What is the optimal tank size for a Betta fish?

In this article, we will answer the question “What is the optimal tank size for a Betta fish?”. We will also discuss the factor we should consider when choosing a Betta fish tank, as well as the results of keeping a Betta fish in a small tank.

What is the optimal tank size for a Betta fish?

The ideal size is quite hard to tell, once the larger the tank, the better for the fish. Thus, it is better to talk about minimum tank size. Five gallon aquariums are the bare minimum for a Betta fish tank. 

Smaller tanks are typically more difficult to maintain than larger ones. This is because this type of tank can build up toxins and ammonia levels very quickly. Also, they can easily go through temperature and other parameter fluctuations. As a result, tiny tanks require extra water replacements than larger tanks.

Additionally to the minimum tank size for a Betta fish, it is important to consider space for plants and decorations that mimic the Betta fish natural environment and also other tank equipment, such as filter and heater.

Important tank characteristics to consider

The shape of your Betta fish tank 

Tall tanks are not recommended for Betta fish. They tend to swim horizontally in their native environment, which is shallow water. Betta fish are found in shallow water across the world. A tall tank will provide your Betta fish with less horizontal room to swim around. Thus, it is crucial to keep a Betta fish in a tank that is longer than tall.

What is inside the tank?

When choosing decorations and plants, it is fundamental to leave your Betta fish plenty of space to swim around. Additionally to the decorations and plants, it is necessary to reserve some space for equipment and other tank essentials, such as filter, heater, and substrate.

Some equipment is prepared for smaller tanks, and occupy less space, leaving more room for your Betta fish. Thus, if you are considering having lots of decorations and plants, opt for a bigger tank as your Betta fish will require some space to swim and explore.

Select an aquarium that has a secure cover

Betta fish are excellent jumpers, as seen by their size. Betta fish have a number of appealing characteristics, and this is one of them. In the wild, they can jump to grab food, escape from predators, or change to other ponds or water bodies. However, in a tank, the Betta fish could easily fall out of the water and die. It is crucial to have a well-placed lid to avoid any jumping accident with your Betta fish.

Bettas that require a bigger aquariums. 

The size of a giant Betta fish aquarium

The Giant Betta or King Betta is a Betta fish variety. As its name suggests, they are bigger than standard Betta fish. They can grow up to two times the size of a standard Betta fish. Because of their enormous size, they necessitate the use of bigger tanks. It is advised that you give these fish with a minimum of 10 liters of water. 

Betta sorority aquarium measurements

Differently from males, female Betta fish can live healthily in small groups of up to 5 individuals. This group of females is called a sorority. Betta fish sorority also requires more space, as it is usually composed of more than one female Betta fish. Thus a minimum tank size for a Betta fish sorority is 20 gallons. 

What if my tank is small for a Betta fish?

Smaller tanks are more difficult to keep than larger tanks. The case of a Betta fish tank is not different. As the fish will produce waste, it could easily make chemical levels higher and this could easily result in your Betta fish getting severe health issues. 

The ideal tank size will assist you in keeping these levels stable and avoid them building up. In addition to other tank care, it is also very important to perform water changes weekly.

Why do Betta fish from stores come in small cups and vases?

If you walk into a pet store, you will easily find out that Betta fish are kept in tiny recipients or cups. This is a huge issue, as it disseminates the myth that Betta fish can be kept in tiny tanks.

This occurs because Betta fish are cheap. Thus, some stores prefer providing them with only a tiny space instead of using an appropriate tank size and occupying the store with more expensive items,

Usually, Betta fish that are bought from tiny cups and recipients become more vibrant-coloured and grow larger when in an appropriate tank with at least 5-gallons of space.

Which tank size is optimal for Betta fish? 

Again, the larger the tank, the better for your fish. This rule is valid for every single fish species. Thus, it is better to talk about minimum tank size. Tanks with less than 5 gallons of water are severely discouraged and should be avoided while keeping Betta fish. 

When selecting an aquarium, there are several more factors to consider. These include: 

  • Larger aquariums are less difficult to maintain than smaller aquariums. Water changes and cleaning can occur weekly or biweekly in larger tanks, while tinier tanks will require these changes more frequently to avoid contaminants from building up;
  • It is a myth that Betta fish only requires 2.5 gallons of space to thrive in a tank;
  • Tanks with greater capacity are also more stable than tanks of lesser capacity. Temperatures and other water parameters fluctuate more smoothly than in smaller tanks. This stability will avoid your Betta fish from developing behavioural issues;
  • Betta fish require space to fully grow. Thus, having tiny tanks will not allow your Betta fish to completely and healthily grow to up to 3 inches;
  • There isn’t a tank large enough for a Betta fish in this establishment. If you opt for larger tanks, keep in mind they need to be longer than taller, as Betta fish prefer shallow waters, and also guarantee the tank is well-planted and prepared to house a Betta fish.


In this article, we answered the question “What is the optimal tank size for a Betta fish?”. We also discussed the factor we should consider when choosing a Betta fish tank, as well as the results of keeping a Betta fish in a small tank.

If you have any questions or concerns, please let us know in the comments section below!

Frequently Asked Questions (FAQs): What is the optimal tank size for a Betta fish?

What is the Betta fish natural environment?

Betta fish are original from tropical streams and shallow water bodies, such as marshlands and rice paddles from Southeast Asia. These environments are shallow and extremely vast. They also have lots of vegetation and slow-moving currents.

Do Betta fish tanks require a filtration system?

Yes, it is very important to keep a good filtration system in your Betta fish tank. This system will work on removing floating debris, preventing toxins and chemicals from building up, and aerating and oxygenating the tank water. 

Do Betta fish tanks require a heating system?

The presence of heating system may not be necessary in warm-weather places where it is not necessary. However, it is still recommended to avoid any water temperature fluctuation and fish stress. Betta fish are tropical fish, and as a result, they need warm water to survive. Betta fish thrive at temperatures ranging between 78 and 82 degrees Fahrenheit. For this reason, you may be required to have a heating system and a thermometer in your Betta fish tank.

What is the best substrate for a Betta fish tank, and how do I choose it? 

Sand or gravel are the most suitable substrates for Betta fish aquariums. They are usually very easy to keep and you can find them in several fish stores.

How big do Betta fish grow?

If a Betta fish have plenty of space and live in ideal conditions, it can grow up to 3 inches long. However, the average is around 2.25 inches long. Some breeders can select the Betta fish to grow up to 5 inches, but this is extremely uncommon.

How often should I run water changes in my Betta fish tank?

If you have a tank with at least 5 gallons of water, you can change 10 to 20% of the water every 7 to 10 days. Another option is to change 20 to 30% every 2 or 3 weeks. However, more frequent water changes are better to keep water parameters stable.


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