Monopterus

The swamp eel, Monopterus albus, is very widespread, found from India and China to Japan, Indonesia, the Philippines and Australia. Not a true eel, it has a single gill slit and an accessory breathing organ, and during dry spells it burrows into wet earth. Growing to around 100 cm, nocturnal and piscivorous, it is best kept singly, and the tank must have an extremely tightly-fitting, heavy cover.