How Often To Change Betta Water? We Flush Out The Details!

how often to change betta water
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Any experienced fish keeper knows that changing aquarium water is essential to keep your fish alive and kicking. Not only does this replace the water that has evaporated over time, but it also removes wastes and toxins that can be harmful to your fishies. 

That’s really important!

So, when it comes to Betta fish, how often should you change their tank water? Once a week? Twice a week? Or does the period vary from one tank to another? Keep on reading to discover all you need to know about Betta fish water changes, from why it’s necessary to how to do it.

Optimal Water Conditions For Bettas 

Thankfully, Bettas are hardy little creatures. This makes them an ideal fish for inexperienced fish owners as they can survive in a variety of conditions.

In fact, when seen in the wild, Betta fish live in warm, shallow, and slow-moving waters with such a low oxygen content that’s normally lethal to any other fish.

However, Bettas are able to overcome these conditions due to their labyrinth organ, which gives them the ability to breathe the same air we breathe. 

So, if the water oxygen content gets low, a Betta fish will simply rise to the surface and take a breath. 

Fascinating, isn’t it?

So, we now know that Bettas like warm waters that can be high or low in oxygen. What else?

Well, pH-wise, Bettas like water with a neutral pH. Yes, they can survive in slightly acidic and even alkaline conditions, but a neutral pH will make your fish the happiest and healthiest. 

When it comes to water hardness, Bettas prefer soft water with a lower general hardness (GH) and carbonate hardness (KH). So, keep the dissolved minerals to a minimum, and always try to add some plants to a betta’s tank. Not only are these plants capable of producing oxygen for your fish, but they also act as a filtration system that consumes fish waste products. 

So, to sum up, a Betta fish tank should have a scattering of plants and it should be filled with warm, neutral, soft water. 

Optimal Water Conditions For Bettas 

Why Should You Change Your Betta’s Water?

Now, as hardy as Bettas can be, their health will begin to suffer if they’re left in less than optimal conditions for a long time. Sure, they’ll survive for quite a while as they can breathe air from the surface, but they won’t exactly thrive. That’s because, with time, nitrogenous wastes accumulate in the tank and start messing with the Betta’s health. 

To illustrate, the three wastes of major concern are ammonia, nitrite, and nitrate. These wastes typically arise from uneaten fish food, fish wastes, and decayed plants.

Now, ammonia is the most toxic chemical. Thankfully, though, it’s easily broken down by certain beneficial bacteria residing in your tank filter into nitrite, which is less toxic. Nitrite is then broken down into nitrate, which is even less toxic, and this is what’s known as the nitrogen cycle. 

Unfortunately, unless you’ve got yourself a heavily planted tank, nitrate will accumulate in the tank until it reaches levels harmful to your fish. The high nitrate levels will also increase the water acidity until it gets too much for the fish, and they’ll start becoming lethargic and sickly.

Accordingly, the only way to get rid of the excess nitrate is to change your Betta’s water.

 Change Your Betta's Water

How Often Should You Change Betta Fish Water?

Well, if you want an easy answer, then once a week should do it. However, the real answer is a bit more complicated than that. That’s because there are a number of factors that’ll affect how often you should change a betta’s water. So, let’s see what those factors are, shall we? 

Tank Size 

In case you weren’t aware, larger tanks require fewer water changes than smaller ones. Why’s that, you ask? Because the more water you have, the longer it’ll take for the water chemistry to change. So a large tank will have a more stable pH, temperature, etc., for a longer time when compared to smaller tanks. 

So, it’s totally fine if you’re planning on getting a smaller tank for your Betta (say a 2.5-3 gallon tank). However, keep in mind that you’ll need to perform more frequent water changes. You’ll also need to keep a close eye on your water parameters, as any alteration in the water quality will necessitate a water change. 

As such, inexperienced fish keepers should get themselves a larger tank, as a small tank will be much harder to maintain.

And now that you know which tank size to get, how much water should you take out at a time?

Well, as a general rule for tanks of any size, small and frequent water changes (10-20%) are better than large, infrequent changes. That way, you don’t suddenly cause a radical change in the water chemistry.

To illustrate, say your tank water has reached a pH level of 6.5. If you replace a large amount of the tank’s water with fresh water, the pH will suddenly rise by a significant amount, which can stress and even kill your fish.

So, go to the extra trouble of regular water changes as this is the best way to not stress your beloved Betta fish.

