Chi

The emerald betta, Betta smaragdina, is a bubble-nesting labyrinth fish from the Khorat Plateau in eastern Thailand and Mekong tributaries in Laos. It inhabits still and sluggish waters such as rice paddies, swamps and roadside ditches. It has been line-bred for aggression in eastern Thailand, and selectively bred and hybridised for the ornamental trade into colour forms that do not occur naturally. Wild populations vary in the extent of red or green patterning and are often labelled by locality.

The sparkling gourami, Trichopsis pumila, is a small labyrinth fish from the lower Mekong basin and central and southern Thailand. Also known as the pygmy gourami, it has a solid dark midlateral stripe topped by a row of dark blotches, which with its small size separates it from T. schalleri. Both sexes produce audible 'croaking' sounds with a specialised pectoral mechanism, and most traded fish are produced commercially.

Trichopsis schalleri is a croaking gourami from the lower Mekong basin and the Chao Phraya watershed in Thailand, Laos, Cambodia and Vietnam. Sometimes called the Mekong croaking gourami or three-stripe gourami, it is larger than the similar T. pumila, and its upper body stripe varies with mood and sometimes fades entirely. Peaceful unless breeding, it can be kept in a pair or a group.

The giant snakehead, Channa micropeltes, is a predatory fish from Southeast Asia that grows to well over a metre. Juveniles are sold as 'red' or 'redline' snakehead, but it is suitable only for public installations or the very largest private aquaria. Unlike most Channa species it is pelagic and needs plenty of room to swim, and adults become aggressive at sexual maturity.

Mystacoleucus chilopterus is a pelagic cyprinid from the middle Mekong, Chao Phraya and Mae Klong basins in Laos and Thailand. It favours flowing lowland rivers and swiftly-flowing forest streams with rock and gravel. The anal fin has a concave margin and the dorsal and caudal fins black margins, and like all Mystacoleucus it has a forward-pointing predorsal spine that can become entangled in an aquarium net.

Mystacoleucus ectypus is a pelagic cyprinid from the middle Mekong basin in Laos and Thailand, and may be endemic to the Khorat Plateau. It inhabits flowing lowland rivers and swift tributary streams with rock and gravel. It has a triangular blotch at the tip of the dorsal fin but no black fin margins or crescent-shaped scale markings, and like all Mystacoleucus it has a forward-pointing predorsal spine that can snag in a net.