fish Easy level

Xenomystus nigri (Günther 1868)

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African Brown Knife Fish, Black Knife Fish, Brown Knife Fish

Xenomystus nigri is a fascinating fish with an unusual form and way to move. It is a member of the Notopteridae family and can be easily distinguished from its Asian parent Notopterus notopterus: African Knife fish lacks a dorsal fin and is smaller. It is a graceful swimmer, thanks to its long continuous fin along the underside. It is a hardy species that in Nature survives in wide range of conditions. This fish is widely distributed in tropical Africa, in the Nile, Chad, Niger, Ogowe and Congo basins. Also present in coastal rivers in Sierra Leone, Liberia, Togo, Benin and Cameroon, but not found in Côte d’Ivoire nor Ghana.

Submitted by
Benedetta Spelta

Water Chemistry

Water information

Water type
Fresh water
Water color
Clear water
Water transparency
Concentration of sediments
Water temperature
25.7 - 28.5 °C
Water flow/curent

Chemical parameters

5.8 -7.5
32 - 65
Dissolved Oxygen


Standard length
20 cm
Water volume (min. aquarium)
200 l
Social behaviour
Lives single
Behaviour description

Ideally the tank should contain some areas of dense planting, stones and driftwood that can be used to create caves in which the fish seek refuge. Younger fish prefers to stay in groups, the grown specimens become solitary fish. When matures Xenomystus nigri becomes increasingly territorial, especially towards the same species.

Aggression grade
Night active
Sexual dimorphism

Females appear plumper and more colourful when ready to spawn.

Nutrition in Nature

Feeds on worms, crustaceans, insects and snails.


Breeding tank set-up

To breed this Xenomystus nigri would prefer the areas with dense planting and caves in which the fish can seek refuge. At the very least provide dim lighting and cover in some shape or form.

Nutrition parents

Life and frozen food diet.

Mating type
Spawning behaviour

The pair produces characteristic barking sounds during the courtship. The male will then guard the eggs which are laid on the surface of wood or rocks and will tend them by fanning them with his fins. Once the eggs are hatched the parents should be removed.

Breeding habits
Hatching period
240 hours
Number of eggs in average
min 150/max 200
Parental care
Fry number
Nutrition fry

The fry should be fed brine shrimp nauplii or microworm as first foods.

Notes on reproduction

Xenomystus nigri with small fish that could be regarded as food.