Mahaweli basin

The Ceylonese combtail, Belontia signata, is a labyrinth fish endemic to the central and southern river systems of Sri Lanka. Also referred to as the 'Ceylon fighting fish', it differs from B. hasselti in its reddish body and the absence of mosaic patterning in the unpaired fins. At least three putative phenotypes have been recorded, one described as the questionably valid subspecies B. s. jonklaasi. It is not recommended for the average community aquarium.

Pethia reval is a small cyprinid endemic to western Sri Lanka, known from the Kelani and Maha Oya river systems and the drainages between them. Considered a red-finned colour form of P. cumingii before its description, it is a smaller fish, to 33.6 mm SL, with red dorsal, anal and pelvic fins (pale yellow in the Kalu River population). The Mahaweli River population appears to have been introduced.