How to Change a Betta Fish's Water?

How to Change a Betta Fish’s Water?

Just like any other pet, betta fish require care and cleaning. Even though you can’t clean your fish directly, you still need to clean its enclosure. Since you can’t wipe down the enclosure as you would for other pets, you instead have to change water and vacuum the substrate.

Changing a betta’s water is both more complex and less difficult than most people think it is. While it may take thirty minutes a day to clean up after a dog or cat, it will only take about twenty minutes once a week to clean up after your betta. However, this clean up does include vacuuming, conditioning, and chemical testing, unlike a dog.

In this article, we will discuss nitrates, minerals, gravel vacuuming, conditioning the water, testing source water, and adding new water to the tank.


Nitrates aren’t going to help you change the water, but they will tell you how much water you need to change. This compound is the final stage of the nitrogen cycle, which must be completed in order to keep fish alive.

This final stage has the least toxic nitrogen compound, but it can still kill your fish if the concentration is too high. The typical concentration is between 20-40ppm, so you need to do water changes to keep them between 0 and 40 parts per million.

The most reliable test for nitrates is the API Freshwater Master test kit. While expensive, you will get more tests out of it than test strips, and it will be cheaper per test.

So, if you test your tank at the beginning of the week and you have 20ppm nitrates, but you test it at the end of the week and have 40ppm, this means that they increase by 20ppm every week. In order to keep them at safe levels, you will have to do a 50% water change every week.


Some people have tanks that consistently read 0 ammonia, nitrite, and nitrates. This may be due to bacteria that convert nitrates to nitrogen gas or excess plants. They may incorrectly conclude that this means they do not have to do any water changes.

However, there is more to water changes than simply nitrates. For most people, nitrates are a good rule of thumb, but for those without nitrates, they do still have to do water changes.

The primary reasons are minerals and Old Tank Syndrome. Water constantly evaporates from aquariums and leaves minerals behind. If you only top off the water without doing water changes, these minerals will build up in high amounts.

In addition, vital minerals will be used up, and the fish will not be able to get all that they need. If there are excess mineral buildup and a lack of essential minerals, you may have some random fish deaths and be unable to introduce new fish.

The inability to introduce new fish and keep them alive is a common symptom of Old Tank Syndrome. This occurs when there is too much mineral buildup in a tank. The buildup happens slowly over time, so the established residents can normally adjust to the freakishly high amount of minerals, but new fish will die, even if you drip acclimate them for hours.

The best way to fix this is frequent small water changes, between 10-15%, multiple times a day. This will gradually reduce the amount of minerals back to a normal amount.

Gravel Vacuum

Another vital instrument for cleaning your tank is a gravel vacuum or gravel siphon. These are generally ridged cylindrical tubes attached to a flexible tube. You plunge the rigid part into the gravel and it will remove all the trapped waste which then travels through the flexible tube into a bucket or sink or wherever you want it.

This makes cleaning much easier, as the mulm trapped under the gravel will continuously release nitrates until it is removed. It can also cause issues in tanks is too much accumulates.

The gravel siphon is a very effective tool for removing filthy water and waste from the tank. It’s fast, easy, and difficult to spill. They are also pretty cheap, only $8-15 depending on the size.

Most people use a bucket along with their gravel vacuum, as it is the easiest way to catch the water spilling out. Buckets are easy to transport and refill, and you can easily condition the water within the bucket.

Conditioning the Water

Water conditioner, also called dechlorinator, is vital for maintaining an aquarium if you have tap water, which 98% of the population does. In order to prevent water borne diseases such as cholera and keep the populous safe, the water is treated with chlorine and occasionally chloramines.

While these are incredible at preventing illnesses, they are incredibly toxic to fish. This is simply because the amount of chlorine needed to poison a human is much higher than the amount in tap water, but bettas are about the size of your thumb, so the amount in tap water is lethal to them.

Due to the toxicity of safe water, the water needs to be treated with a dechlorinator in order to make it safe for fish. On the other hand, if you know that you only have chlorine and no chloramines in your water, you can simply leave it out for 24 hours before adding it to your fish tank.

While some people have no problem with their fish and pure tap water, most people will have dead fish, or at least dead cycles. The bacteria that keep your nitrogen cycle going are more susceptible to chlorine than fish, but their death will result in massive ammonia and nitrite spikes, which can kill your fish.

Testing Source Water

In addition to chlorine and chloramines, your source water can also have other issues. The most commonly encountered ones are nitrates and ammonia. Both of these are toxic to fish, and if your source water has nitrates, water changes may become tricky, as the main reason for them is to remove nitrates.

However, if the water you are adding back into the tank is also full of nitrates, it will be difficult to continue keeping the nitrates low. You will have to use another method, whether it is aquaponics, nitrazorb, or excess aquatic plants.

On the other hand, the ammonia levels in tap water are often 1ppm or less, and this can be treated with Seachem Prime, which is a water conditioner capable of detoxifying up to 2ppm ammonia.

In addition, some water, especially well water, has a very high TDS, or total dissolved solids. These are typically caused by mineral deposits that the water comes in contact with, and the minerals dissolve in the water. This creates very hard water that only some species can live in.

Unfortunately, there is no way to fix this aside from getting a reverse osmosis unit or water from another source. Unlike soft water which can be used and remineralized, you cannot add anything that will remove the dissolved minerals.

Adding New Water to the Tank

When adding new water to a tank after a water change, there are only a few rules. One rule is that it has to be close to the tank water in terms of hardness, so suddenly switching source water is not a good idea.

The second rule is that the water must match the tank water in terms of temperature. The overall temperature of the tank water cannot change by more than 2 degrees during the whole water change.

The third is that the water must be treated, conditioned, and poured in gently and slowly. Bettas do not like high flow, so a sudden rush of water going into the tank can be too extreme for the bettas.

In conclusion, a betta’s water can easily be changed with a gravel siphon and bucket. While there are a few rules to follow when changing the water, they are simple. In addition, while it is important to test your water, you should be doing a water change at least once a week.

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