Betta or Siamese Fighting Fish

Betta splendens

Bettas, also known as Siamese fighting fish, are small (up to 3 inches long) rather plain-colored fish native to the Mekong River basin in Thailand and Cambodia. They feature a unique organ (the labyrinth) that enables them to breathe atmospheric oxygen and thus to live in very low-oxygen waters such as slow streams, paddies, and ditches. The name “fighting fish” refers to the aggressive behavior of territorial males.

After more than a century of captive breeding, bettas in the pet trade are very different than their wild ancestors. Bred for beauty, pet bettas come in a variety of bright colors and have long flowing fins (longer in males).

Did You Know?




Little Cause for Concern

Bettas are almost exclusively bred in captivity, and therefore the pet trade does not pose a threat to wild populations. However, wild populations may be declining due to habitat loss, so it is important to only purchase captive-bred bettas.

EcoHealthy Recommendation:


Invasion Threat


Some Cause for Concern

There is at least one record of a breeding population of bettas becoming established in the wild in Florida for a few years only. There are some established non-native populations in other more tropical areas of the world. Although possible in tropical environments, there is probably little risk for permanent invasive populations to occur in most areas of the United States.

EcoHealthy Recommendation:


Ease of Care


Little Cause for Concern


Bettas are relatively easy to breed and keep in captivity. They do well even in small aquaria. Males are aggressive and should not be kept with other fish.  Bettas also need warm (78º–80°F), still water (fins can be damaged by vigorous currents). They are very sensitive to chlorine, so tap water should be treated with a chlorine and chloramine remover (available at pet shops) prior to use. Take care not to overfeed because uneaten food can rapidly foul the water.

EcoHealthy Recommendation:

Before acquiring a betta, be sure to research its specific care requirements. For example, bettas typically require freeze-dried tubifex worms. Although bettas are commonly sold in small bowls, PetWatch recommends keeping bettas in larger aquariums with live vegetation that reaches the surface to simulate their natural environment.

Health Threat


Some Cause for Concern

Bettas may carry nematode parasites and certain bacteria (Mycobacteria species) that can cause disease in fish and infrequently skin infections in humans. Even healthy-looking fish may be infected by these bacteria. People with compromised immune systems are more susceptible to these skin infections, commonly called “fish-handler’s disease.” Bettas can also carry Edwardsiella bacteria which can infect commercially important farmed fish such as catfish, salmon, trout, and tilapia.

EcoHealthy Recommendation:

Due to the potential for disease transmission to humans and other household pets, always wash your hands after handling a fish or touching the aquarium water. When purchasing a pet fish ask the seller if the fish or group of fish has a history of any health problems and for a list of any medical treatments the animal or tank has received.

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