Reticulate Knifefish

The Reticulated Knifefish gets around by undulating its body in a waving motion!

The Reticulated Knifefish Papyrocranus afer is not the usual Knifefish. Most knives swim by rippling their dorsal or anal fin but this species gets around by undulating its entire body. This is much like an arrowana or an eel. Perhaps that is what led to its being called the Pom Pom Knife. It is also known as the Marbled Knifefish, Arowana Knifefish, Pom Pom Knifefish, and African Featherfin Knifefish.

The African Featherfin Knifefish is a member of the Notopteridae family which contains some of the more outgoing species. This species, like its relative the Clown Knifefish, can grow to huge proportions. Although the Reticulated Knifefish doesn’t get quite as big, it is still a very large fish. It can get up to about 32 inches (80 cm), weighing just under 3 pounds (1320 g). A 55 gallon sized tank or more will be okay for a juvenile, but as an adult and for its full lifespan, it will need a much larger aquarium of 100 gallons or more.

As indicated by its common name Marbled Knifefish, this fish has a dark brown to almost black body with lighter mottled spotting, giving an almost marbled effect. Its body is flat and elongated body with an arched back. Like other members of its family the caudal and anal fin are joined to make one long continuous fin along the underside. It also has a small dorsal fin. The fish pictured above is an albino form, so it does not have the normal marbled patterning.

The Reticulate knifefish is a fish with an attitude and requires special attention when selecting tank mates. Its large eyes and cavernous mouth are indicative of its predatory nature. It may bully other tank mates and will definitely snack on any that will fit in its mouth. When young these fish can be kept in groups, but as they age they become very territorial and aggressive to their own kind and any other fish around them. They are particularly aggressive towards other knifefish, and become intolerant of others of its same genus. Experienced fish keepers report success keeping them with an ArowanaOsteoglossum bicirrhosum that is similar in size. There are however, reports of the Reticulated Knifefish attacking an Arowana tankmate.

Reticulate knifefish can develop into a stunningly patterned fish as an adult, but due to its potential size and aggressive nature, it is recommended for a more experienced fishkeeper. Not only do they require a very large aquarium, but they can be hard to get adjusted to a new tank. Being nocturnal they need places to retreat during the day as well as open areas for swimming. Once acclimated, they are very hardy fish.

For Information on keeping freshwater fish, see:
Freshwater Aquarium Guide: Aquarium Setup and Care

Habitat: Distribution / Background

The Reticulated Knifefish Papyrocranus afer was described by Günther in 1868. The are found in West Africa including the Niger basin and most coastal river basins from Senegal to Ghana. This species is listed on the IUCN Red List as Least Concern (LC). It has a wide distribution and no known major widespread threats. Other common names they are known by include Marbled Knifefish, Arowana Knifefish, Pom Pom Knifefish, African Featherfin Knifefish, and Pom Pom Knife

This knife fish lives in slow moving sandy rivers and migrates to flooded black-water forests during the wet season. Its natural habitat is heavily vegetated and normally pretty dark. The Reticulate Knife is nocturnal and preys on insects, worms and small fish during the night.

• Scientific Name: Papyrocranus afer
• Social Grouping: Varies – As a young fish they may be found in groups, but as adults they are loners.
• IUCN Red List: LC – Least Concern

Description

The Reticulate Knifefish can reach up to can get up to 32 inches (80 cm) and to just under 3 pounds (1320 g). The body 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, and has a very small dorsal fin. Its color is dark brown to almost black with lighter mottled spotting, giving an almost marbled effect. The Reticulate Knifefish pictured above is an albino color form.

While most knives swim by rippling their dorsal or anal fin. This species differs, it gets around by undulating its entire body, much like an arrowana or an eel. All members of the Notopteridae family also use their swim bladder as an accessory breathing organ. This allows the Reticulate to breath air from the surface of the water.

This  fish has poor vision, so to accommodate the poor eyesight it has  an organ that produces an electric field around itself that will detect objects and movements around it. This helps with navigating and hunting, and it also uses this unique electrical field as a way to communicate with other knife fish.

• Size of fish – inches: 31.5 inches (80.01 cm) – These fish can get up to 32 inches (80 cm) and to just under 3 pounds (1320 g).
• Lifespan: 15 years

Fish Keeping Difficulty

The Marbled Knifefish are suggested for an aquarist with some fish keeping experience due to their potential size and aggressive nature. They are normally wild caught and can carry parasites. The Reticulate Knife is a scaleless fish and and can be more prone to disease. Because of the lack of scales they are extremely sensitive to a lot of medications such as cooper. It is highly recommended to have a UV sterilizer in the tank, this will aid in killing many diseases that the knife can get. They are very sensitive to water condition changes as well.

As with many knife fish they are very shy when they are introduced to the tank and it takes time to get them to eat what they need. Being nocturnal by nature makes it even more of an issue, feeding them at night may be necessary.

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

Foods and Feeding

The Reticulate Knifefish are carnivores. In the wild they begin to eat when the sun sets and continue throughout the night, feeding on on insects, worms and small fish. Live fish are their favorite food but some can be trained to eat earthworms or bits of frozen/defrosted fish. Rarely will they eat any type of dried foods. If at first you don’t see them eating, try feeding them live fish at night with the lights turned off.

