Going across an aquarium and having your eyes simply awestruck by a fascinating creature present on this planet; yes, a Black Ghost Knife Fish is capable enough of doing that multiple times. This freshwater species has indeed fascinated many individuals, and we are now witnessing more popularity for this breed than any other fish. It is native to the Amazon River basin in South America, where it inhabits slow-moving streams, ponds, and canals.

The reason why this is given such a unique name is hidden beneath the belief of South American natives. According to it, those who depart from this world have their ghosts residing in these fishes. Isn’t this an interesting part on its own? Well, keep on reading till the end as it gets better.

For all we know, the black ghost fish is not an easy undertaking for any household. Comes the elegance of it, comes the personalized surroundings that are needed to be maintained at all costs. The guide below is a complete manual that educates, suggests, and pours information into every individual’s mind having or wanting to own this creature. Let’s dig in a little deeper.

All about the Species – Black Ghost Knife Fish

Quick Species Facts
Scientific Name Apteronotus Albifrons
Other Common Names Black Knife, Black Ghost, Apteronotid Eel
Family Apteronotidae
Origin South America
Lifespan 10-15 Years
Size 19 inches/ 50 centimeters 
Type Tropical Freshwater Fish


The charm of this scale-less fish has made it famous worldwide. Belonging to the Apteronotidae family, the fish got the ‘ghost’ in its name from the belief that many South Americans possess. The other part is dedicated to the look of it.

Being a peaceful fish, you can watch it freely, relaxing in your aquarium during the daytime. The night is when these try to locate food with their organ that responds to electrical receptors.

Speaking of senses, the black ghost can both emit and sense electrical signals in water. It would be best if you had a perfect balance in its surroundings to view the elegance of this fish.


The appearance is quite evident from the name given to this breed. How does it resemble a knife? It has long, thin parts that stick out of its face that look like hair. The rest of it looks like an eel with dark colors. The absence of caudal fins makes it look sleek as a knife. Two dorsal fins are present.

While its appearance is dreamy to the eyes, the absence of scales is indeed a loss of armor for this fish. The Black ghost knife fish does not have shiny scales like most fish do. Instead, they are rough to the touch, and this gives them a good grip when swimming in rivers and fast-moving water.

Besides having a blade-like structure, this creature has its nose containing a white strip followed by two white rings on its tail. The long, thin whip-like tail helps them move quickly through the water. Unlike colorful fishes, the body is completely black or merely shades of it and nothing else.


Watch this fish grow handsomely up to 50 centimeters or 20 odd inches. The jaw-dropping flat elongated body slowly turns into a blade-like structure. As mentioned above, the formation of a knife-like structure is possible due to the absence of scales.

To witness the handsome, fully grown length, you need to be very active towards its care. However, they do reach their maturity or full growth rapidly if everything falls right. You can observe a length of 15-20 centimeters in the first month alone.

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Pro Tip: Please pay attention to the surroundings and the black ghost knife fish’s diet. It is indeed the nutrition provided to it that affects growth. We highly recommend anything among bloodworms, shrimps, prawns, feeder fish, and frozen fish food.

Life Expectancy:

With a lifespan of 12 to 15 years, this big ghost knife fish gets subjected to sickness if the surroundings are not set in compatibility with the creature. Even a slight change in the pH levels can also affect health.

However, it is a decent period considering it is a freshwater species that is immensely prone to skin diseases mentioned below. Subsequently, regular training can develop or change its eating habits over the course of time. Continue reading the characteristics to know more.


When you set your eyes at the full-grown black knife fish, you are looking at a creature, unlike other multiple colored fishes. The absence of scales and caudal fins gives it a knife-like structure.

Though this fish has weak eyesight, an organ found in the tail allows it to locate food through electric signals. This fish species is nocturnal, hiding during the day inside burrows it digs in the stream bed. It is mostly during the night when these come out of their hiding spots and take a swim back and forth.

Some people think this fish looks scary because of its appearance, but it is actually a very gentle creature that only feeds on small fish and invertebrates. It uses its long snout to probe the substrate for prey.

