Knifefish are some of the most interesting freshwater aquarium fish available. Their unique “knife blade” body shape and ability to swim backwards using their undulating bottom fin make them fascinating additions to appropriate aquarium communities. Knifefish can be placed in two main groups: The largest group belongs to the Order Gymnotiformes and are found in Central and South America. They include ghost knives, banded knives and glass knives. A smaller group, in the Family Notopteridae, are native to Southeast Asia and Africa and include featherfin, African and clown knives. Most knifefish have the ability to generate and receive electrical discharges, which they use for navigation, locating prey and communication. Knifefish are not for beginning aquarists due to their specialized feeding requirements and, in some cases, large adult size.