A fascinating nocturnal predator named for its blade-like shape. Lacking a dorsal fin, it moves by rippling its long anal fin, allowing it to easily swim backward and forward. While peaceful with larger tank mates, it is an opportunistic piscivore that will swallow any fish or invertebrate small enough to fit in its mouth. It requires dim lighting and plenty of caves (PVC or driftwood) to feel secure during the day.
African Knifefish At a Glance
African Knifefish Tank Requirements
Will African Knifefish fit in your tank?
Care guides tell you what African Knifefish needs, the next question is whether your tank can safely provide it. Test African Knifefish against your tank size, maintenance needs, and the fish you already keep before you buy.
Useful setup supplies
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African Knifefish Water Parameters
Water care products
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African Knifefish Temperament & Compatibility
African Knifefish Varieties
Each variety inherits the species defaults above. Only differences are highlighted.
Standard (Adult)
The fully grown African Knifefish. A skilled nocturnal predator that must be housed with deep-bodied, medium-to-large peaceful fish to prevent them from becoming meals.
Same care requirements as the base species
Also known as: Adult, Wild Type
Juvenile (Grow-out)
Often sold at a small size (7-10cm). Will grow rapidly and soon start preying on small tank mates like neon tetras or dwarf shrimp. Can be temporarily housed in a smaller grow-out tank.
Differs in 5 traits from base species
Also known as: Baby, Juvenile Knifefish
African Knifefish Care Guide Summary
The African Knifefish, scientifically known as Xenomystus nigri, belongs to the Oddballs family group. Adults reach a maximum size of approximately 30 cm and have a compressed body shape with a moderate growth rate. Classified as semi-aggressive, this species primarily occupies the mid-level and bottom zones of the aquarium and produces a high level of biological waste.
To thrive, the African Knifefish requires a freshwater only aquarium with a minimum volume of 200 litres and a tank length of at least 120 cm. Water temperature should be maintained between 23°C and 28°C, with a pH range of 6–7.5 and a general hardness of 2–15 dGH. A low water flow is preferred.
Due to its specialist needs, the African Knifefish is best suited for fishkeepers who can provide a carefully planned setup. This species is available in 2 varieties: Standard (Adult) and Juvenile (Grow-out). Each may differ slightly in size, temperament, or care needs, so it is worth checking the specific requirements of the variety you plan to keep.
African Knifefish Habitat Setup
When setting up an aquarium for the African Knifefish, a low water flow best suits their natural preferences. Because this species occupies the mid-level and bottom zones, the aquarium layout should prioritise open swimming space in the centre of the tank for free movement and sufficient floor space with hiding spots among rocks, wood, or dense planting. Useful additions include smooth gravel or rounded substrate to protect their sensitive barbels, driftwood, which can serve as both a hiding place and a dietary supplement, and floating plants to diffuse overhead light and create shaded areas.
African Knifefish Compatibility Notes
Classified as semi-aggressive, the African Knifefish is adaptable and can be kept singly or in a small group, offering flexibility when planning a community tank. When choosing tankmates, any fish small enough to fit in its mouth will likely be eaten, ornamental shrimp are not safe companions, conspecific aggression can be intense, especially in smaller tanks, and boisterous or fast-moving tankmates may cause this species undue stress. Selecting tankmates that favour different water layers from the mid-level and bottom zones can help reduce competition and territorial overlap.
African Knifefish Recommended Tank Sizes
Standard aquarium sizes that meet the minimum volume and length requirements for African Knifefish.
55 Gallon Standard
60 Gallon Breeder
75 Gallon Standard
90 Gallon Standard
125 Gallon Standard
150 Gallon High
African Knifefish Feeding & Diet Considerations
The African Knifefish is a predatory species that will readily consume small fish, so nano or bite-sized tankmates should be avoided, will hunt and eat ornamental shrimp, making it unsuitable for shrimp-focused setups, and is primarily active at dusk and dawn, so offering food shortly after lights-off ensures it receives adequate nutrition.
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Frequently Asked Questions About African Knifefish
How big does African Knifefish get?