• Diet Type: Carnivore
• Flake Food: No
• Tablet / Pellet: No
• Live foods (fishes, shrimps, worms): Some of Diet
• Meaty Food: All of Diet
• Feeding Frequency: Daily

Aquarium Care

This fish is scaleless and very sensitive to water condition changes. A high quality filter is a must! Weekly water changes of about 30-50% are needed. Water condition tests should also be done weekly to make sure levels are not spiking.

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

Aquarium Setup

The Reticulate Knifefish will usually swim at or near the bottom of the tank. An aquarium of around 55 gallons will work when they are young, but a full sized Reticulate Knifefish is a big animal which requires a big home. You will need to eventually provide a tank of 100 gallons or more if you plan on keeping one of these beauties into adulthood. Use a high quality filter with low water flow. A UV sterilizer is a smart thing to incorporate into your tank as these fish are very sensitive to medications. The UV sterilizer will kill many diseases.

This fish requires an aquarium with many hiding places and sheltered areas along with unobstructed swimming room. Plants are best especially along the back and sides to leave some open area for swimming. Plants with long twisted roots offer hiding places for your Knife Fish along with smooth rocks or aquarium safe wood. Soft sand is the best choice for the substrate.

They are nocturnal and will spend most of the daylight hours hiding in a safe and secure location. Once acclimated to their new home, they should come out of hiding at feeding time.

• Minimum Tank Size: 55 gal (208 L) – A 55 gallon tank will work when they are small, but they will need a larger aquarium of 100 gallons or more as adults.
• Suitable for Nano Tank: No
• Substrate Type: Sand/Gravel Mix
• Lighting Needs: Low – subdued lighting
• Temperature: 75.0 to 86.0° F (23.9 to 30.0&deg C)
• Range ph: 6.5-7.5
• Hardness Range: 5 – 15 dGH
• Brackish: No
• Water Movement: Weak
• Water Region: Bottom – The Reticulate Knifefish will usually swim at or near the bottom of the tank.

Social Behaviors

The Reticulate knifefish is a fish with an attitude. It requires special attention when selecting tank mates. The mouth is large and its favorite food is live fish. Any fish small enough to fit into that cavernous mouth will quickly disappear. As juveniles these fish can be kept with groups of their own kind, but they become very territorial and aggressive as they mature and grow. They are particularly aggressive towards other knifefish but also towards any other fish they take a disliking to. They should only be housed with other large fish such as the Arowana. However it has been reported that at times they have even attacked these monster fish.

• Venomous: No
• Temperament: Semi-aggressive
• Compatible with:
  • Same species – conspecifics: Sometimes – This knifefish can be kept with its own kind as a juvenile, but as an adult it is very territorial and aggressive with its own species.
  • Peaceful fish (): Monitor – This fish can be rather belligerent as an adult. It will eat smaller fish and may become aggressive towards any other fish it takes a disliking to, especially other knifefish.
  • Semi-Aggressive (): Monitor
  • Aggressive (): Threat
  • Large Semi-Aggressive (): Monitor
  • Large Aggressive, Predatory (): Threat
  • Threat
  • Shrimps, Crabs, Snails: Threat – is aggressive – In the wild, this fish hunts at night for worms, crustaceans, insects and snails.
  • Plants: Safe

Sex: Sexual differences

Sexual differences are unknown.

Breeding / Reproduction

It has not been bred in captivity.

• Ease of Breeding: Unknown

Fish Diseases

The Reticulate Knifefish does not have scales which make it more prone to disease. Knifefish are normally the first fish in a tank to show signs of ick and will twitch and rub around the tank. They respond well to most medication and normally heal quickly. NEVER use copper in a Marbled Knifefish Fish tank. Overall these fish are hardy and disease is not usually a problem in a well maintained aquarium. That being said there is no guarantee that you won’t have to deal with health problems or disease.

Anything you add to your tank can bring disease to your tank. Not only other fish but plants, substrate, and decorations can harbor bacteria. Take great care and make sure to properly clean or quarantine anything that you add to an established tank so not to upset the balance. Because these fish eat live food, disease can be passed to them from their foods. Make sure to quarantine live food before feeding.

When keeping more sensitive types of fish, it is common for all fishes to be infected even before the first warning signs can be noticed. The best way to proactively prevent disease is to give your fish the proper environment and give them a well balanced diet. The closer to their natural habitat the less stress the fish will have, making them healthier and happy. A stressed fish is more likely to acquire disease.

As with most fish the Pom Pom Knifefish are prone to skin flukes, parasitic infestations (protozoa, worms, etc.), ichthyobodo infection, parasitic infestations (protozoa, worms, etc.), bacterial infections (general), and bacterial disease. It is recommended to read up on the common tank diseases. Knowing the signs and catching and treating them early makes a huge difference. For information about freshwater fish diseases and illnesses, see Aquarium Fish Diseases and Treatments.

Availability

The Reticulate Knifefish is commonly available.

References

• Animal-World References: Freshwater Fish and Plants
• Dr. Rüdiger Riehl and Hans A. Baensch, Aquarium Atlas Vol. 1, Publisher Hans A. Baensch, 1991
• Dr. Rüdiger Riehl and Hans A. Baensch, Aquarium Atlas Vol. 3 , Voyageur Press, 1996
• Joseph S. Nelson, Fishes of the World, Wiley, 2006.
• Papyrocranus afer (Günther, 1868) Reticulate knifefish, Fishbase.org
• Papyrocranus afer, The IUCN Red List of Threatened Species