African Brown Knifefish (Xenomystus Nigri)

Description

The African Knife Fish can reach up to 12 inches (30 cm) in the wild, but aquarium raised specimens are usually smaller, reaching around 8 inches (20 cm). The uniform blackish gray brown body of the African Knifefish is flat and elongated with an arched back. It has a continuous fin along the underside formed by a joining of the caudal and anal fin. It is a graceful swimmer and this fin allows it to move both forwards and backwards. These fish have no dorsal fins.

It has a large mouth and two short barbels used for hunting. When not hiding it will normally be seen swimming with its head down and barbels close to substrate hunting for food. The barbels help to locate food. Like other knifefishes, it is a nocturnal predator that also uses electrical fields to navigate and find prey.

Its scales are very small giving them an almost scaleless appearance with the only break being the lateral line. The lateral line is this fishes most important sensory apparatus, It has nerve filled pits throughout which gives it the ability to swim in lightless waters by emitting electrical pulses. An interesting characteristic is its ability to emit a bell-like or barking sound, produced by ejecting air from its swim bladder.

• Size of fish – inches: 11.8 inches (30.00 cm) – In the wild, the African Knifefish can grow as large as 12″ (30 cm), but a maximum size of around 8″ (20 cm) is more realistic for a tank raised specimen.
• Lifespan: 10 years – Their average life expectancy runs between 3 – 7 years, with an occasional lifespan of 10 years.

Fish Keeping Difficulty

These knifefish are very hardy after the first 30 days in a new environment. These fish are mainly wild caught and can be very timid and hard to fed at first. So there is a high mortality rate during this acclimation time. Once you get past the first 30 days they are very easy to take care of. Making sure they are getting their share of the food is the hardest part. They are not only shy but also normally only eat at night unless trained to eat during the day, which can be done.

• Aquarium Hardiness: Moderately hardy
• Aquarist Experience Level: Intermediate

Foods & Feeding

The African Knifefish are carnivores. In the wild they begin to eat when the sun sets and continue throughout the night, feeding on worms, crustaceans, insects and snails. A tank of around 55 gallons is large enough to keep an adult in good condition for all of its life. They are one of the few species of knife fish that will eat dried foods such as flakes and sinking pellets. A varied diet is important so be sure to also feed some fresh or frozen foods such as brine shrimp or bloodworms. They will eat small fish but this is more of a warning that small tank mates may disappear, not a suggestion for feeding.

• Diet Type: Carnivore
• Flake Food: Occasionally
• Tablet / Pellet: Yes
• Live foods (fishes, shrimps, worms): Most of Diet
• Meaty Food: All of Diet
• Feeding Frequency: Daily

Aquarium Care

This species of knifefish needs clear and pristine water to survive. High quality filters are necessary and there needs to be away that the filters do not create to much of a current. Weekly 30 – 50% water changes should be done, depending on the bio load. These fish are very sensitive to water changes and the water should be tested often to assure that you will have a healthy fish.

• Water Changes: Weekly – Do a 30 – 50% water change weekly.

Aquarium Setup

The African Knife fish will spend most of its time near the bottom, although they will occasionally swim to the surface to grab a gulp of air. A tank of around 55 gallons is large enough to keep an adult in good condition for all of its life. The African Knife fish does best in a well planted tank with hiding places among rocks and drift wood and some open area for swimming. These fish do need a good amount of unobstructed swimming room as well. Plants are best especially along the back and sides to leave some open area for swimming.

Plants with long twisted roots are best and offers hiding places for your Knife Fish. These are nocturnal fish and appreciate floating plants to break up and help subdue any light. Clay flower pots make great caves for these fish so they have a safe place to take refuge. Soft sand is the best choice for substrate. To get the most enjoyment out of this fish add some Moonlight LED lights to make viewing this fish easier as they will tend to hide when normal tank lights are on.

• Minimum Tank Size: 55 gal (208 L)
• Suitable for Nano Tank: No
• Substrate Type: Any
• Lighting Needs: Low – subdued lighting – Prefers low lighting but can be comfortable in aquariums with moderate to high lighting if there are places to hide. Add Moonlighting LED lights to get a good viewing of your knife.
• Temperature: 72.0 to 82.0° F (22.2 to 27.8&deg C)
• Range ph: 6.0-8.0
• Hardness Range: 5 – 15 dGH
• Brackish: No
• Water Movement: Weak
• Water Region: Bottom – This species of knifefish will spend most of its time near the bottom, although they will occasionally swim to the surface to grab a gulp of air.

Social Behaviours

They are peaceful towards other species but adults will sometimes turn aggressive towards others of their own kind. Younger fish like to be in groups, but as they mature they become solitary fish. Knife fish can co-habitat if that are given about 55 Gallons per knife. They do have a relatively large mouth so smaller tank mates may disappear. Some of the Mormyridae fishes, such as the Elephantnose and the Baby Whale make good tank mates as do Synodontis catfish.

• Venomous: No
• Temperament: Semi-aggressive
• Compatible with:
  • Same species – conspecifics: Sometimes – Get along when young, and adults can co-habitat if that are given about 55 Gallons per knife.
  • Peaceful fish (): Monitor – The African Knifefish is a carnivore and it will eat smaller fish.
  • Semi-Aggressive (): Threat
  • Aggressive (): Threat
  • Large Semi-Aggressive (): Threat
  • Large Aggressive, Predatory (): Threat
  • Monitor – They are peaceful with larger tank mates that are big enough to not be considered food.
  • Shrimps, Crabs, Snails: Threat – is aggressive – In the wild, this fish hunts at night for worms, crustaceans, insects and snails.
  • Plants: Safe

Sexual Differences

Sexual differences are unknown. During spawning the female will become rounder and more colorful then the male.