Animal-World > Aquarium Tropical Fish > Knifefish > Black Ghost Knife Fish

Black Ghost Knifefish

Black Ghost, Black Ghost Knife Fish

Family: Apteronotidae (Ghost Knife Fishes) Black Ghost Knife Fish, Apteronotus albifrons, Black Ghost KnifefishApteronotus albifronsPhoto © Animal-World: Courtesy Ken Childs
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hi, i have 2 pair of black ghost knife fish. 2 of them which i brought home a week ago have white spots and their fins are also messed up and both of them have a... (more)  prateek

The Black Ghost Knifefish is the most well known species of knife fish in the aquarium industry!

The Black Ghost Knifefish Apteronotus albifrons is the most popular knife fish. One reason for this is that they have been imported for decades. Other reasons include being unusual, interesting and amazingly beautiful.

It is readily distinguished from other knife fish by the white and black banded area on the caudal puduncle. It also differs from the Brown Ghost Knife Fish, also called the Long-nosed Black Ghost, because of its shorter snout and the Brown Ghost has only one small white band close to the end of its tail.

This fish is also simply known as a Black Ghost. It is a member of the Apteronotidae Family of 'ghost knifefish'. These knifefish received their unusual name because of a rumor that some tribes in the Amazon jungle believe that the souls of the dead inhabit these fish. No one can substantiate this information. It may just be a story created by the people collecting the fish, but it’s a good story!

Though it can get quite big, reaching up to around 20 inches (50 cm), this is a very handsome fish. Like other knife fish, the Black Ghost Knife Fish has a flat elongated body. It has a continuously undulating fin along the underside formed by a joining of the caudal and anal fin. Although it may appear clumsy, it has a built in ‘radar’ system that uses low voltage electricity to help it navigate. This radar system and the undulating lower fin allow it to gracefully move forwards and backwards through the aquarium.

These fish can be shy initially, but once acclimated to a new home they will generally come out to feed. Some have even been know to take food right from their owner's hand. This is a peaceful fish and will not disturb its tank mates. The Black Ghost Knifefish is somewhat sensitive to changes in the water conditions. It is also a big animal that as an adult it will require a large home of 100 gallons or more. But with its good looks and friendly disposition, this knifefish is a distinctive attraction in a large community aquarium.

Until a few years ago, all offered for sale were wild caught and had been imported from South America, mainly from Brazil. The good news is that they are now being bred in Indonesia by the thousands, so much of the pressure has been taken off the wild populations. Odds are that if you see an individual of 5 inches or more offered of sale, it was collected in the wild. Specimens smaller than 5 inches were most likely produced in and imported from Indonesia.

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

Geographic Distribution
Apteronotus albifrons
Data provided by
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Actinopterygii
  • Order: Gymnotiformes (Knifefishes)
  • Family: Apteronotidae (Ghost Knife Fishes)
  • Genus: Apteronotus
  • Species: albifrons
Black Ghost Knife Fish Eating

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A young Black Ghost Knife Fish searching their aquarium for food.

Nice fish and nice aquarium! The video follows a young black Ghost Knife Fish as it surveys the various areas of its aquarium and meets its fellow tankmates while in search for food. There are quite a few awesome shots of both sides of the fish as it swims around and the video does a great job showing what this fish is like on a day to day basis.

Black Ghost Knife Fish - Quick Aquarium Care
  • Size of fish - inches: 20.0 inches (50.80 cm)
  • Minimum Tank Size: 100 gal (379 L)
  • Temperament: Semi-aggressive
  • Aquarium Hardiness: Moderately Difficult
  • Temperature: 73.0 to 82.0° F (22.8 to 27.8° C)
  • Aquarist Experience Level: Intermediate
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Habitat: Distribution / Background

The Black Ghost Knifefish Apteronotus albifrons was described by Linnaeus in 1766. They are found in South America throughout much of the Amazon River and its tributaries. The species is not listed on the IUCN Red List. Other common names they are known by are Black Ghost and Black Ghost Knife Fish.

This knife fish lives in swift moving sandy rivers and migrates to flooded forests during the wet season. Like most Knife fish they like heavily vegetated areas with a lot of hiding places. Their natural habitat is normally pretty dark and these fish have poor vision, so they use an organ that produces an electric field around themselves that will detect objects and movements around it. It helps with navigating and hunting and they also use this unique electrical field as a way to communicate with other knife fish. They are nocturnal and prey on insect larvae, insects, worms and small fish.

