Our recommended tank size
The minimum tank size we recommend for a betta is 19 Litres / 5 US Gallons / 4 Imperial Gallons.
If you're a beginner to fish keeping our recommended betta tank size is 30 Litres / 8 US Gallons / 6.5 Imperial Gallons.
It's important to have a tank that at least meets this minimum, otherwise your betta will be unhappy, streseed and most likely become ill.
For more advice on keeping a healthy betta, see our page on how to care for a betta.
And to see some examples of tanks that are a suitable size, see our page on the best betta tanks.
What do other organisations say?
Practical Fishkeeping recommends 25 Litres (6.6 US Gallons).
The RSPCA recommends 15 Litres (4 US Gallons) as a minimum, or 20 Litres (5.3 US Gallons) as optimal.
In 2014 the Anabantoid Association of Great Britain (AAGB) released recommended betta keeping requirements stipulated 5 litres as a minimum, but especially for beginners, this is way too low in our opinion.
The Practial Fishkeeping article that shared the AAGB announcement had similar concerns.
Technically speaking, it is possible to keep a betta in smaller volumes than our recommendation, but it's not such a nice life for the betta.
The advantages of a larger tank
Apart from creating a nicer home for your betta to live in, there are other advantages to having an aquarium that goes above and beyond the minimum size.
Firstly, your betta is less likely to become sick, saving you the time, worry and cost of identifying and treating the illness.
Next, you'll need to do fewer water changes. As a rule of thumb, the larger your aquarium, the less frequently you need to do water changes.
Can a betta survive in a small tank?
Bettas have a reputation as being hardy fish, which means that many people mistakenly believe they are happy and healthy even in the smallest of containers.
This is simply not true. Bettas are intelligent fish — they need plenty of space and the right tank conditions to be stimulated, happy and healthy.
If you want to care for your betta properly, the best thing you can do is to upgrade its tank size, and learn about the other conditions needed to care for it properly.
A betta may survive for a short period in a small container, but it will not thrive.
Unfortunately there are plenty of photos of betta in decorative containers that are far too small, which creates the false impression that this is OK for a betta.
Similarly, people mistakenly believe a betta can be kept in a bowl. This is possible if the bowl is large enough, but still challenging for beginners.
What happens if you keep a betta in a tank that's too small?
If you keep a betta in a tank that's too small, not only will it be an unpleasant experience for your fish, but it will most likely lead to illness.
Not having enough space will make your betta stressed, which can then make it unwell.
And the smaller the capacity of your tank, the harder it is to maintain stable water conditions.
The vast majority of questions we get asked about betta fish that are sick stem from inadequate water conditions.
The smaller the capacity of your tank, the more the water parameters fluctuate.
The more water parameters fluctuate, the more stressful it is for your betta.
The more stressed your betta is, the more likely it will get sick.
Stores sell betta tanks / containers that are too small
Unfortunately, there are still many stores that sell containers for bettas that are simply too small.
In the photo below, you can see display bettas for sale. They are in small, temporary containers.
On the shelf below, you can see a "Betta Keeper" container. This is not a suitable long term home for a betta.
Sometimes bettas will be housed in a small container on a temporary basis for isolation or transportation purposes, so in a way there is some logic to offering these small containers for sale (although there are plenty of household items that would also suffice on a temporary basis).
But the container shown in the photo above is not being presented in this light. It states on the box ‘the perfect intro to betta keeping’ and ‘ideal for home and office’, which it certainly isn’t.
Presenting a product like this for sale in a fashion that doesn’t make it clear that it’s not suitable betta housing is irresponsible.
The above photo was taken at a well-know large chain pet store. Stores such as this are seen as an authority figure by customers.
People have a responsibility to do their own research before buying a product, but by offering such products for sale the store appears as if it is endorsing them. People will see the product and believe it’s suitable.
A visual illustration
This graphic is drawn to scale and shows the Petco container size compared to our recommended size:
As you can see it is tiny in comparison.
The container in the photo above is a quarter of a US gallon. Our recommendation is 5 US Gallons. That makes it 1 / 20 of our recommended size.
Even if you were to half our recommendation, the pictured container would be 1 / 10 of the size.
What if you've bought a home for your betta not realising it's too small?
This is an easy mistake to make as a beginner so don't be too hard on yourself.
The most important thing to do is to rectify the situation as quickly as possible.
See our post on setting up a betta tank for more advice.