In the wild the fish length may reach 1 m (3.3 ft), however at tank conditions it grows smaller, usually about 50 cm (20 inches) long. Its lifespan is about 10 years.
The fish has humpbacked elongated body flattened from sides with small scales; it has silvery-gray color. There is also an albino kind of the fish; it has a row of round dark spots with white edging along its body, their number varies from 6 to 15.
The dorsal is so small that it rather resembles a small feather, than a fin. Things are quite the opposite as for the fish anal fin – it is rather long: it stretches starting from pectoral fins and smoothly transfers into the tail fin. The fin moves all the time, due to this the fish can swim.
Anal fin of the young species has bright pattern on it, that consists of lots intersecting lines. The brighter is the pattern on the anal fin of rising fish species, the more pronounced and large spots on their body they will have when they become reproductive. Pectoral fins allow the fish to perform various moves when swimming.
Large mouth of clown knifefish has many small teeth. Distinctive feature of the fish is that it can swim both forward and backward.
The fish respiratory organs are constructed so, that it can breathe with oxygen saturated in water and with atmospheric air. You can often see how you pet rises to the water surface to gasp an air bubble.