How Big Do Betta Fish Get?

Written by Brandi Allred
Updated: January 24, 2023
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They may be the most popular aquarium fish in the world, but just how big do betta fish get? Unlike many other brightly colored fish, bettas live in fresh, not salt, water. Their name is often pronounced ‘BEY-ta’, but the correct pronunciation is actually closer to ‘BET-ah’. Their name comes from the Malay word for a group of warlike people. Like their namesake, betta fish are very aggressive, and often can’t be kept with other bettas. 

Although there are over 70 species in the betta genus, only two are bred for commercial purposes. The most common, and most averagely sized betta species, is Betta splendens. One more species, betta anabantoids, grows even larger than the regular betta; it’s known as the giant betta.

Here, we’ll learn more about the origins of betta fish, and why they’ve become such popular pets for aquarium enthusiasts around the world. We’ll examine the life cycle of the betta, and just how big they are at each stage of development. Then, we’ll take a look at the average size of an adult betta, and compare this to the size of the giant betta. Next, we’ll summarize the things you need to ensure your betta grows to its full potential. Finally, we’ll review whether or not a betta fish might make a good pet for you.

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Where Do Betta Fish Come From?

Betta fish, also known as Siamese fighting fish, are bred and exported almost exclusively from Thailand; they’re native to the shallow waters of Southeast Asia. Genetic research shows that they’ve likely been domesticated for over 1,000 years, longer than any other species of fish. 

Throughout the centuries, betta fish have been selectively bred both for their distinctive coloring, and for their aggressiveness. Historically, they were important for gamblers, who would pit males against each other, betting on the winners. Male betta fish are particularly aggressive and will try to chase away any other frilled fish in the same tank. 

Today, bettas can be found in just about every pet store—they can even be purchased on the internet. Captive specimens have far showier fins in a larger variety of colors than their wild brethren.


betta fish

grow up to three inches long

©Arif Supriyadi/

How Big are Baby Betta Fish?

Like many fish, bettas are born to eggs. These eggs are kept safe in a bubble nest created by the father. Incubation takes only 24-36 hours; the fry (baby fish) emerge from the nest only a couple of days after hatching. At the time of hatching, they measure under ¼ inch in length, but grow rapidly. By the time they’re 4-5 months old, betta babies are considered mature and fully grown.

Once the mother betta fish lays her eggs for the male to fertilize, it’s important to separate her from them. Female bettas, especially those that have just spawned, are prone to eating the eggs. Male bettas, however, will actually pick up any stray eggs, and place them safely inside the bubble nest.

How Big are Adult Betta Fish?

Adult betta fish are between 2-3 inches long, with 2.5 inches being average. They attain this length by the time they’re six months old. Unlike other fish, like goldfish, bettas don’t continuously grow throughout their lives. Once they reach around three inches, they grow no more. This cap on size, coupled with their ease of care, makes them the ideal pet fish for starter aquarium enthusiasts.

Betta vs Giant Betta: Size Comparison

Almost all betta fish you see in the pet store are the same species—Betta splendens. But, there’s one more species of betta—Betta anabantoides—available to enthusiasts. This species is known as the giant betta, and the name is well deserved.

While regular betta fish top out at three inches, giant betta fish can grow up to seven inches. Not only are they a separate species; they’ve actually been selectively bred to be bigger. Giant bettas not only need more food than other bettas, they also need a larger aquarium. Despite the bigger body, giant betta fish live just as long as normal bettas. Lifespans for both range from 2-5 years on average, though some well taken care of betta fish have lived as long as ten years.

Betta fish, Siamese fighting fish with green plants

Betta fish are popular, easy to take care of, aquarium fish

©subin pumsom/

How to Ensure Your Betta Grows to Maximum Size

Buying a betta fish is no small decision; once you take that fish home, you are solely responsible for its health, safety, and longevity. The best way to ensure that your new betta has everything it needs to grow to full size, and live a long, happy life, is to purchase an appropriately sized tank and water filtration system.

A single betta fish should have a five-gallon aquarium filled with neutral pH water between 75-82 degrees Fahrenheit. Bettas are naturally curious and intelligent, and require stimulation. This can be provided with either real or artificial aquatic plants and places to hide like ornaments, caves, or driftwood. 

Betta fish are prone to overeating; any food left uneaten after five minutes should be removed from the aquarium. They only need to be fed once per day; they’re carnivores, and most of their diet should consist of animal protein. This can be provided through flakes, pellets, brine shrimp, or bloodworms.

Are Betta Fish Good Pets?

Betta fish are popular for a reason—they’re fun to look at, and easy to take care of. A well-cared for betta should reach at least 2.5 inches in length, and may live for over five years. Giant betta fish get even bigger—up to seven inches. If you’re thinking about adding a betta to your family, anticipate providing them with a five-gallon tank, and plenty of stimulation, and you and your new fishy friend should get along just fine.

The photo featured at the top of this post is © ANURAK PONGPATIMET/

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About the Author

Brandi is a professional writer by day and a fiction writer by night. Her nonfiction work focuses on animals, nature, and conservation. She holds degrees in English and Anthropology, and spends her free time writing horror, scifi, and fantasy stories.

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