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Afer Knife Fish | Uncommon And Beautifully Marked Knife Fish |

The scientific name of the Afer knife fish is Papyrocranus after and it belongs to the family of Notopteridae, which is commonly named as featherbacks and knife fish.

The family Notopteridae consists of two subfamilies, four genera, and ten species. The Afer knife fish belongs to the Subfamily Xenomystinae and genus Papyrocranus according to the Greenwood classification 1963.

Usually, the individuals of the family Notopteridae have slender, elongated, bodies which present them with a knife-like appearance. Further, they have specialized swim bladders that extend throughout their body.      

Afer Knife Fish

Afer knife fish are among a small group of teleost fish to be electroreceptive. They are sensitive to electric charges although they do not possess an electric organ.

They use this special ability to locate objects in their vicinity, detect prey, and avoid predators as they have poor eye vision. 

The Albino forms of this species are more common than others. It is the least concerned group in IUCN Red List.    

How to identify Afer Knife?

Afer knife fish is a freshwater fish and it belongs to the knife fish family. It is commonly called a reticulated knife fish due to its unique skin texture.

Its color varies from dark brown to black and has lighter mottled spotting all over the body which gives them a marbled effect.

Only matured fish shows the mottled spotting over their body.  It has no scales. Its body is slender and long.

Afer knife fish has a dorsal fin which projects from its back rather like a feather and therefore they called as featherbacks.

The dorsal fin has no spines and it just has two soft rays. The anal fin of Afer Knife fish is elongated and it has no spines but has few soft rays.

It has a small caudal fin and no pelvic fins. However, the Afer Knife Fish bit differs from other knife fish species.

Most other knife fish species swim by rippling their dorsal or anal fin but this species gets around by undulating its entire body like Arowana or an eel.  It gives the fish a mesmerizing swimming style which steels the attraction of many aquarists.  

Where they live?

Afer Knife fish is native to tropical South Africa.

It is usually found in heavily vegetated, slow-moving parts of rivers and sluggish blackwaters in the Niger basin and other coastal river basins including the Tano River and Pra River basins in Ghana, and the Cross River and Sanaga River basins to the east of the Niger Delta.

It is being recorded in many countries of central and western Africa including  Sudan, the Democratic Republic of Congo, Cameroon, Nigeria, Niger, Benin, Ghana, Ivory Coast, Mali, Liberia, Sierra Leone, Guinea, Guinea-Bissau, Gambia, and Senegal.

They Can Breath air

The After knife fish has a special ability to breathe air at the surface of the water besides breathing in the normal way through its gills.

Its swim bladder especially adapts to act as a lung for this purpose. The swim bladder of these fish is elongated and it extends for the length of the body cavity and has finger-like side projections.

This adaptation allows fish to live in low oxygen environments such as swamps and their survival rate in the dry season is higher than other fish types due to the above reason.

The interesting fact is the swim bladder also can generate sounds squeezing air through a narrow passage into the pharynx. 

How big do Afer Knife get?

It can reach a maximum length of  80 cm (31 in).

But usually, in captivity, it grows to a length of about 62 cm (24 in). The highest reported weight of Afer knife fish is 1.3 kg (2.9 lb). 

Is Afer Knife aggressive?

They are commonly known as semi-aggressive fish.

They can be kept as groups when they are young and when they get mature they become very territorial and aggressive to their own kind and sometimes towards other fish species.

If the size of other tank mates is small enough to their mouth they surely eat them. They are particularly aggressive and intolerant towards other knife fish species especially species of the same genus. 

How long does Afer Knife live?

They usually live around fifteen years in normal conditions.

