Betta is a large genus of small, often colorful, freshwater ray-finned fishes in the gourami family (Osphronemidae). There are 28 known species of betta. The type species is B. picta, the spotted betta. By far the best known Betta species, however, is B. splendens, the Siamese fighting fish.
Bettas are anabantoids, which means they can breathe atmospheric air thanks to a unique organ called the labyrinth. This accounts for their ability to thrive in low-oxygen water conditions that would kill most other fish, such as rice paddies, slow-moving streams, drainage ditches, and large puddles.
The various bettas can be divided into two groups, based on their spawning behaviour: some build bubble nests, like B. splendens, while others are mouthbrooders, like B. picta. The mouthbrooding species are sometimes called "pseudo bettas", and are sometimes speculated to have evolved from the nest-builders in an adaptation to their fast-moving stream habitats.
Betta pellets are small, round edible pellets that are food for most betta species. Betta pellets are made out of crude protein, crude fat, crude fiber, crude ash, moisture, phosphorus, certain vitamins, and other ingredients.
There is often much confusion in terminology regarding these fish. So-called "Siamese fighting fish", B. splendens, are frequently sold in the United States simply as "bettas." Fish fanciers are thus often unaware that, as of 2006, there are around 65 species classified within the genus Betta. A further source of confusion is that while the generic name Betta is italicized and capitalized, when used as a common name it is usually not capitalized. The common name of Betta pugnax, for example, is thus Penang betta.
The name Betta (or betta) is .That is, the first part is the same as the English word bet. By confusion with the name of the Greek letter beta, the name is often pronounced /ˈbeɪtə/ in American English, and may be misspelled with one t. The name of the genus is unrelated to that of the Greek letter, being derived from ikan bettah, in a local language in Thailand.
While many Betta species are common and B. splendens is ubiquitous in the aquarium trade, other bettas are threatened. The IUCN Red List classifies several Betta species as Vulnerable. In addition, B. livida is Endangered, and B. miniopinna, B. persephone, and B. spilotogena are Critically Endangered.
The United Nations Environment Programme lists an unconfirmed species, Betta cf. tomi, as having become extinct in Singapore between 1970 and 1994. This likely refers to the extirpated Singaporean population of B. tomi, which continues to exist in the wild in Indonesia and Malaysia as well as in captivity; the Red List classifies it as Vulnerable.
The currently described Betta species can be grouped into "complexes" for conservation purposes. (This grouping of species makes no claim at representing a taxonomic reality.) The complexes of the associated species are: