes.

The nitrogen cycle in your tank will affect how often to change aquarium water. If you have a well-established tank with a healthy nitrogen cycle, you may be able to go longer between water changes. However, if you have a new tank or your nitrogen cycle is not yet fully established, you will need to have a regular water change.

A 40 ppm or less nitrate level is considered safe for most fish.

But you may want to keep your nitrate levels even lower if you have sensitive fish or are breeding fish.

The best way to determine how regularly to change your aquarium water is to test it regularly with a quality freshwater test kit. This will allow you to observe the levels of toxins and nutrients in your tank and make adjustments to your water change schedule as needed.

Fun Fact: Betta tanks need regular maintenance and this includes periodical water changes. Learn tips and hints from our post. Read here — How Often To Change Betta Water? We Flush Out The Details!

Things to Keep in Mind

When changing the water in your aquarium and how often should you change fish tank water, you should keep a few things in mind. They are:

Change the Water Gradually

aquarium with water

Sudden changes in the water chemistry or temperature can shock or even kill your fish.

To avoid this, always change the water gradually over the course of an hour or more. This will ensure that your fish will have time to adjust to the new conditions and minimize the risk of shock.

Use Clean Water

Salty water, dirty water, or water with high levels of toxins can harm your fish. Be sure to use clean, treated water when performing a water change.

Use An Aquarium Vacuum

cleaning aquarium with vacuum

An aquarium vacuum, also known as a gravel vacuum, is a useful tool for performing water changes. Aquarium vacuums can help remove debris and waste from your gravel and substrates, making your tank cleaner and healthier.

They can also help remove toxins and excess nutrients from your water, making it safer for your fish. Aquarium vacuums are relatively inexpensive and can be found at most pet stores.

Do Not Overload the Filter

A filter is an important part of any aquarium, and it is essential for keeping your water clean and healthy. However, it is crucial not to overload the filter with too much waste.

If the filter becomes overloaded, it will no longer be able to remove toxins and waste from your water effectively. As a result, your water will become polluted, and your fish will be at risk. Always perform regular water changes and clean your filter regularly.

Monitor Your Fish

Your fish is the best indicator of the health of your aquarium. Be sure to monitor them closely and look for any signs of stress or illness.

Look for any signs of stress, such as increased respiration or listlessness. 

Also, look for any physical signs of illness, such as white spots or red lesions. If you notice any of these signs, be sure to take action immediately. Perform a water change, clean the filter, or consult a veterinarian if necessary.

How to Reduce Frequency for Water Change

Below we have compiled a list of a few things you can do to reduce the frequency of water changes.

A Larger Filter

Having a larger aquarium filter media will help keep your water cleaner for longer periods. A larger filter will have more surface area for bacteria to grow, and it will be able to filter more water more effectively. This will help to keep your water cleaner and healthier for your fish.

Live Plants

Live plants are a great way to ensure that your water is clean and healthy. Plants help to filter the water and remove ammonia and nitrates.

They also help to oxygenate the water, which is essential for the health of your fish.

Aquariums with live plants typically require fewer water changes than those without.

Perform Partial Water Change

Partial water changes are often a great way to keep your water clean and healthy. Instead of performing a complete water change, you can remove some water from your tank and replace it with fresh water.

This will help remove some toxins and waste from your water while also maintaining the same water conditions for your fish. You should perform partial water changes weekly.

Monitor Your Fish Food

The food that you feed your fish can also impact the health of your aquarium. Look for any signs of contamination or expiration date.

Also, be sure to feed your fish the proper amount of food. Uneaten fish food can lead to excess waste in your tank, polluting your water and harming your fish as they can not live in their own waste.

Regular Maintenance

Ensure that you are regularly maintaining your aquarium environment. This is done by cleaning the gravel, vacuuming the substrate, and cleaning the mechanical filter media.

Regular maintenance will ensure that your aquarium is clean and healthy. It will also reduce the regular water change.

Automatic Water Change Systems

Automatic water change systems will ensure that your water is always clean and fresh. These systems will automatically remove water from your tank and replace it with fresh water. They are also very convenient, as they will do all the work.

Protein Skimmers

Protein skimmers are devices that remove fish waste and toxins from your water. They are often used in saltwater aquariums, but you can also use them in freshwater tanks.

These Protein skimmers are placed in the aquarium’s sump, and they work by removing waste and nitrates from the water before it enters the main tank. They are a great way to keep your water clean and healthy.

Reverse Osmosis Filters

Reverse osmosis is one of the purest forms of filtration. Reverse osmosis filters remove impurities from your water by forcing it through a semi-permeable membrane.

This process removes many impurities, including heavy metals, algae, chemicals, and toxins. Also, adding RO water or distilled water helps reduce the hardness of the water. This will also help in maintaining the cleanliness of the tank.

Monitor Your Tank

Be sure to monitor your fish tanks closely. This includes testing the water parameters regularly and observing the fish for any signs of stress or illness.

By monitoring your aquarium, you can quickly identify any problems and take steps to correct them. This will help to keep your aquarium healthy and thriving.

Fun Fact: Complement this excellent reading material with our post on How To Get Crystal Clear Aquarium Water: Top 4 Fish-ful Ways for a fuller understanding of this article’s subject matter.

Related Questions

What are some of the best plants for aquariums?

Some of the best aquarium plants include Java ferns, Hornwort, and Anubias. These plants are easy to care for, and they can help keep your aquarium water clean and healthy.

What is the best fish food for aquariums?

The best fish food for aquariums is a high-quality, nutritious diet specifically designed for aquarium fish. Be sure to avoid overfeeding your fish, which can lead to excess waste and pollution in your aquarium.

How can I prevent old tank syndrome?

The best way to prevent old tank syndrome is to maintain your aquarium and change the water regularly. Also, monitor your fish food closely and look for any signs of contamination.

The ideal water chemistry for my aquarium?

The ideal water chemistry for your aquarium will depend on the type of fish you have. Freshwater fish generally prefer neutral to slightly acidic water, while saltwater fish generally prefer slightly alkaline water. Before making major changes to your aquarium’s water chemistry, be sure to ask a professional.

The Bottom Line

Aquariums offer a great way to relax and enjoy the beauty of fish. However, they do require some maintenance to stay clean and healthy.

Water changes, regular cleaning, and monitoring are essential parts of aquarium care. These simple steps can ensure that your aquarium is a beautiful and healthy environment for your fish.

Last Updated: July 13, 2022