How Often To Change Betta Water (for a HEALTHY Betta)

It is important to change the water of your betta fish’s tank regularly to ensure they remain healthy. This will stop harmful ammonium and nitrate levels from building up.

In tanks smaller than 2 gallons, you should change the water completely several times per week. If you have at least a 2 gallon tank, you can get away with a 50% water change once per week. The smallest size tank that is ideal for a betta, though, is a 5 gallon tank, and you can do a 25-30% water change once per week in that sized tank.

Let’s discuss changing your betta’s water in more detail.

How often to change betta water

How often should you change the water?

How often to change your betta fish’s water varies according to the tank size. Here is a table breaking down what percentage of your water to change and how often for each size of tank

Size How Much How Often
< 1 Gallon 100% Daily
1-1.5 Gallons 66% 2x Per Week
2-4 Gallons 50% Weekly
5-9 Gallons 30% Weekly
> 10 Gallons 25% Weekly

If you have a very small, 1-pint jar this should be changed every day. We do not advise keeping a betta in a bowl this size. 

If the tank is 1 quart, this should be changed completely every day. A half-gallon bowl should also be changed completely every day. A 1-gallon tank should get a 2/3 water change twice per week. These sizes also aren’t ideal for betta to live in long term.

Larger tanks of 2 to 3 gallons (small home aquariums) should only ever have 50% of the water changed at once. This should happen once per week.

A large home aquarium of 5 to 10 gallons should not have more than one-third of the water changed at any one time.  (This is the smallest size of tank I recommend you keep a betta in.)

Depending on whether you just have a betta or you have other tank mates, you can do either a 25% or 30% water change

This should happen once per week, meaning that the entire tank gets replaced with fresh water once a month. 

The exception to this is if you are raising newborn and young betta fish. In this instance, you should do a smaller water change every day, ideally. This kind of environment will help your betta fish to grow optimally. 

The most important factor to observe is the ammonia level in the tank’s water. This is toxic to fish and you should purchase test strips to keep an eye on the water concentration. 

When else should the water be changed?

If you are using water-soluble medication you are likely to need to change the water in the tank more frequently.

There are some medications that are more effective in clean water and in this case, they should be changed every 24 hours. 

If the water appears dirty, has a lot of scum, or is cloudy this is a good sign that it needs changing. Water like this is bad for the health of your betta and they should not live in this kind of environment. 

If you have overfed your betta and there is a lot of excess food in the tank this can begin to decay. This will cause the water to fill with toxins and should be avoided. 

What do you need to change the water?

You will need 2 large buckets. One should be completely clean and chemical-free – this will be used to hold the new water to add to the fish tank. The other bucket will be used to collect the waste water from the tank.

We recommend purchasing a tank cleaning siphon as this is the most efficient way to clean the tank. It drains water and vacuums loose debris without disturbing your betta fish.

You will also need some kind of water conditioning solution which helps to remove the chlorine and fluoride from household tap water. This is readily available online and at all good fish and pet stores.

Seachem Prime and Tetra Aquasafe for Bettas are two good options for water conditioners.​

You should also own a tank thermometer. It is important for the water in your betta fish’s tank to remain at a specific and stable temperature so that your betta remains healthy.

This thermometer will be used to ensure the replacement water is at the same temperature as the tank when added.  

How do you change betta water?

These are steps for how to change the water in small home aquariums – i.e. without removing the betta fish. 

Step 1: You should first remove the tank cover and any large tank decorations. These are things like decorative rocks and houses. 

Step 2: Bring an empty bucket to the side of your tank and place one end of a siphon in the tank. If you do not have a siphon place one end of a hose into the tank.

The bucket should be lower than the tank so gravity can draw the water down the tube into your bucket.

Step 3: You will have to pull the water up by sucking the exposed end and dumping the water into the bucket before it enters your mouth. Depending on the siphon you have, there may be a bulb you can squeeze to get the water moving without sucking on the tube.

Step 4: Drag the end of the nozzle in the tank along the gravel at a 45-degree angle. This will agitate the rocks in the tank and help to release any decaying food collecting there.

Try not to remove too much water from the tank at any one time. This can stress your fish. Their unclean tank water is also a source of healthy bacteria for your fish and they need this to remain healthy. 

Step 5: Throw the excess dirty tank water down the toilet to dispose of it. 

Step 6: Fill a clean bucket with the correct amount of replacement water to fill the tank back up. Try to get the temperature to around 78 degrees Fahrenheit. 

Step 7: Add some water conditioner to the water to make it the correct chemical balance to keep your betta healthy. I’ll discuss adding water conditioner in the next section.

Follow the packet instructions for the quantity of conditioner to add and the specific instructions to follow. 

Step 8: Return any rocks or decorative housing to your betta tank. Gently pour in the replacement water once it is at the correct temperature.

Do this slowly so that you do not harm your betta fish. Alternatively, you could use the siphon to ensure it is added at a consistent flow. 

Step 9: If you have a filter in the tank, remove and clean or replace as necessary. Place the lid of the tank securely back on and plug in the filter. Turn on the heater and lights, and you’re all set. 

How Much Betta Water Conditioner Should You Use?

When You change your betta’s water, you’ll want to remove harmful chemicals like chlorine to make the new water safe for your betta. You can do this using a water conditioning product like Seachem Prime or Tetra’s Aquasafe.

Prime is generally though of as the better water conditioner, but it’s not practical to add to tanks smaller than 5 gallons. Aquasafe can easily be added to tanks of any size.

For some of these, depending on your tank size, you may want to use a pipette to add the conditioner, as it will speed things up.

Here is how much you should add for a few of the more common brands. Otherwise follow the directions on the back of the bottle.

Brand How Much Conditioner To Add
Seachem Prime 1ml per 10 Gallons
Tetra Aquasafe for Bettas
14 Drops or 1ml Per Gallon
Jungle Start Right 10 Drops per Gallon
.5ml per Gallon
Tetrafauna Aquasafe 1ml per Gallon

The brands that list drops per gallon are generally better for smaller tanks, as they usually have a nozzle that lets you add conditioner one drop at a time. The others usually just have open mouths that you have to pour out of.

Water conditioner generally is effective immediately, so you don’t have to wait for it to take effect.

When looking for something that treats water, you want to look for something that says it treats chlorine, chloramine, and ammonia. This will take the things that are most harmful to your fish out of the water.


Betta fish are the colorful floaty fish that you often see sold in small cups in pet stores.

Their scientific name is Betta splendens but they are also referred to as labyrinth fish and Siamese fighting fish.

The fish are native to the continent of Asia and live in shallow waters and slow-moving streams. Like humans, betta fish are diurnal, meaning they are awake in the day and asleep at night. 

They are often treated poorly in the animal trade supply chain and can be very traumatized because of this.

They have also been observed to suffer from depression and need a lot of mental stimulation in their environment. 

To keep your betta healthy and happy, you should always keep them in at least a 2 gallon tank and change 50% of the water once per week. In a 5-10 gallon tank, you can do a 25% water change once per week.