This species is widely-distributed in the Mekong river system in Thailand, Laos, and Vietnam, Salween and Ayeyarwaddy rivers in southern China, Myanmar, and Thailand, plus various smaller basins in Vietnam and China. It has also been recorded from the islands of Hainan and Hong Kong.

Type locality is given as ‘China: sent from Hong Kong’.

Known from the from the Red River in northern Vietnam and Yunnan province, southern China, plus the Thái Bình, Sông Kỳ Cùng, Mã and Lam rivers in Vietnam and possibly the Nam Xam and Nam Ma drainages in Laos.

Type locality is ‘Market in Hanoi, Vietnam’.

M. opercularis is a classic aquarium fish, having been introduced to the hobby by a French soldier named Gerault in 1869. Of the initial 100 specimens shipped, 22 survived and were successfully bred later that same year by another Frenchman, the Parisian Pierre Carbonnier. This gives the species the distinction of being one of the very first ornamental fish imported to Europe. It is also known as ‘Chinese fighting fish’, ‘paradise gourami’, and ‘blue paradise fish’.