Tank Size 

Tank Filter

First off, you should know that Betta fish can survive without a filter.

However, a tank with no filter necessitates more maintenance. In fact, if you’ve got yourself a filterless 2.5-gallon tank, you’ll need to replace small increments of water every single day. That’s because an unfiltered bowl will be rapidly filled with toxic materials, namely ammonia and its metabolites, which will need to be removed as fast as possible. 

That’s why it’s best to get a filter for your Betta tank. Not only will it oxygenate the water, but it’ll also break down the harmful wastes present in it, giving you more time between water changes. 

Still, you should keep in mind that certain filters are better for Bettas than others. 

For example, undergravel filters aren’t great as they can trap wastes and debris under the gravel.

Powerful filters like hang-on-back and canister filters are also not that great for Betta tanks. That’s because they create strong currents that hinder the Bettas when swimming. 

That being so, a sponge filter will be perfect for a Betta tank as it doesn’t affect the water flow that much.

Oh, and by the way, real plants can be a great addition to your tank. They act as a natural water filter, tackling the high ammonia and nitrate levels of the entire tank. Still, keep in mind that they won’t be able to entirely purify the water, so a sponge filter is still the filter of choice if you’re looking to decrease the amounts you change Betta fish water.

Tank Filter

Feeding Amount And Frequency

If you overfeed your Betta fish, then you’ll need to change your water more regularly. That’s because the more a Betta eats, the more waste it produces. Moreover, any leftover food will start decaying, resulting in high toxin levels in your Betta aquarium.

How often and how much should you feed your bettas? In short, since Bettas aren’t very active, they don’t need that much food; just one hearty meal will be enough. 

Give them enough to make their bellies round and leave them alone for the rest of the day.

However, if you want to interact more with them, then you can give them three small meals spread out throughout the day. Don’t give them more than they can eat in a single feeding, and don’t feed them too often. If you don’t do this, you’ll need to change your Betta’s water more than once a week.

Feeding Amount And Frequency

Tank Mates

As you know by now, Bettas are quite sturdy. However, other fish aren’t built to withstand harsh water conditions. So, if your Betta has some other tank mates, you’ll need to make more frequent water changes to give the other fish a fighting chance. This also applies if you’ve got baby Bettas in the tank.

Tank Mates

How To Change Betta Water 

Thankfully, changing a betta’s aquarium water isn’t that difficult as long as you’ve got the right tools. These include things like a tank cleaning siphon, water conditioner, and tank thermometer, to name a few. Add these tools to a couple of buckets, and you’re all set. So, let’s see how exactly you should change Betta water:

Remove The Dirty Water 

Remove The Dirty Water 

The first thing you need to do is remove the tank cover and take out a good amount of the old water filled with harmful chemicals. But, before you do this, you should start cleaning your tank walls and allow any debris to settle at the bottom of the tank.

Once the water has settled and you’ve removed all decorations in your tank, get the siphon hose and start dragging it across the tank floor. This will get the water flowing out of the tank and into the bucket you have waiting.

Just make sure to keep an eye on your fish while you’re siphoning the water, as even a robust male betta can get sucked up in the current.

Treat And Put In Replacement Water 

Treat And Put In Replacement Water 

Now that the water is out, you’ll need to put in some fresh water. Unfortunately, you can’t just use tap water and call it a day. That’s because our drinking water is filled with chlorine and other chemicals that will harm the bettas. Accordingly, you’ll need to fill a clean bucket with fresh tap water, then use a water conditioner to make the water safe for your Betta fish. 

Once you’re done with this step, get out your water test kit and examine the pH, GH, and other parameters of the replacement water. If they don’t lie in the proper range for a betta, then use pH-adjusting reagents and other water modifiers to correct the levels. 

Finally, take out your thermometer and see if the new water has the same temperature as the tank water. If it’s not, add warm or cool water until you hit the right number, then gently pour the water into the tank, and you’re all done.  

Watch This!


Provided you have a large, filtered tank for your bettas; you should replace about 20% of the water once a week. This is so that your Betta remains healthy and happy. Larger changes of about 30% can be done every few weeks, but they’ll be more stressful to the Betta fish. 

Nevertheless, if you’ve got an unfiltered tank that’s on the smaller side, then you’ll need to take out these large amounts every few days. Still, you can always use a water test kit to see what parameters you’re working with and then decide how often to change Betta water.

Last Updated: July 28, 2022