Gymnotidae
From The Aquarium Wiki
Gymnotidae, or Naked-Back Knifefish, belong to the order Gymnotiformes. They are a group of Knifefish that are found only in fresh waters of Central America and South America. All have organs adapted to the exploitation of bioelectricity. The family has 33 valid species in two genera. There are a number of undescribed species known in museum collections.
