The clown knifefish, clown featherback fish or spotted knifefish, Chitala ornata, is a nocturnal tropical fish with a long knife-like body.

Appearance

The clown knifefish is very distinct, normally silvery gray with a long knife like body (laterally compressed) and a long anal fin that gives these fish their common name. Mature fish normally have 5-10 (or even more) black spots ringed with white that usually increase in number and size as the fish grows. Juvenile fish have striped bands instead of spots. Their long anal fins are specially made for graceful forward and backward movements.

The clown knifefish grows to a fairly large size, up to 100 cm and 5 kg in the wild. It has 2 nasal tentacles above their large toothed mouth. In the center of the body there is a flaglike dorsal fin and has no ventral fins. Most clown knifefish are afflicted with cloudy eye color when they age, it is perfectly normal.

Behavior

They are nocturnal creatures and usually cruise during the twilight hours. They normally hunt live prey and will try any fish that fits into their mouths. Young clown knifefish usually school near water logs and plants for security, whereas more mature specimens usually become territorial and eventually become loners. These fish can also breath air to survive in stagnant waters and little oxygen. The clown knifefish prefers water around neutral pH and temperature ranging from 75 to 85 F.

Location

Most knifefish species come from Southeast Asia, specifically Thailand, Borneo, Malaysia, India, and Sumatra.

These fish usually are found in lakes, swamps, and river backwaters. They prefer still waters and can survive with low oxygen.

In the aquarium

Clown knifefish are sold as exotic fishes in pet stores, but they grow much too large for the average home aquarium. It is necessary to keep in mind that these fish will grow fast and very large even in captivity (about 50 cm), so should be kept in aquariums of at least 500 liters in order to reach their full growth potential. It is not advised to have tankmates small enough to be considered food.

These fish enjoy periods of retreat, so aquariums which have caves, plants, or other hiding places are preferred. They are jumpers, so the lid should be kept tightly closed (with weights - larger specimens may knock the lid out). Dim lighting may help lessen jumping issues. For the first few days, clown knifefish are shy and prone to hiding. As they grow larger they tend to be quite the opposite.

These fish have their own personalities, attaching themselves to their handlers to the point of being "hand-held" when moving or doing some maintenance.

Feeding

Clown knifefish are hearty eaters, one of the reasons people like them as pets. They are predatory fish and will take live foods such as feeder fish, ghost shrimp and blackworms. With time they can be adapted to foods such as beefheart and will sometimes learn to accept commercial food pellets. They are mostly nocturnal, thus prefer feeding when the lights are off.

See also

• List of freshwater aquarium fish species

References

• http://floridafisheries.com/fishes/non-native.html – accessed October 2006
• http://badmanstropicalfish.com/profiles/profile5.html - accessed October 2006
• http://www.aqualandpetsplus.com/Knife,%20Clown.htm