The name spiny eel is used to describe members of two different families of fish: the freshwater Mastacembelidae of Asia and Africa, and the marine (and generally deep sea) Notacanthidae.
These two families are not related: the Notacanthiformes belong to the Superorder Elopomorpha, whose members are characterized by having leptocephalus larvae.
The freshwater Mastacembelids do not share this characteristic and are popular specimens in the aquarium trade.
Spiny Eels from Sri Lanka, China, Southeast Asia and India are also from two genera: Macrognathus and Mastacembelus.
The most commonly found Spiny eels in the Aquarium trade are the Macrognathus and Mastacembelus from Sri Lanka, China, Southeast Asia and India.