Betta fish are known for their brilliant colors and long fins, but they did not always look this way. In nature, betta fish look more grayish green or brown. The artificially selected colors catch your eye while they sit on the shelf of commercial and local pet stores. But have you ever wondered why they have to be in individual containers? As it turns out, they can be aggressive towards each other as well as other colorful fish. Knowing why do betta fish fight can help you better understand your colorful pet.


So, why do Betta fish fight? Back when they were first named Siamese fighting fish, these beauties were pitted against each other for entertainment. The colors, patterns, and long fins we see nowadays in commercialized betta fish were established through careful selective breeding, but what most people don't know is that breeders wanted betta fish to be aggressive towards other betta fishes long before they wanted the pretty, flashy ones. Nowadays, this is illegal, but it changed the breeds of betta fish commonly found on the market today.

 Why Do Betta Fish Fight?

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It is easier to understand the behavior of an animal once its history and natural environment is understood. Understanding where the betta comes from will help you understand why do betta fish fight.


What Is a Betta Fish?

Known in the aquarium trade as betta fish, the scientific name for these eye-catching fishes is actually betta splendens. The commonly used name actually refers to the genus of which the species belongs to.

A Brief History of the Siamese Fight Fish

Bettas fish became popular some time during the early 1800s in what was then Siam (now Thailand). Locals, especially children, would catch the fish in the shallow waters of the rice paddies and wager on which fish would win. The battle would be over when a fish would quit and swim away. The fight was judged by the bravery of the fish and not the amount of damage inflicted. The winners were bred and sold. No one questioned why do betta fish fight.


In 1840 the King of Siam gave some of these fish to a Danish zoologist, Theodor Cantor, who studied them. Eventually, the fish became popular in France and Germany and the betta fish eventually was brought to San Francisco, CA in 1910.


From Siamese Fighting Fish to Betta Fish

During the 1800s, these fish were known as the Siamese Fighting Fish because of their aggressive behavior and how they were used to entertain. In fact, they were such a popular form of entertainment that the King of Siam started a registry and even taxed betta fish owners.

The first time these beauties were named, the identifying zoologist, Theodor Cantor, chose a scientific name that was already taken. Charles Tate Regan renamed them bettas splendens or “beautiful warrior.” When spoken in English, most Americans mispronounce the name. Confused with the second letter of the Greek alphabet, the name is actually pronounced “bet-tah.” In Thailand, they are called “plakat”, meaning biting fish.


Origins of Aggression

So why do betta fish fight? Bettas are part of the gourami family and are known to be very territorial, especially the males. If housed in the same fish tank with not enough space (most commercial fish tanks don't have enough space) these fish will attack each other, sometimes maiming each other, until one of them backs off or swims away.

While it is widely believed that bettas are warriors that fight to the death, this is a very common misconception. These fish are merely territorial and want the other fish out of what they consider to be their space. They do not go out of their way to kill each other; they are just threatened by the presence of each other. Usually, it is a bacteria infection that kills the injured fish.


Unique Features: The Labyrinth Organ

Southeastern Asia is known for extreme flooding from storms during the rainy seasons followed by severe droughts during the warm seasons. These fish would find themselves in shallow, muddy waters competing for resources like food, shelter, and oxygen. To be able to endure stagnant, oxygen-deficient water, bettas developed a labyrinth organ. This allows the fish to breathe out of water, but they still have to stay wet to survive.


How Do Betta Fish Mate If They Fight?

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Usually, males are more aggressive than female betta fish. This is due to the fact that the male bettas protect the nest. They even chase the mother away to keep her from eating the fertilized eggs.


It is not recommended to keep male and female bettas in the same tank except temporarily for breeding. This task should only be taken on by experienced bettas owners and knowledgeable fish breeders as there are instances where, instead of courting, male and female bettas will attack each other.

Betta Breeding

As mentioned earlier, betta fish in the wild are usually brown, grey, or green in color and only display their flashy colors as a sign of aggression or courtship. Thanks to both European and American breeders, today betta fish are available in a wide range of colors, patterns, and fin types can be found.



So How Do Betta Fish Mate?

When a male is interested in a female betta, he will spread his fins, flare his gills, and do a twisting-type dance. If the female is also interested, she will display darker colors as well as vertical lines referred to as breeding bars. Males may also display breeding bars, but not always due to their vibrant colors.


A male betta fish take on the task of building the nest long before he meets his female mate, even in captivity. The male even goes on to raise the young until they are old enough to go out on their own. To build bubble nests, they suck air from the surface and use their mucus to form air bubbles for the eggs to sit on. If they fall through the nest, the father betta fish works hard to put them back in the nest and repair any damage.


The spawning process for bettas is known as a “nuptial embrace,” since the male wraps his wraps his body around the female fish. This behavior helps release anywhere from ten to forty eggs (or until the female is exhausted off eggs).


Fertilization takes place externally once the male betta releases milt around the eggs. Usually after all this the male has to chase away the mother from his territory. There have been instances of the mother helping the father to care for and raise the young, but more often than not she will try to eat all the eggs she can. In captivity, if the female is not removed the male will most likely kill her.


The eggs only need one or two days before they hatch into larvae, but they stay in the bubble nest until their yolk in absorbed. Then the fry (freshly hatched fish) start their free-swimming stage of life.


Caring for Betta Fish

Unfortunately, because people see these pretty fish is small containers at the pet store, they think they can thrive in containers like small fish bowls or flower vases, but that is not the case. In the wild a single betta fish can guard up to 3 cubic feet.


Aquarium Space & Filtration

While it is recommended to give a single betta fish at least two gallons of water, they really prefer a lot more space. Ideally, if you're shopping for a tank, consider buying a bigger ten gallon one. Trying to save a few bucks will not be doing your fish any favors. The smaller the tank, the more often it will need to be cleaned. Using a larger tank and a filtration system is recommended but not required.


When changing the water, you might think exchanging 90 percent of the tank with fresh water would be best, but fish work hard to acclimate to the water in the tank and too much change too quickly can cause them to go into shock. Instead, only remove 20 to 30 percent at a time.

​Nesting Behavior

Although some betta fish breeders do manage to get females with fairly long fins and bright colors. typically what you find in the store are male fish, since female bettas almost never develop fins as showy as males of the same type and are not as vibrant in color. These male fish will make a bubble nest even if a female is not present. Often these bubble nests are constructed around plants and rocks that break the surface of the water are often used as the “base” of these nests. So they prefer plants that break the surface but do not crowd the surface of the water.


High Aggression Also Means Highly Invasive

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As a highly aggressive species, these fish are known to attack almost any fish, especially anything prettier, slower and/or smaller than it. Male bettas have shown signs of aggression towards their own reflection. Some betta fish will even show signs of stress if they can see their reflection for an extended period. And because of their dark history, in captivity a fight can last entire minutes whereas, in the wild, a fight would only last a few moments.


In captivity, observed signs of aggression include flaring gills covers and fins to appear more intimidating, which both genders will do if they feel threatened by someone or something or are courting each other. If severely stressed or frightened, both genders will also display horizontal bars, but they are harder to see in color-intense adult males.


In January 2014, a large population of betta fish were discovered in parts of Australia along the Adelaide River Floodplain. They are known to threaten not only fish, but also frogs and other wetland wildlife. Always dispose of your betta fish properly. If you can't keep your fish, send it back to a pet store rather than throw it into a body of water!