African Knifefish Care Guide - Aquarium Setup, Diet & Breeding

The African Knifefish is an unusual, elongated fish with a dark brown to almost black body and a strongly compressed, blade-like shape. Its dorsal fin is absent, while the long anal fin runs along much of the underside and provides a distinctive rippling method of movement. The tail is relatively small, giving the fish its characteristic knife-shaped profile.

This species is primarily nocturnal and often spends daylight hours hidden beneath roots, overhanging vegetation or other shaded structures. After dark it becomes more active, moving with smooth undulations of its anal fin as it searches for prey and explores its surroundings.

African Knifefish possess a weak electric sense that helps them navigate and detect nearby objects in dark or murky water. Their small eyes are useful, but electrolocation is particularly valuable in the dim environments where they naturally live.

In the wild, Xenomystus nigri is associated with quiet, structurally complex waters rather than fast-flowing open channels. It is a predatory fish with a striking appearance and an individual personality, although it can become territorial toward its own kind and smaller tank inhabitants.

African Knifefish are native to freshwater habitats in tropical West and Central Africa, including parts of the Niger, Congo and other surrounding river basins. They inhabit slow-moving rivers, streams, swamps and flooded forest areas with heavy cover.

A single African Knifefish should have an aquarium of at least 250 litres, with a footprint of approximately 120 × 45 cm or larger; a bigger, longer aquarium is preferable as the fish grows. Use a secure lid because this species can jump, and provide subdued lighting, gentle water movement and numerous retreats made from caves, driftwood, rockwork and robust plants. A soft sand substrate or smooth fine gravel is suitable, while sharp decorations should be avoided because the fish has delicate skin and spends much of its time weaving through cover. Maintain a stable temperature of 23–28°C and a pH around 6.0–7.5.

Up to 30 cm (12 inches) in total length. Females are often somewhat deeper-bodied, while males may be slightly more slender; reported size differences are not always consistent.

This species is a carnivore and prefers meaty foods. Offer a varied diet of high-quality sinking carnivore pellets together with frozen or live foods such as bloodworms, earthworms, blackworms, mysis shrimp and chopped prawns. It usually feeds most readily after the aquarium lights have dimmed, so evening feeding suits its natural nocturnal habits. Uneaten food should be removed promptly to protect water quality.

African Knifefish can share a suitably spacious aquarium with peaceful, medium-to-large fish such as Congo Tetras, larger barbs, peaceful larger gouramis, medium-sized rainbowfish and calm African cichlids that are not excessively aggressive. Avoid very small fish, shrimp and other creatures that could be swallowed, as well as fin-nipping species and highly boisterous tankmates. Multiple African Knifefish may become territorial, so keeping one is generally safest unless a very large, heavily structured aquarium is available.

African Knifefish are difficult to breed in home aquariums, and reliable captive-breeding accounts are uncommon. A mature male and female may spawn in a secluded cave or among dense cover, depositing adhesive eggs on a sheltered surface. Stable, well-maintained water, plentiful hiding places and a varied diet are important conditioning factors. The parents may eat the eggs, so any serious breeding attempt should use a separate spawning setup and remove the adults after spawning; the eggs hatch after roughly one to two weeks, depending on temperature.

African Knifefish show little obvious sexual dimorphism. Mature females are often fuller through the abdomen, particularly when carrying eggs, while males may appear slightly slimmer, but reliably sexing individual fish by appearance alone is difficult.