The eel-tailed catfish, also known as the freshwater catfish, Tandanus tandanus, is a species of catfish (order Siluriformes) of the family Plotosidae. The species is endemic to Australia and occurs throughout most of the Murray-Darling River drainage and in coastal drainages from northern Queensland to central New South Wales. It is brown to olive green, reddish or even purplish above, and pale below (Australian.Museum).