The black ghost knifefish is a popular aquarium fish. It is a hardy fish that can tolerate a wide range of water conditions. Being an anti-social fish, you can watch them having their pleasure time alone.

One of the most unique characteristics of this fish is their ability to generate and sense electric fields, which they use for communication. This allows them to form complex social hierarchies. Continue to the next section if you wish to know about the tankmates and more.

Gender Identification: How to Identify Male and Female Black Ghost Fish?

It is hard to find whether the black ghost you are looking at is a male or a female due to the absence of clear identification marks. It revolves around the electric signals emitted by this fish.

Though it has been observed that female ghost knife fish usually emit signals of a higher frequency, this is still no conclusive evidence. However, one can look at the back of the head where there is a fat lump present in males. Another feature brought up was a tiny tummy-like belly in females.

Care for Black Ghost Knifefish

Quick Species Facts
Care Level Moderate
Social Temperament Non-Aggressive
Diet Carnivore (Meat, Live Fish)
Breeding Large Aquariums with Giant Marbles With Consistent Water Changes Needed

Diet and Feeding:

The black ghost usually feeds on meat and worms. Call it a treat in your own words. However, we have now shifted it to the omnivore section. The black ghost fish is not just a part of the carnivore category, as there were instances where they were found consuming flaked foods and common fish food.

Feeding means dinner at night for these creatures as they are more active at that time. That being said, you can train these to feed and be more active during the day, and here’s how you do it.

You need to put the food in at the exact hour every day. It can take days for these to know their food source. Up until then, they’d be very shy to come out of their spot during the day.

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Temperament & Social Behavior:

If the term ‘minding your own business’ needs an example, here is one. The black ghost usually stays within its own boundaries, completely non-aggressive until another one barges the border.

Hence, keeping a couple of them is not advised if you do not have the space large enough. For what’s worth it, if you are thinking of setting up a community tank, only then it becomes a matter of discussion.

They also respond to movements around the aquarium. You can sense it while you are putting the food in, and they come out once they see the sight as clear or non-harmful.


Since no perfect breeding measures are being formulated for this fish, there is plenty of confusing information one can go by. For breeding, you need to have a few things in order.

For starters, it requires a large aquarium, a temperature set around 27-degrees, and a grown couple ready to mate, which is not so easy to find. Fish owners have witnessed these fishes consuming their own offspring.

Therefore, you are advised to keep large pebbles and soft hiding toys such as grass handy where the parents cannot reach the eggs. The color of these eggs is yellow, and once you have a sight of them, you can separate the parents.

Black Ghost Knife Fish Care Guide

Common Diseases:

The absence of scales and caudal fins make the black ghost knife fish’s care one of the crucial aspects. As stated, a slight change in water’s temperature, hardness, pumping, and pressure, can pose a direct threat.

Fungal and parasite infections are the most common skin diseases attacking their body. That being said, Ich & Skin Flukes are commonly found in black ghosts. One clear indication is the visibility of white spots on the whole body. If you notice these, make sure you check the deviations in pH.

The best way to treat it would be to adjust the deviated parameter back to where it was. Whether it is the temperature, hardness, pH, or ammonium value, it has to get back to where it was set in the beginning.

Tank Recommendations

Quick Tank Facts
Minimum Size Minimum Capacity of 100 Gallons of Water For a Single Fish. For Multiple Black Ghosts- 150 Gallons of Water
Water Temperature 73 to 82 Fahrenheit
Water Hardness 5 to 19 dGH
PH Level 6.0 to 8.0

Ideal Tank Size:

This is where many fish owners commit a mistake. Not knowing the ideal size of the tank is a threat posed to this species. Speaking individually, the black knife fish requires 80 gallons of fresh water to roam freely.

The tank size usually depends on the number of creates you wish to see there. When it comes to petting a sole ghost fish, you need a tank containing at least 100 gallons of water, and for a couple, the range can go around 150 gallons. However, if you are thinking of setting up a community tank, you need to have tanks as big as fish breeders in Indonesia.

We recommend you go anywhere around 300-400 gallons depending on the size and number you have put in there.