African Knifefish (Xenomystus nigri) typically reaches a maximum adult size of approximately 30 cm. They have a compressed body shape and a moderate growth rate.
What tank size does African Knifefish need?
A minimum aquarium volume of 200 litres and a tank length of at least 120 cm are recommended for African Knifefish. This ensures enough swimming space and helps maintain stable water conditions.
What water parameters does African Knifefish need?
African Knifefish thrives in freshwater only conditions with a temperature range of 23–28°C, a pH between 6 and 7.5, and a general hardness of 2–15 dGH. A low water flow is preferred.
Is African Knifefish peaceful or aggressive?
African Knifefish is classified as semi-aggressive with an aggression score of 5 out of 10. They can work in community setups but may clash with certain tankmates.
Can African Knifefish live alone?
Yes, African Knifefish can be kept singly or in a group. They are flexible and adapt well to both setups.
Is African Knifefish safe with shrimp?
No. African Knifefish is known to eat ornamental shrimp and is not recommended for shrimp tanks. Even larger shrimp species like Amano Shrimp may be at risk.
Does African Knifefish have any special tank requirements?
Yes. African Knifefish benefits from driftwood (digestion/hiding), smooth gravel (sensitive barbels), and plants - floating in the aquarium. These features help replicate their natural habitat and promote overall health and well-being.
Plants That Suit African Knifefish
These plants pair well with African Knifefish based on shared water preferences, layout fit, and how likely they are to hold up in the same aquarium.
Amazon Frogbit
Limnobium laevigatum
Asian Watergrass
Hygroryza aristata
Asian Watermoss
Salvinia cucullata
Carolina Mosquito Fern
Azolla caroliniana
Common Duckweed
Lemna minor
Crystalwort
Riccia fluitans
Fish Similar to African Knifefish
Black Ghost Knifefish
Apteronotus albifrons
A fascinating nocturnal predator native to the Amazon basin. It lacks a dorsal fin and moves via a continuous undulating ventral fin, allowing it to swim backwards as easily as forwards. It generates a weak electrical field to navigate and hunt in the dark. Scaleless and highly sensitive to medications, it requires smooth hiding places (like PVC pipes or smooth driftwood). Will consume any fish small enough to fit in its surprisingly large mouth.
Clown Knifefish
Chitala ornata
A massive, nocturnal predator native to Southeast Asia, widely known for the distinct row of ocellated spots above its anal fin. While sold as small silvery cute juveniles, they grow incredibly fast into nearly 1-meter giants that require immense aquariums. They are obligate carnivores and will eat any fish small enough to fit in their large mouths. They are shy during the day and require large hiding tubes or caves.
African Pike
Hepsetus odoe
The African Pike is a formidable and fascinating predatory fish native to West and Central Africa. With its elongated, torpedo-shaped body and a mouth full of prominent sharp teeth, it is a surface-dwelling ambush predator that requires a massive aquarium. Best kept by advanced aquarists, they are heavily piscivorous and will consume any fish that fits in their mouths, though they are generally tolerant of similarly sized, robust tank mates.
Featherfin Squeaker
Synodontis eupterus
A striking, large African catfish known for its spectacular, fan-like dorsal fin and its ability to produce a 'squeaking' sound when distressed or asserting dominance. While generally peaceful with similarly sized tank mates, it is highly territorial over its chosen cave and will predate on small fish at night.
African Butterfly Fish
Pantodon buchholzi
A fascinating, prehistoric-looking surface dweller native to the slow-moving waters of West Africa. They are strictly top-dwelling ambush predators with a completely flat back and upturned mouth designed to hunt insects and small fish. A tight-fitting lid is absolutely mandatory as they are exceptional jumpers capable of gliding above the water.
Brown Bullhead Catfish
Ameiurus nebulosus
A highly adaptable, large North American catfish known for its distinct barbels and mottled brown skin. While incredibly hardy and tolerant of a wide range of water parameters, they are massive, opportunistic nocturnal predators. They will consume any tank mate small enough to fit in their cavernous mouths and produce substantial waste.