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.
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.
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.
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.
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
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.
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.
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.
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
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.
Zoey - 2014-02-05 Please can some one help me my cousin got a angel fish 2day and her black knife keeps attacking it is this normal?
Clarice Brough - 2014-02-05 A Black Ghost Knife can get aggressive with its own or similar species, possibly like those nice flowing fins of the angel! Making sure the tank isn't too small, these guys reach 20' in length, and that there are plenty of hiding placed all around the tank can help.
Lyn - 2015-05-24 Unlike the other poster, I've had no problems with mine with Angels and Silver Dollars. Weird that behaviours are so different!
Dewin Arnold - 2015-02-24 Hiii , I got around 8 BGK fish around 3 to 4 cm in size for my aquarium , my aquarium is around 4 feet in length and 3 feet in height ...... I love the fish but my tank looks empty .... so can you suggest suitable tank mates for my BGK fish.......also I would like to know the max size the BGK fish grow .
Clarice Brough - 2015-02-24 The Black Ghost Knife gets to be a big fish, so tankmates need to be too large for it to eat. Almost any non-aggressive medium to large fish can work, as long as they are not nippy. A school of Silver Dollars or large tetras like the Congo Tetras and Bleeding Heart Tetras. Possibly even Giant Danios might work as long as they don't get pesky. Use the 'fish finder' feature to help you come up with even more ideas.
Lyn - 2015-05-24 I have had mine with Silver Dollars and Angel Fish without incident. I've been reading up on these fish recently (as I think I've got a female either full of eggs or full of gas!!), and they can grow up to 50cm!!!! This would have to be in absolutely ideal conditions in a really large tank. My two, in a community tank of 120 litres, have grown to approximately 20 and maybe 30cm respectively. Good luck.
Cherie Adams Dodd - 2015-03-03 Knife fish and Frontosa as tank mates???
Hello fellow fish lovers :) I am fairly new to fishkeeping and I am asing for advise in relation to my two beautiful black ghost knife fish which I purchaced with a second hand 2ft tank about 7 months ago. One was 7cm and the other 3cm. They have been upgraded to the three foot tank and spend a bit of time in the 4ft tank and have grown and seem very happy. ATM they are in 3ft as we just purchaced 2 frontosa fish, 18cm male & 13cm ?female. We took the knifes out so we could quarentine and medicate the frontosas and other new fish at full dose (melifix). Reading the pH levels the frontosa seem to need pH8-8.5 and the knifes pH6-8. My long winded question is... What do you all think about the knifes living with the frontosa? We are waiting to pick up and fix a 7ft which they would all move into. The 4ft also has 5 venustus, 1 old and wobbly maingano, 4 female red empress and a male tangerine peacock. The Knifes have been ok in the high 7.5-8.5 pH but what do you all think about the happiness of the frontosa and knifes together??? Thanks for any help and advice :)
Clarice Brough - 2015-03-04 This is a repeat to your comment under the Frontosa... but I'm still excited, so re-posting it here:)
Well I must say, I'm really excited about all your fish. I can tell you are a great aquarist:) Of course there's no guarantee, but I think they may be okay with each other (unless you find out you have a male Frontosa that decides to get territorial - but still, he may not be aggressive to existing tankmates!) You might be better off keeping the other African cichlids in the 4 foot, or at least have it available if they decide to get testy with the ghost knives and Frontosa. But I say try it, and be ready to adjust as needed!
Lyn - 2015-05-24 I don't know frontosa,but Google tells me they are a cichlid. If this is true, I have heard that cichlids can be quite aggressive, while knives are very calm and peaceful. I wouldn't risk it personally. Also, you would have to be VERY careful with your pH and carbonate hardness with the pH requirements being right on the brink for both species.
Rickey Stiles - 2015-05-23 i have recently got a black knife fish and was wondering if anyone noticed there's sleeping on its side or is mine defective lol thanks for reading
Lyn - 2015-05-24 I'm not an expert, but I have found my fish in odd positions at times, but not all the time. If your fish otherwise swims around and is eating then I would say that it's OK. Good luck. I'm absolutely hopeless but I've done OK with my two and they are now huge. I'm thinking that I'm going to have to buy yet another aquarium (I already have 5) just for them.
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