How Often To Change Betta Water: Complete Beginner’s Guide (2024)

Dr. Mollie Newton
Published by Dr. Mollie Newton PHD| Senior Editor
Last updated: May 9, 2024
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The arena of betta fish maintenance is incredibly engaging. It extends from establishing your initial aquarium to the sheer delight of observing these vibrant and intriguing tiny swimmers as they investigate their space within your home. It’s a highly gratifying and absorbing encounter. Yet, it’s crucial to remember that we carry the responsibility of protecting these fish and their man-made habitat.

Article Summary

  • Water changes help mimic the natural processes that occur in the Betta fish’s natural habitat, such as nutrient uptake and waste removal.
  • Proper materials and tools are needed for a successful water change, including a water test kit, pH adjusting reagents, dechlorinator, tank siphon, bucket, and thermometer.
  • To keep the tank water clean and healthy for Betta fish, avoid overfeeding, overstocking the tank, and regularly clean and maintain the filtration system.

When it comes to weekly chores like water changes and filter cleanings, we as responsible aquarists must do our best to keep things safe and clean for our aquatic friends.

If you’ve ever wondered how to perform a water change, how often to change betta water, or even what a water change can do for your betta tank, read on for the answers to these and more questions in today’s article on betta fish.

Why Are Water Changes Important?

A Small Fish Tank with Blue Betta
A Small Fish Tank with Blue Betta

Water changes play a vital role in the overall health of your betta fish tank. Considering that we are creating an artificial environment and filling it with all sorts of fish, fish tank substrate, heavy plants, and invertebrates, it’s essential to avoid stagnation and the buildup of harmful chemicals within the betta fish’s tank.

Imitating a Natural Process

Where the betta fish live, in their natural environment of rice paddies and small bodies of tropical water in Southeast Asia, actions such as currents and underground water flow allow even still-looking water to have some form of movement.

This creates an influx of new nutrients and minerals, while allowing pent-up waste materials such as decaying matter and fish waste to exit the system.

In our home aquarium, we, therefore, do our best to mimic this natural system. By removing some portion of the water from our tank and adding in new water, we foster the uptake of nutrients and the removal of potentially dangerous chemicals to ensure your betta remains healthy and for them to reach their maximum size.

Additionally, we allow good bacteria the chance to become more established and help our fish and live plants.


Without regular tank water upkeep and maintenance, toxic shock can result for your betta fish. This harmful condition means that ammonia has overwhelmed their natural immunities, meaning decreased resistance to disease and infection, along with damage to the circulatory system.

How Long Can A Betta Fish Go Without Water Change?

A few factors influence how long a betta fish can live without a water change, including the quality of your betta aquarium setup.

If you have a smaller aquarium size of less than 10 gallons, you’re much more likely to see the negative effects of water stagnation happen more quickly than a larger tank. In as few as 1 to 2 days, nitrate levels in an unfiltered bowl can rise to dangerous levels and poison your fish. Having an appropriate filter for your betta tank can help keep water parameters healthy.

Siamese fighting fish in a fishbowl
Betta in a Fish Bowl

Larger tanks with an adequate fresh water filter and well-established colony of beneficial bacteria to reduce ammonia will tend to fare better. At the bare minimum this hypothetical well filtered tank could go for upwards of a week without seeing much change in the quality of the betta’s water.

However, after this point, the ammonia and nitrate levels would likely still be too much for the closed system and you’d begin to see negative effects such as illness and infection.


These labyrinth fish are especially adapted to breathe air and are much hardier than other fish when it comes to poor water quality, meaning other creatures in your tank may still be suffering even when your betta seems fine.

Regular water changes at least every week reduce the change of any issues happening in the first place!

How Often To Change Betta Water

Again the answer to this is somewhat dependent upon the size of your betta tank (or betta bowl) and the conditions within it.

Smaller tanks with less established filter systems, tank lights, and more tank mates may need more frequent water changes while those with good mechanical and biological filtration will likely need less.

As a general rule of thumb, change your betta tank water every week or so, around 7-10 days. This will keep dirty water from becoming a problem, and allow the wastes released from your fish and things like uneaten food and decaying plants to exit your tank.


While it is absolutely essential to change the water every now and again, doing so too often or with too much water at one time can be harmful for your tank. This is because the beneficial bacteria in your tank can be removed with the old water, resetting the nitrogen cycle in your tank and potentially killing your fish!

What You Need To Change Betta Fish Water

Before you go ahead and start taking water directly out of your fish tank and putting in new fresh tap water, there are a few pieces that you’ll want to make sure to have in place.

Starting a water change and suddenly realizing that you don’t have the proper materials can really leave your betta’s tank in a bad spot!

Fish Tank Being Filled with Water
Fish Tank Being Filled with Water

Most of these options should be available from your local pet stores or favorite online vendor.


As somewhat of a side note, consider purchasing a tank cover for your betta fish tank. Bettas, and especially male betta, are jumping fish and may get the natural signal that it is time for them to vacate when conditions are changing in your tank!

Water Test Kit

An essential part of any betta aquarium caretaker’s arsenal, these handy kits allow you to determine the chemical makeup of the water in your fish tank.

Some may test for different things than others, but in general they tell you the pH, water hardness, and level of dissolved ammonia in your tank.

pH Adjusting Reagents

Known as water conditioners, these typically come in drop form. They adjust the pH of your tank by binding to free floating molecules of hydroxide and raising the pH (thus making it more basic,) or by adding an acidic element to lower it.