One look Care guide

Scientific namePapyrocranus after
Common nameMarbled Knifefish
Arowana Knifefish
Pom Pom Knifefish
African Featherfin Knifefish
Care levelIntermediate 
Native toSouth Africa and some countries in  central Africa and western Africa 
Type Freshwater 
Color Dark brown to black with light color spots 
Tank size55 gallons for juvenile 
100-150 gallons for adults 
Preferred temperature75.0 to 86.0°F 
Other water parameters (ammonia ,ect)Ammonia:      0ppm
Nitrite:            0ppm
Nitrate:        <30ppm
pH:                  6.5 to 7.5 
Preferred salinityHardness          5-15 dGH
Size 80 cm (31 in) in wild  
62 cm (24 in) in captivity
Growth rateFairly Slow 
Temperament Aggressive 
Recommended tank matesLarge fish species preferably Arowana Not compatible with other knife fish species 
Preferred foodLive fish Worms 
Feeding frequencyOnce a day, daily 
BreedingNot known in captivity

Afer Knife care

Afer Knife tank size

Usually, 55 gallons tank is suitable for young fish.

However, a larger aquarium is recommended, preferably a 100 gallons to 150 gallons tank for large and mature specimens. 

How many Afer Knife should be kept together?

The Afer knife fish can be kept with its own species as a juvenile.

But it is hard to keep two adults together as they are territorial and aggressive with their own species. More on, they prefer to be lonely as they become mature.

Tank setup

Usually, 100 galloons aquarium will be needed for fully-grown fish. They demand high-quality water hence high-quality filter with low water flow is recommended for their tank.

As they are very sensitive to the medications it is always good to incorporate a UV sterilizer to kill microbes and parasites which causes diseases of Afer knives.  

As the Afer knife fish is a nocturnal fish it prefers to hide in a safe and secure location during the daytime.

Also, they will hide when they are introduced to a new tank and come out only at feeding time for some period until they are used to the new environment. 

Therefore, need to provide them with many hiding places and sheltered areas.

As this species usually swim at or near the bottom of the tank unobstructed swimming room should be provided at or near the bottom of the tank.

It is best to keep plants along the back and sides of the tank to leave some open area for swimming.

As they are soft scale fish the substrate should be consist of soft sand. Further, soft rocks without sharp edges, plants with long twisted roots, aquarium safe woods provide ideal hiding places for Afer knife fish.

Low-subdued lighting is recommended for the tank as they are nocturnal.

Water quality condition

The Afer knife fish is very sensitive to water condition changes as they are scaleless.

It is recommended to change the water about 30-50% weekly. Routine water quality tests are a must to make sure levels are not spiking.

The preferred temperature range is 75.0 to 86.0°F (24 °C to 30 °C ) as they are native to tropical countries of the African continent. 

An aquarium heater is a good solution for keeping the water at the recommended temperature.  They prefer to stay in the pH range of  6.5 to 7.5.

They can not live in brackish water as some of their family members do. Hence they prefer to live in the hardness range of 5-15 dGH.

The recommended ammonia and nitrite range is 0 ppm while the preferred nitrate range is < 30ppm.

High quality UV sterilizer is necessary to keep the tank free of bacteria and other parasites as it is always good to prevent diseases rather than having the resort to chemicals after a disease outbreak.

Afer Knife breeding 

Afer Knife male or female identification

Unfortunately, there is no way to identify between male and female of After knife fish as they do not show sexual dimorphism.

Both males and females show the same skin texture and same fin structure. They only can be identified examination of gonads after dissection in a laboratory.

However, according to the literature, the electroreceptive ability of mature males is higher than that of mature females.

Therefore, the response time for prey or alien object is high for mature females than that of mature males.

Identify pregnant Afer Knife  and Afer Knife  pregnancy stages

It is very rare and not reported that the Afer knife fish breed in captivity.

However, the lower abdomen of female fish becomes larger when it bears eggs.  According to literature sometimes, when a female fish is pregnant, she will develop a “gravid spot” on the abdomen.

However, it is hard to identify the gravity spot development in female After knife fish as they are dark in color. 

Afer Knife breeding

In their natural environment, the Afer Knife fish produces a small number of relatively large eggs.  The average fecundity is 500 eggs/kg of body weight.

The average diameter of eggs is 3.6 mm (0.14 in). The large eggs result in large larvae which may have a better chance of survival in inhospitable surroundings.

They usually live in slow-moving sandy rivers and migrate to flooded black water forests during the rainy season for breeding.

