Clown Knifefish

Geographical Origin & Biotope:

Native to the largest river basins of Southeast Asia: the Mekong, Chao Phraya, and Mae Klong rivers, extending across Thailand, Laos, Cambodia, and Vietnam. It opportunistically inhabits both the main channels of slow rivers and lakes, preferring turbid depths obscured by submerged branches. It has escaped captivity and become a fierce invasive pest species in warm places like Florida.

Taxonomy & Morphology:

Belonging to the Notopteridae family, the Old World knifefishes. Physically it is formidable: it possesses a curious silhouette with a back strongly arched immediately behind the "neck", giving it the appearance of a "hunchbacked" wrestler. It lacks true pelvic fins, but boasts a tiny feather-shaped dorsal fin on the center of its back. Propulsion derives from the boundless ventral fin that starts behind the head, fuses the anal and caudal regions, and reaches the extreme tip of the tail, allowing the famous wave-like swimming forwards or backwards. It possesses the accessory ability to gulp atmospheric air if oxygen in the water is scarce.

Social Behavior:

In solitary captivity, once accustomed to the owner and feeling secure in its daytime hideout, it will show remarkable intelligence, emerging from its den to beg for food, approaching gently with its graceful undulating movements. It remains a solitary and inflexible hunter.

Coloration & Sexual Dimorphism:

The livery is a sparkling metallic platinum or silvery-grey (with adulthood it darkens to a gunmetal grey). The "Clown" element that gives the animal its name is the splendid series of 5-10 huge, perfectly circular, pure white-ringed black spots (ocelli) along the entire lower rear half of the body. Pups do not have these ocelli, but only faint temporary vertical stripes. There is no sexual dimorphism.

Tank Setup:

It is considered a "Tank Buster". Most aquarists are not equipped to house this fish for its entire life cycle. The tank's footprint for an adult is fundamental: a depth (front to back) of less than 80-90 cm (32-36 inches) will not allow the fish to make a U-turn without painfully bending its spine. The setup must be bare to provide unlimited swimming space, with the sole exception of a daytime hideout large enough to contain it (large black PVC pipes) and very shielded lighting or floating plant cover. Any internal glass heater will almost certainly be smashed by its movements: use external inline heating systems or heavy titanium guards.

Diet & Feeding:

In the wild, the diet of *C. ornata* is entirely piscivorous (fish-eating). Often pups categorically refuse dead food and many owners raise them feeding them cruelly (and dangerously regarding disease) on live feeder goldfish. Training them to accept dead food from tweezers is vital for economic and sanitary sustainability. Once acclimated, they will swallow whole silversides, chunks of tilapia, huge prawns with the shell on, and beef heart (sparingly). During the night, they will patrol the bottom sucking up food. They can fast for weeks without problems if they are satiated.

Water Quality:

They tolerate a fair variety of Asian water parameters, but cannot stand spikes in nitrogenous compounds resulting from their copious defecations. The ideal pH is around neutral (6.5 - 7.5), medium-soft hardness, and standard tropical temperatures (24-28°C / 75-82°F). A massive sump equipped with strong mechanical pre-filtration is needed to avoid clogging the biological media. Excellent jumpers: cover the tank with heavy, weighted glass lids.

Compatibility & Tankmates:

The sad fate of many fish is to disappear at night into the enormous mouth of the Knifefish. The mouth extends and its oral cavity runs down much of the lower belly: prey are swallowed whole. *Never* keep it with conspecifics, they would fight savagely. Permitted tankmates are armored and pelagic colossi: Arowanas (which stay high and are generally ignored), XXL Datnoids, large Plecostomus (with caution, plecos sometimes attach to the knife's smooth flanks to scrape its mucus, fatally injuring it), or river stingrays.

Aquarium Breeding:

Impossible at the hobbyist level. In Thailand and their countries of origin, they are bred in immense outdoor ponds, where males clear submerged logs on which females release adhesive eggs; the males protect the nests fiercely by fanning fresh water with their long anal fin.

Risks & Diseases:

It is incredibly prone to injuring itself due to moments of panic (blind darting, "spooking"), which lead it to crash into sharp decor or the glass, peeling the skin off its protruding snout and inviting lethal secondary fungal attacks. Once again, lacking true scales, the indiscriminate use of copper in case of illness is forbidden.