Perak

Barbonymus gonionotus is a large cyprinid with an enormous distribution across Southeast Asia, from the Mekong to Java and Sumatra. It inhabits larger, slow-moving rivers and their floodplains, moving into flooded forest to feed and spawn, and is increasingly found in man-made canals and lakes. Plain grey caudal and dorsal fins and pale yellow pelvic and anal fins separate it from congeners. Populations in Peninsular Malaysia appear to be introduced.

Betta pugnax is a paternal mouthbrooding labyrinth fish from much of Peninsular Malaysia and Singapore, described from Penang. It lends its name to the B. pugnax complex. Populations inhabit shallow, flowing clear-water hill streams as well as stiller forest swamps. It is not among the more aggressive members of the genus and can be maintained in a pair or group.

The silver tiger perch, Datnioides polota, is a tiger perch widely distributed in southeastern Asia, from India and Bangladesh east to Indonesia. Mostly found in brackish habitats such as estuaries, mangroves and coastal lagoons, it has a highly variable colour pattern with up to 7 dark bars. The name D. quadrifasciatus is sometimes applied to it, but that name is a junior homonym and polota takes precedence.

Homaloptera parclitella is a 'lizard' loach from Peninsular Malaysia and the Sai Buri, Bang Nara and Kolok river systems of southern Thailand. It was previously considered a form of H. orthogoniata and may be seen identified as such online and in print. It always has two large, saddle-shaped markings on the back, where H. orthogoniata has three, and it lives in swift, clear, oxygen-saturated streams.

Rasbora tornieri is a cyprinid from Sumatra, Borneo, Peninsular Malaysia and the Mekong drainage in Cambodia. Its identity was unclear for decades before its redescription by Ng and Kottelat (2013). It is very similar to R. dusonensis, which shares the Musi river with it, but its caudal fin is carmine red, against bright yellow in R. dusonensis. It lives in flowing streams and peat swamp blackwaters alike.

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.

The Indonesian tiger perch, Datnioides microlepis, is a large tiger perch from Peninsular Malaysia, Sumatra and Indonesian Borneo. It has 6 to 7 wide dark bars and small body scales, lives only in large, deep lowland rivers, and grows to 500 mm SL. Juveniles may form groups, but adults are not gregarious and respond aggressively to conspecifics and similarly-shaped fishes.

The bronze featherback, Notopterus notopterus, is an air-breathing notopterid from the Indian subcontinent and Southeast Asia. Also called 'Asian knifefish' or 'ghost knifefish' in the trade, it grows to 600 mm and arguably has no place in the ornamental hobby given its adult size and specialised requirements. The single species in Notopterus is likely to represent a complex of closely-related species.