Tank Setup, Décor, and Plants:

You get a bunch of opportunities when it comes to tank setup and décor. The black ghost knife fish will have high praises for you if you put in toys that create a few hiding spots in the tank. Since these remain shyly inactive during the day, they wish to stay behind the live grass or whatever toy there is.

Speaking of the grass, these go well with the live plants. Here you get a bunch of options unfolded. Further, make sure the décor revolves around a dark theme, and a medium bright light would do.

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Whatever it is, make sure you are keeping softness as the main priority. There is absolutely no space for sharp objects. Smooth marbles and pebbles work just fine.

Pro Tip: Make sure the toys or grass do not contain the whole of the tank. There should be enough space to roam.

Water Parameters:

If you wish to see your pet all dolled up till maturity and after that, you need to be cautious of water parameters. There are several of them to look up to. And unlike other species that may catch up with changes, this won’t do.

A slight change poses a threat of skin disease. Tie this thing up: The pH should range 6.0 to 8.0, hardness around 5-19 dGH, nitrate level below 20 ppm, temperature as mentioned above, and a flow that isn’t too hard on it. Keep a regular check on it. Monitor the water perfume once a while and keep it smooth.

Compatible Tankmates:

Speaking of tankmates, you have to have set the compatibility meter to ensure everything is safe and sound inside. It is best to keep a couple together only if you have plenty of space for both (150 gallons minimum).

Other than ghost knife fish, you have options such as catfish, rope fish, angelfish, mono sebae, and corydoras as tankmates. While keeping small fishes, you need to ensure the big ghost knife is on the smaller side in comparison to prevent it from preying on smaller ones.

Pro Tip: When it comes to prey, black ghost knife eating a goldfish is a common site witnessed by many. Hence, keeping tiny fishes away is strongly recommended when these grow in size.

Frequently Asked Questions

Can I Pet Other Fish With It?

Petting other fish species with the black ghost knife fish is not recommended for every breed you see, and only special breeds can swim peacefully with it (mentioned above). Besides, make sure you are not petting small or tiny creatures as they are most likely to fall prey to it.

Is the Black Ghost Shy?

Yes, the black knife fish is fairly shy in nature. They love to have hiding spots kept in their tanks, and you normally do not find them coming to corner where there is excessive movement of the presence of creatures. The aggressive side comes forward only if there is another being kept within a small range.

Where are Black Knife Fishes found?

The black ghost knife was first discovered in South America and parts of it. Although their entire population is not known, we do know they are distributed frequently and the lakes, ponds, and rivers in Bolivia, Brazil, Prague, and many others in South America. If you wish to see them up close, you either have to visit these places or pet these as many people do.

Can I Breed Black Ghost Knife Fish in Aquarium?

Breeding is most probably the hardest part when it comes to these creatures. Right from the beginning, it gets tough to find two black ghosts ready to maintain. Further, the conditions should be set in motion. And even if they mate, you need to have pebbles or spaces ready where eggs stay away from the parents since they can fall prey to the parents only. However, it is possible.

Can a slight change in water parameters harm this fish?

Due to the absence of scales and other protective fins, the black ghost knife fish falls prey to parasites, and other fungal infections commonly termed skin diseases. Yes, even a slight change can make them sick at times, and some notable features of sickness are white spots and flukes. However, you can adjust the water parameters back to the original to prevent further degradation of health.

Final Remarks

For all that we know, the black ghost is indeed a unique creature that turns every single eye that goes past the aquarium. Despite their size and potential for aggression, black ghost knife fish can make excellent additions to the home aquarium when properly cared for. They are active and curious fish that will add interest and excitement to any tank.

Creating a specific environment is indeed a requirement for every breed. So why not go one step ahead and get this jaw-dropping creature to grace up your fish tank. The black ghost can be a welcome addition to any community aquarium with proper setup and care.

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About the Author

Shelby Crosby

Shelby is a passionate fishkeeper who has been writing about fish for over 5 years. She is a pro aquarist and holds a BSc Honors Degree in Wildlife and Fisheries. She creates her own beautiful aquarium layouts and loves to share her knowledge of tropical fish with other hobbyists. Career Highlights: Has worked with several…

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