Every species

Betta gladiator is a large paternal mouthbrooding labyrinth fish presumed endemic to the isolated Maliau basin in Sabah, Malaysian Borneo. A member of the B. unimaculata complex, it grows to 90 mm SL. The type series came from heath forest with acidic water of pH 4.2-4.8, where adults were spaced around a metre apart and usually accompanied by a few juveniles. It has a reputation for aggression.

Betta hendra is a small bubble-nesting labyrinth fish known only from the Sabangau peat swamp forest near Palangkaraya, Central Kalimantan, Borneo. A member of the B. coccina group, it has bright iridescent green flanks and fins where most of its relatives are red. It has been traded as B. sp. 'Sengalang/Palangkayara' and B. sp. 'Sebangua'. The type locality is still, shaded blackwater with a pH around 4.0.

Betta hipposideros is a paternal mouthbrooding labyrinth fish from peat swamps in western Peninsular Malaysia and eastern Sumatra, Indonesia. A member of the B. waseri group, it is most easily told from its relatives by a black horse-shoe shaped marking on the throat. An obligate inhabitant of peat swamps and blackwater streams, where the pH can be as low as 3.0 or 4.0, it may have to survive for several weeks in moist leaf litter at certain times of year.

Betta ibanorum is a paternal mouthbrooding labyrinth fish from southern and western Sarawak, Borneo, where it exists in several colour forms. Most known localities are blackwater peat swamps, but it has also been collected from clear streams, roadside ditches and a pool at the top of a waterfall. A member of the B. akarensis group, it is uncommon in the hobby and apparently more often fished for food.

Betta ideii is a large paternal mouthbrooding labyrinth fish from southern South Kalimantan and Pulau Laut, Indonesian Borneo. Traded as B. sp. 'Laut' before its description, it belongs to the B. unimaculata complex and grows to 110 mm SL. It looks very similar to its closest relative B. patoti but lacks dark vertical bars on the flanks, and adult males are much darker.

The crescent betta, Betta imbellis, is a labyrinth fish thought to be native to southern Thailand, Peninsular Malaysia and northern Sumatra. It has been line-bred for aggression in southern Thailand and hybridised with B. splendens and other congeners for the ornamental trade, producing colour forms that do not occur naturally. Introduced ornamental forms and other Betta spp. are having an adverse effect on the genetic integrity of some wild populations.

Betta krataios is a paternal mouthbrooding labyrinth fish that appears endemic to the lower River Kapuas basin in West Kalimantan, Indonesian Borneo. Traded as B. sp. 'Kapuas' before its description, it is sometimes confused with B. dimidiata, the other member of the B. dimidiata group. The two are easily told apart since the caudal fin is rounded in B. krataios and spade-shaped and more extended in B. dimidiata.

Betta kuehnei is a paternal mouthbrooding labyrinth fish from Kelantan state, northeastern Peninsular Malaysia, and neighbouring Narathiwat, Thailand. A member of the B. pugnax complex, it has a rounded caudal fin in both sexes and adult males carry intense blue or bluish-green iridescence on the head and throat. It may be conspecific with B. sp. 'Satun'. The type locality is a shady, clear forest stream with beds of Cryptocoryne cordata.

Betta lehi is a paternal mouthbrooding labyrinth fish endemic to Borneo, in southwestern Sarawak and the lower River Kapuas basin in West Kalimantan. A member of the B. pugnax complex, it has green iridescent scales on the opercle and body and a light blue iridescent band on the anal fin. It inhabits forest peat swamps, acidic clearwater swamps and associated streams, where the pH can be between 3.0 and 5.5.

Betta livida is a small bubble-nesting labyrinth fish endemic to peat swamps in northern Selangor state, Peninsular Malaysia. A red member of the B. coccina group, it has a small iridescent green lateral blotch that fades with age. Much of its range has been turned over to oil palm or rubber plantations, and it is listed as endangered by the IUCN, so captive reproduction should be the priority for anyone keeping it.

The Brunei beauty, Betta macrostoma, is a large paternal mouthbrooding labyrinth fish endemic to Brunei and the northern tip of Sarawak, Borneo. It grows to 100 mm SL, and males are red with a red patch on the opercle and an ocellus in the dorsal fin. It lives in still, shady pools at the top of rainforest waterfalls. Listed as Vulnerable by the IUCN, it has been banned from export by the Sultan of Brunei.

Betta mahachaiensis is a bubble-nesting labyrinth fish known only from a handful of coastal localities around Bangkok in central Thailand. The only member of the genus to occur exclusively in brackish water, it inhabits tidal coastal swamps and builds its nests among nipa palms. Once considered a hybrid, it has been confirmed as a distinct species, and most of its habitats are under extreme threat from the expansion of Bangkok.

Betta mandor is a paternal mouthbrooding labyrinth fish from near Mandor and Anjungan in the lower Kapuas basin, West Kalimantan, Borneo. Known as B. sp. 'Mandor' or B. sp. 'ninja' before its description, it belongs to the B. foerschi group. Males are black and females brown, with twin red bars on the opercle. It is sometimes traded as B. foerschi, and the two can be difficult to tell apart.

Betta midas is a stout-bodied labyrinth fish from the lower Kapuas basin in West Kalimantan, Indonesian Borneo, and may also occur in western Sarawak. It has been traded as B. anabatoides in the past, and most images of it are labelled as such. It has gold iridescent scales on the opercle, belly and body. The paratype series came from a blackwater river in peat swamp forest with a pH of 4.1.

Betta miniopinna is a small bubble-nesting labyrinth fish endemic to Bintan Island, Indonesia, where it is known from a few northern localities. A dark member of the mostly red B. coccina group, it is most similar to B. persephone. Development for tourism and rubber plantations has left it restricted to a few pockets of primary peat swamp forest, and it has been listed as Critically Endangered on the IUCN Red List since 1996.

Betta ocellata is a large paternal mouthbrooding labyrinth fish from Sabah, northeastern Borneo, and the Sebuku River basin in East Kalimantan. A member of the B. unimaculata complex, it grows to 90 mm SL and has a pointed, slightly conical head. It has been collected from clear flowing streams, elevated headwater pools, turbid forest streams, ox-bow lakes and ponds in oil palm plantations.

Betta pallida is a small paternal mouthbrooding labyrinth fish described from Narathiwat province at the southern tip of Peninsular Thailand. Known as B. sp. 'southern Thailand' before its description, it belongs to the B. picta group and has a yellowish head and body with three lateral stripes. It has been collected from a shallow, slow-moving creek with clear, slightly tannin-stained water over leaf litter.

Betta pallifina is a large paternal mouthbrooding labyrinth fish from a remote part of the upper Barito basin in Central Kalimantan, Borneo. A member of the B. unimaculata complex, it grows to 90 mm SL, and females have an orange band in the anal fin. It inhabits forested headwater streams with clear, flowing water, dense marginal plants and a pH of 6.6-7.4.

Betta pardalotos is a large paternal mouthbrooding labyrinth fish from the Musi drainage near Palembang, South Sumatra, Indonesia. A member of the B. waseri group, it is best told from its relatives by the throat, which has two white, roundish patches on a black background. It is possibly endemic to the lower Musi basin, and the type series came from small freshwater channels draining into the river.

Betta patoti is a large paternal mouthbrooding labyrinth fish from East Kalimantan, Borneo, described from the Mangar River near Balikpapan. A member of the B. unimaculata complex, it grows to 100 mm SL and has 10-14 dark vertical bars on the lower body. Colour varies with locality, from blackish-barred fish around Balikpapan to more reddish ones further north.