The clown featherback, clown knife fish, or spotted knife fish, Chitala ornata, is a nocturnal tropical fish with a long, knife-like body. and The royal knife fish or Indochina featherback, Chitala blanci, is a species of fish in the Notopteridae family found in the Mekong basin in Cambodia, Laos, Thailand, and Vietnam. Adult size about 10 to 40 inches (25- 50 cm) maximum 100cm
The knife fish is very unique, with normally silvery gray with a long knife-like body (laterally compressed) and a long anal fin that gives these fish their regular name. The Mature clown knife fish normally have five to ten (or more) black spots ringed with white colored that always decrease in size as the fish grows. These ocellated spots and the lack of faint stripes on the back separate it from Chitala chitala. Juveniles lack the spots but are overall striped. The Royal knife fish are overall striped on their body.
They are nocturnal and generally driving through the twilight time. They actually hunt live prey and will try any fish that fits into their mouths. Young clown knife fish usually school near water logs and plants for security, whereas more mature specimens usually become territorial and eventually become loners. These fish can also breathe air to survive in stagnant waters and little oxygen. The clown knife fish prefers water around neutral pH and temperature ranging from 75 to 85 °F (24 to 29 °C) pH: 6.0 – 8.0. These fish usually are found in lakes, swamps, and river backwaters. An obligate, typically nocturnal, predator feeding on smaller fishes, crustaceans and other invertebrates in nature but in most cases adapting well to dead alternatives in captivity. They are generally peaceful and will do well with other fish that are not particularly aggressive and that is too large to fit into its mouth. Do take caution as they have poor eyesight and will sometimes try to eat bigger fish then they can handle. They can ultimately injury or kill a fish they are unable to eat.