  • Scientific Name: Apteronotus albifrons
  • Social Grouping: Solitary
  • IUCN Red List: NE - Not Evaluated or not listed


The Black Ghost can reach up to around 20 inches (50 cm) and has a lifespan of 15 years. Its body is flat and elongated. The caudal peduncle gets very thin, almost 'rod-like'. It has a continuous fin along the underside formed by a joining of the caudal and anal fin and moves with an undulating motion. Although they appear clumsy, they have a built in ‘radar' system that uses low voltage electricity to help them navigate. This and their undulating lower fin allow them to gracefully move forwards and backwards through the aquarium.

True to its name, it has a black body, though occasionally there is a white stripe starting from the tip of its nose and running along the top of its back. It has a broad whitish band just in front of the caudal fin (tail fin) and another narrower white band just before the tip of the tail.

  • Size of fish - inches: 20.0 inches (50.80 cm)
  • Lifespan: 15 years

Fish Keeping Difficulty

This knife fish is really best for an aquarist with some fish keeping experience. The Black Ghost 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. Those that are wild caught can carry parasites. 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. It can take time to get them to eat what they need. Being nocturnal by nature makes it even more of an issue and feeding at night may be necessary.

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

Foods and Feeding

The Black Ghost Knifefish are carnivores. In the wild they are nocturnal, when the sun sets and throughout the night they feed on insect larvae, insects, worms and small fish. In the aquarium this is a fish that prefers fresh or fresh frozen foods such as bloodworms, brine shrimp or blackworms.

Once acclimated to their new home, they should come out of hiding at feeding time. Some have even been taught to feed from their keeper’s hand. These fish are known to create such a bond with their owners that they will eventually lay in their owners hand and eat. Make sure to have no soaps or perfumes on your hands if you do this and sanitize before handling the fish.

  • Diet Type: Carnivore
  • Flake Food: No
  • Tablet Pellet: Yes
  • Live foods (fishes, shrimps, worms): Most of Diet
  • Meaty Food: All of Diet
  • Feeding Frequency: Daily - When acclimating the Black Ghost Knifefish, offering it several feedings a day can help it get comfortable with coming out more.

Aquarium Care

This fish is scaleless and as with most scaleless fish, it is very sensitive to water condition changes. A high quality filter is a must. Weekly water changes of 30 - 50% are needed, depending on bio load. Water condition tests should be done weekly to make sure levels are not spiking.

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

Aquarium Setup

The Black Ghost Knife Fish will spend most of its time near the bottom. But a full sized Black Ghost Knifefish is a big animal which requires a big home. You will need to eventually provide a tank containing 100 gallons or more if you plan on keeping one of these beauties into adulthood. A high quality filter is a must. A UV sterilizer is a smart thing to incorporate into your tank as well, as these fish are very sensitive to medications. The UV sterilizer will kill many diseases.

Provide them with a dimly lit tank and you will have a happy Black Ghost. A fine gravel substrate and many hiding places with plants, smooth rocks or aquarium safe wood is a necessity. Some aquarists will use a clear tube for the fish to hide in. This makes it feel secure, but also the aquarist can see it. They are nocturnal and will spend most of the daylight hours hiding in a safe and secure location. They do apprecaite a moderate to strong water flow as well. Once acclimated to their new home, they should come out of hiding at feeding time. Some have even been taught to feed from their keeper's hand.

  • Minimum Tank Size: 100 gal (379 L)
  • Suitable for Nano Tank: No
  • Substrate Type: Sand/Gravel Mix - Needs a fine gravel substrate.
  • Lighting Needs: Low - subdued lighting
  • Temperature: 73.0 to 82.0° F (22.8 to 27.8° C)
  • Range ph: 6.0-8.0
  • Hardness Range: 5 - 19 dGH
  • Brackish: No
  • Water Movement: Moderate - This is a species that will apprecaite a moderate to strong water flow.
  • Water Region: Bottom - This species of knifefish spends most of its time near the bottom.

Social Behaviors

This is a peaceful fish and will not disturb its tank mates. However Black Ghosts can become aggressive with members of their own species and members of other, similar species. Other than that, they are usually quite timid. They do have a large mouth so small fish or invertebrates kept in the same tank may eventually become a meal for a hungry Black Ghost.

  • Venomous: No
  • Temperament: Semi-aggressive
  • Compatible with:
    • Same species - conspecifics: Yes - Adults may quarrel if they don't have enough space and hiding places to accomodate each fish.
    • Peaceful fish (): Monitor - While it is not necessarily aggressive, it will eat anything small enough to be considered a meal.
    • Semi-Aggressive (): Monitor
    • Aggressive (): Threat
    • Large Semi-Aggressive (): Monitor
    • Large Aggressive, Predatory (): Threat
    • Slow Swimmers & Eaters (): Safe - 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

Sex: Sexual differences

Sexual differences are unknown.

