FishFreshwaterExpert
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Clown Knife Fish
Chitala ornata
The 'Phantom Blade' of Asia (90-100 cm / 3+ feet). A mind-bending prehistoric oddball fish that looks exactly like a giant, gleaming silver crescent knife. It has almost no back fins, instead using a single, massive, rippling curtain-like belly fin to glide forward or completely backward through the water like a ghost. It is famously adorned with massive, white-ringed black 'polka dots' down its tail. Totally blind and fearful of light during the day, it turns into an unstoppable, vacuum-mouthed nocturnal assassin the second the lights go out.
Water Temperature
24 - 28 °C
pH Value
6 - 8
Water type
Freshwater
Tank level
Bottom and middle
Adult size
100 cm
Minimum tank volume
>= 500 L
Minimum group
>= 1
GH
2 - 15 dGH
KH
1 - 7 dKH
TDS
40 - 295 ppm
Conductivity
63 - 461 uS/cm
Species description
Geographical Origin and Habitat: Widespread throughout Southeast Asia (Mekong, Chao Phraya). Inhabits large slow-flowing rivers, lakes and swamps rich in vegetation.
Taxonomy and Morphology: Clown Knife Fish (Chitala ornata). Giant of the Notopteridae family. Easily reaches 1 meter (40 inches). Knife-blade compressed body, with a very long anal fin that it uses to swim in both directions.
Social Behavior: Nocturnal and crepuscular. Juveniles are gregarious, but adults become highly territorial and intolerant towards conspecifics or other similar fish. Swims sinuously on the bottom.
Coloration and Sexual Dimorphism: Silvery-gray background decorated with a row of large black "eyes" (ocelli) bordered with white along the base of the anal fin. The number of ocelli varies (from 5 to 10). Sexual dimorphism absent.
Care, breeding and tankmates
Aquarium Setup: Monster Tank species (minimum 200-250 cm / 80-100 inches in length). Needs huge PVC pipes or large submerged roots to hide during the day. Poor lighting and free swimming space.
Diet and Feeding: Voracious nocturnal predator. Wean it with dead small fish (smelt), shrimp, mussels and sinking pellets for carnivores. Will eat any fish that fits in its mouth.
Water Quality: Robust, tolerates a wide range of pH (6.0-8.0). Produces an enormous organic load: a giant sump and frequent heavy water changes are a must.
Compatibility and Cohabitation: Coexists only with colossal sized fish that it cannot swallow: large Plecostomus, Pacu or large South American Cichlids. Conspecifics should be avoided.
Aquarium Breeding: Impossible in domestic aquariums. In nature the male cleans a nest on the bottom or on submerged wood and fiercely defends the eggs (up to 10,000) and larvae for weeks.
Risks and Diseases: Very susceptible to Ich (White Spot) and sensitive to copper and malachite green based medicines due to its tiny scales. Use halved doses.
Geographic Origin and Distribution
Widespread throughout Southeast Asia (Mekong, Chao Phraya). Inhabits large slow-flowing rivers, lakes and swamps rich in vegetation.
Origin
Cosmopolitan or introducedNorth AmericaSouth and Southeast Asia
Fish profile
- Temperament
- Semi-aggressive
- They are primarily nocturnal predators that are shy and retiring during daylight. They can be very aggressive towards other knifefish but peacefully ignore large, differently shaped species. Providing adequate hiding spaces is essential to reduce their inherent stress.
- Diet
- Omnivore
- These formidable carnivores prefer a diet of meaty foods like earthworms and chopped fish. They generally refuse dry foods initially but can be trained to eat large carnivore pellets. Feeder fish should be avoided to prevent the introduction of dangerous parasites.
- Life expectancy
- 10-15 years
- The Clown Knifefish is a long-lived species that can survive between 10 and 15 years in captivity, with some specimens exceeding this range under ideal conditions. Their long-term health depends heavily on water quality and the availability of space suited to their massive adult size. Excellent biological filtration and consistent water changes are essential to prevent stress from toxin accumulation. Skin diseases and bacterial infections can occur if the substrate is not kept clean.
- Adult size
- 100 cm
- The catalog's scalar value is 100 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 100 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Chitala ornata (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Solitary
- They are nearly impossible to sex and are generally highly intolerant of their own kind. It is highly recommended to keep only a single specimen per aquarium. If kept together, intense and often fatal fighting will occur unless the tank is massive.
- Feeding frequency
- Twice daily
- Young Knifefish require daily feedings to support their rapid development. Adults should be fed a large meal two to three times per week. Feeding at dusk or during the night often yields the best results.
- Bioload
- Extreme
- The Clown Knifefish grows extremely large and produces a massive bioload. An oversized mechanical and biological filtration system is absolutely critical. Weekly large-volume water changes are mandatory to keep the environment healthy.
- Flow
- Stagnant
- They favor calm to moderately moving water, similar to their native Southeast Asian rivers. Avoid overly turbulent conditions that can stress these flat-bodied swimmers. Gentle circulation that keeps the tank clean without overpowering them is ideal.
- Reproduction
- Oviparous
- Breeding is incredibly rare in captivity due to the colossal tank size required. They are egg layers that deposit adhesive eggs on hard substrates in the wild. The male will fiercely guard the eggs until they hatch several days later.
- Compatibility & tankmates
- They are predatory but surprisingly peaceful towards large, robust tank mates. Any fish small enough to fit into their large mouths will be eaten at night. Excellent companions include large pacus, oscars, and giant gouramis.
- Tank level
- Middle/Bottom
- They are reclusive during the day, resting in the middle or bottom levels among hiding spots. They require large, opaque tubes or dense driftwood snags to feel secure. At night, they actively patrol all levels of the aquarium searching for prey.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.7 ± 0.57 se
- Resilience
- Medium (1.4 - 4.4 years)
- Phylogenetic uniqueness (PD50)
- 0.5166
- Bayesian Length-Weight
- a = 0.00479, b = 3.05
- VulnerabilityHigh to very high vulnerability (73 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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Recommendations grouped by close relatives, companion choices, and similar care.