Betta fish generally prefer a more neutral water pH, from around 6.5-7.5.


Given that many forms of tap water come with added chlorine for use as drinking water, a dechlorinator is often necessary to keep your betta healthy. These are best used prior to adding to your betta’s water so that you can make sure everything has taken effect before adding to the fish tank. Make sure to not overuse dechlorinators as they can be harmful to your betta.


Placing tap water straight into your fish tank is a surefire recipe for burn-out gills and disease for your sensitive bettas!

Tank Siphon

Man Changing Water in Aquarium Using Siphon
Man Changing Water in Aquarium Using Siphon

A tank cleaning siphon hose allows you to remove water from your tank safely, without worrying about accidentally hurting your betta fish or other aquarium denizens.

These typically have a squeezable bulb attached to a long siphon hose tube with a small opening, allowing you to pull water out of your betta tanks without drawing any fish with it.


While it may seem somewhat basic, having a bucket to allow tap water to splash into or providing a space for you to add water conditioner is essential. You’ll generally want one bucket to empty the old water and one to mix the new clean water in.


Temperature control is a key part of the process of a water change. You’ll want the water that you’re adding to be as near as possible to being the same temperature as your betta’s fish tank.

Having a thermometer for the tank and another for the water to be added will ensure that you have the most accurate readings possible prior to changing anything in your tank.

Given that bettas are tropical fish, whether you add warm or cool water can make the difference between a quick, easy transition and potential temperature shock.

Bettas thrive best at temperatures between 75 and 80 degrees Fahrenheit…

Bettas thrive best at temperatures between 75 and 80 degrees Fahrenheit, meaning that you will likely need to consider heating the water and measure it with a tank thermometer before adding it into your tank.

How To Change Betta Fish Water Tank

Arranging Fish Tank Decorations
Arranging Fish Tank Decorations After A Water Change

There are three primary steps to changing your tank’s water, with different component actions in each. We’ll want to first prep the replacement water, then remove the dirty water from the tank, then finally add in the new clean water and monitor for changes.

Preparing Replacement Water

  • Pull out the amount of clean water that you’re looking to replace from your water source. If using something like tap water, consider allowing it to sit for 2-3 days so that excess chemicals can offgas. Be sure to use a completely clean container to avoid obvious issues with contamination.
    • When determining how much water to replace, consider that in general you’ll want to replace about 10-15% for a weekly change, or 20-25% if waiting for longer. This means that for a 10 gallon tank, you’ll want to add in one gallon of new water with a weekly partial water change
  • Add in your water conditioner to the clean bucket and allow it to mix for the required amount of time (typically stated on the container) in order to remove chlorine and establish a neutral pH level
  • Use a test kit or test strips to ensure that the conditions of the clean water are adequate, and that the temperature is close to that of your tank

Remove Old Water

  • Using your suction hose, remove the required amount of water from your tank and into the dirty water bucket (ie 1 gallon for a 10% change in a 10 gallon tank, etc)
    • For a heavily planted tank, be sure to avoid accidentally lowering the water line below their required amount. Going slower is always the best option when you have questions!

Add New Water To Tank

  • After ensuring that water conditions are adequate in terms of pH and temperature, gently pour the treated water from your clean system into the main tank
  • Continue to test the water in your tank for the next few days, monitoring your fish for unusual symptoms or behaviors such as swimming on the bottom of the tank, swelling, and redness, which can all indicate that something is off

For more betta water change tips, watch this video below.

How To Do A Water-Change On A Small Betta Tank

Tips To Keep Tank Water Clean

Avoid Overfeeding

While it is of course important that your betta eats the proper amount of food, having leftover food sitting in the betta’s container can quickly become a problem. This extra food decays, releasing ammonia and nutrients into the water that can cause problems like algae blooms and even toxic shock.

It’s a good idea to monitor your fish while feeding and remove uneaten fish food….

It’s a good idea to monitor your fish while feeding and remove uneaten fish food within 30 minutes after feeding. This will ensure that your small tank isn’t overwhelmed by harmful chemical buildup.

Avoid Overstocking

Having lots of neighbors like plecos and mystery snails can make our tanks look much more friendly and home-like, but it also comes with its own set of problems.

Each fish and invertebrate produces its own waste, which can rapidly spiral if you don’t have adequate filtration or water movement in your tank.

Check Your Filters

If your betta lives in a filtered tank, keeping your filters clean, and replacing them when they no longer function properly is a key part of maintaining a healthy cycled tank.

Sponge filter media can quickly become a place for harmful bacteria to multiply if they aren’t cleaned regularly, largely defeating the original purpose. Follow a set schedule with regard to cleaning and you should be set up for years to come.


When it comes to performing regular water changes, there are definitely some important things to keep in mind to maintain a healthy environment for your betta fish.

Letting things go for longer than a week between changes can allow harmful chemicals and wastes to accumulate, increasing the risk of disease and harm to their gills and circulatory system.

Make sure to properly test and monitor your water before and after each change to ensure that the transition has been a smooth one.

Feel Free To Share

As always I hope that you’ve enjoyed today’s article about how often to change betta water, and that it has answered all of your betta water change questions. Feel free to share this information with any fellow fish keeper you may know, and I wish you the best of luck on your continued aquarium adventures!

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