Akar

Betta akarensis is a paternal mouthbrooding labyrinth fish from Borneo, collected in Brunei and the Malaysian state of Sarawak. It lends its name to the Betta akarensis group of closely related species and is considered one of the more widely distributed Bornean Betta. Most are collected from blackwater, though it also lives in clear flowing streams, roadside ditches and larger ponds.

Homalopteroides weberi is a hillstream loach from Sarawak in Malaysian Borneo, described from the Akar River and possibly endemic to the state. Poorly known in the aquarium hobby, it was questioned as a possible synonym of Balitoropsis stephensoni by Kottelat (2012), but Randall and Page consider it distinct. It inhabits swiftly-flowing streams and headwaters with clear, oxygen-saturated water.