Like many knife fish species, it is very hard to breed them in captivity and there are no cases reported for their breeding in captivity.

However, if you still want to breed them few tips are given below. 

  1. Keep your aquarium dark and away from the noise and excessive movement.
  2. Keeping the water around 27 ℃ – this is the optimum breeding temperature.
  3. Perform 50% water changes every couple of days to indicate the wet season as they breed in the wet season in their natural environment. 
  4. Place enough soft rocks and plants to provide a suitable place to lay eggs and to make the environment similar to their natural environment. 

How many fry does Afer Knife have?

Since the breed in captivity is unknown the number of fry and fry care is also unknown.


Since the Afer knife fish has no scales, it is more prone to diseases than other scale fish.

They are the fish that shows the first signs of skin disease as the parasites can attack them more easily because of their scaleless skin.

It is common to see that these fish twitch and rub around the tank in case of disease. They respond well to most of the medication and normally heal quickly.

Copper or copper included medicines can not use for this species as they are very poisonous to this species.

Afer knife fish are hardy fish species and though they are attacked by many diseases they heal quickly in a well-maintained aquarium. 

However, the aquarist should take care when introducing new fish or things to the aquarium. Not only other fish but also plants, substrate, and decoration can harbor bacteria.

Therefore, the decorations plants and substrates should be cleaned well before putting them in the tank. The fish should introduce to the tank after quarantining them in a suitable manner.

Another method to enter parasites into the tank is food. Since they love to feed with live food make sure to quarantine live food before feeding.

If the Afer knife fish catch directly from the wild it can harbor parasites and need to take safety measures to avoid other tank mates being attacked by diseases. 

As most Afer knife fish are prone to skin flukes, parasitic infestations(protozoa, worms, etc.), ichthyology infection, bacterial infections(general), and bacterial diseases it is recommended to keep eye on them to detect such disease.

Early identifying the signs of disease and treating them early makes a huge difference. 

Special tips

Due to the aggressiveness and the size of Afer knife fish, it is suggested to keep these monsters only with aquarists who have some experience.

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, an issue, feeding them at night may be necessary.  

Feeding behavior of Afer Knife 

What do they eat

The Afer knife fish are carnivores. In their natural environment, they feed on insects, worms, and small fish.

They begin to eat when the sun sets and continue throughout the night as they are nocturnal animals.

Their favorite food is live fish but can be trained to eat earthworms or bits of frozen or defrosted foods.

But it depends on the preference of individuals and some may refuse to eat frozen foods but it is always good to train them to eat frozen foods as soon as they introduce to the tank. 

They rarely eat any type of dried foods such as tablets or pellets. It is always good to feed them with live fish at least once a week even if they accept dried foods to let them catch the prey as they in their natural environment.

If they accept dried fish they should be fed with hundred percent meaty food as they are carnivores. 

For the best results, diet rotation on daily basis is important. It is important to feed them with feed only what they can consume in two to three minutes and otherwise the excess amount of food reduce water quality.

How often should you feed

They should be fed daily. Feeding once or twice a day will be enough.

When should you feed (time of the day)

It is good to feed them in the sunset or at night with the lights turned off as they are nocturnal and prefer to eat when it is dark.

How long they can go without food

As they are carnivores they can be live a fairly long time than the herbivores without food. However, the time can be different depending on the individual.

What fish can live with Afer Knife?

The Afer knife fish is a fish with an attitude. It always requires special attention when selecting tank mates as it is aggressive.

It has a large mouth compared to its slender body. Since the live fish is the favorite food of this species, they will not reluctant to eat any fish which fit their large cavernous mouth. 

However, juveniles of this species 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 toward other kinds of knife fish species. Anyway, there are some instances that they are aggressive towards other kinds of fish species too.

They only can be kept with other kinds of large fish which do not fit into their mouth and also with the species which are not aggressive towards Afer knife fish.

Many aquarists suggest that they can be housed with Arowana. However, there are some incidents reported that they have even been attacked by the Afer knife fish.  

Credit to : Justin MFK
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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.