Breeding / Reproduction

This species is being bred commercially in Indonesia but the method used is unknown. There are hobbyists that claim to have successfully bred the Black Ghost Knifefish in an aquarium but they seem reluctant to share the details. There is some information on this subject, scattered reports, but there is nothing yet documented from reputable sources so it will not be reproduced here. One thing for certain is that if you want to give it a try, you’ll need a big aquarium, probably containing 100 gallons or more.

  • Ease of Breeding: Difficult

Fish Diseases

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. The Black Ghost does not have scales which make it more prone to disease. Black Ghost 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 Black Ghost Knife Fish tank.

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.

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 African Knife 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.


The Black Ghost Knifefish are available all year long, especially now that they are being bred in captivity. Odds are that if you see an individual of 5 inches or more offered of sale, it was collected in the wild. Specimens smaller than 5 inches were most likely produced in and imported from Indonesia. Large specimens may command a high price, mainly due to the higher costs of shipping them. Smaller specimens are quite affordable.


Author: Ken Childs, Clarice Brough CFS, Jeremy Roche
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Lastest Animal Stories on Black Ghost Knife Fish

prateek - 2014-12-13
hi, i have 2 pair of black ghost knife fish. 2 of them which i brought home a week ago have white spots and their fins are also messed up and both of them have a red spot at the end of tail. and the 2 other ones, one of which have got his wing cut. what should i do ?

  • Clarice Brough - 2014-12-13
    It sounds like your fish are dealing with aggression because of the messed up fins. These fish are aggressive with their own kind, see the Black Ghost Knife social behaviors section on this page.  Aggression causes stress and is a big contributor to illness. The white spots are most likely ich, though could  possibly be fungus. Check they symptoms and treatments on the Fish Disease and Treatment page, especially for ich.
  • prateek - 2014-12-14
    thanks for the advice ...... :)
Bruce - 2014-02-12
I have a 300mm BGK which I have grown 35mm youngster I bought at the local pet store. I have had him just over two years now living in an comfortably in an Aqua-One 980 (about 230 litres) tank with Phantom glass catfish, Black Widow Tetra's and bristle-nose catfish. He is a fantastic fish spending a lot of time upside in his 100mm diameter clear plastic tube hiding in full view from the world.

Knife Fish Lover - 2014-11-02
Can i keep a BGKF in a 55 gallon with:1 porthole/lesser peacock eel,2 african brown knife fish,6 weather loaches,a pleco,and a lima shovelnose catfish? Oh,and BTW they don't get 20 inches,only 15. Knife Fish Lover

  • Clarice Brough - 2014-11-03
    Ultimately this fish will need 100 gallons or more, see the aquarium setup section on the Black Ghost Knifefish page. Also they do reach 20,' For a second resource, see the size of the Black Ghost Knifefish on Wikipedia.
Linda - 2013-07-12
I have a tank that is 25 gallons, I have 4 BGK in this tank, I love this type of fish and decided to have only this fish. First of all I introduced them to the tank all at once! (all 4) the only other thing in this tank is gravel and 2 ghost houses, (no plants at all) I do have a dual light on this tank however I have disconnected the bright light and only use the black light. I only explain this because everyone has told me that my tank was too small, and that I could only have a small BGK in this tank. I simply love this fish and find them quite hardy in raising so I decided to try and have only this type of fish. During purchasing I made absolute certain to get them all the same size. (rather large) happy to say that all is well! A little chasing, which is fun to watch, but no fighting what so ever. I only feed them frozen blood worms, at first twice a day, but now I feed them only once a day. Is this a miracle or what?! This is contrary to everything that I have been told and read about them

  • Linda - 2014-07-19
    Hey Linda, this is my very same story. I have always had 3 in my tank, which is 25 gallons. which everyone says is small.They are now 2 yrs old and I have had no problems with them being aggressive, except for a bit of chasing. I feed them only bloodworms, and have also disconnected the brighter light, and have 2 clear tubes in the tank with white gravel nothing else is in the tank.I feed them a cube of bloodworns every other day.I think that they too have their own personalities, but I would never incorporate smaller fish, that said any larger fish will bully a smaller one.
Sophie - 2010-02-12
Hi, I've just bought a 4inch knife fish, it's in my 190lt tank. He's with a clown loach, yoyo, pleco, cardinal tetras, harlaquins, and minnows. Was it a bad idear everyone seems fine at the momment. Please messege me sophie=price at symbol msn . com many thanks