Black Ghost Knife Fish – A Complete Guide (Care, Diet, Facts)

Black Ghost Knife fish are a popular fish for a reason. Their elegance and physical beauty draw in hobbyist around the world. South American tribes tell Ghost stories around these fish and electro genesis bases around these same fish.

So, to say the least it makes a great ice breaker.

People say there is a specific rule of nature that everything must meet; and some say this fish is an exception to that rule.

With no scales, fins, or a traditional tail this fish isn’t like anything you’ve ever seen before. Their tails look more similar to a rod than a tail.



This fish is one of the most popular fish of its breed. Originally given the scientific names of the name of Gymnotus Albifrons and Apteronotus Passan.

Although, as time went on and more research was done on this fish the names were changed to the single name of Apteronotus Albifrons. If you go to purchase one it has multiple names in that category as well.

You may find it with the name Black Ghost Knife Fish or Apteronotidae Eel of just as the Black Knife Fish.

Ancient South American Ancestors told a story of the Black Ghost Knife Fish.

They believed that the spirits of the dead within the Amorim jungle would live within these fish. Hints why they call them the Black “Ghost” Knife Fish. These nocturnal fish have a special power they use to hunt during the dark hours.

Using a thing called Electrolocation; which is a way of sensing life by waves of electricity that is sent through the water. With the proper care and habitat this fish can live up to 15 years in a ranked environment.

Behavior of the Knife Fish

These tropical freshwater fish are native to South America. These fish are a nocturnal animal meaning you will see them do all their moving during dark hours rather than during bright days.

Being a night hunter, these fish never developed a strong sense of sight. Rather they use their electric abilities to do everything. Being a shy fish, they prefer their own space and no socialization.

Black Ghost Knife Fish do not do well with others of its kind. They are known to become aggressive and troublesome in this situation. As they settle down, they will find their hiding spots for say time and will get into a healthy routine.


The Knife Fish are a solid black specimen with two white halos on its tail. Along with one white stripe that runs from its nose down its back. Oddly enough, it’s the perfect shape of a butcher knife. Having few finds and no scales.

Reaching a whopping 20 inches long full grown with an anal fin running from the abdomen to the tail. Gives this fish a different swimming pattern than most fish. As mentioned before this fish has not the first scale; with that being said these fish are very sensitive to water conditions.

Scales give fish this extra layer of security and protection. So, being a fish without scales maximizes the chances for reacting poorly to water conditions or getting a life-threatening disease. One talent these fish gave is the ability to send out and take in electric signals.

This ability comes from an organ they carry within their tail. They use this sense to communicate, Hunt, and other unknown things. It can be nearly impossible to sex out this breed of fish. Although, it is said that females produce a higher frequency of electricity than males.

Habitat and Tank Conditions

These fish are found along the Amazon River and its cut offs. From waterways of Venezuela all the way down to Peru. The Black Ghost Knife Fish flourish in these waterways because of the rocks and caves available for hiding throughout the day.

The Amazon River and run offs are full of vegetation that aerates, provides hiding, and blocks from the sub light. Living inside of murky water with little to no visibility.

Having an extremely poor sense of sight these fish live inside murky water to ensure that predators have no sight advantage on them. The Knife Fish perfers medium strength currents.

Tank Setup

Being more of a shy passive fish, Black Ghost Knife Fish need plenty of places to hide. This will give them a sense of security they need. They prefer some sort of smooth rocks and plants as this is what they have in the wild.

Being a scale, less fish Knife fish can be injured easily if you place the wrong decorations or substrate within the tank. Choosing a form of fine substrate (rock or sand). The tank shouldn’t have any form of strong lighting. As these are nocturnal fish and they do not like the light.

It’s best to mimic the water currents that would be found in their natural habitat. Which means that this aquarium will need to have medium to high current levels. In the wild these fish aren’t found in great water conditions; which means they aren’t subject to a whole lot of special water specifications.

Although, they do best in waters that are between the temperature of 73°F and 82°F. They prefer the Ph to stay between 6 and 8; along with a water hardness between the numbers 5-19dGh. Black Ghost Knife Fish are freshwater fish and have no tolerance to salty water conditions.

This fish has been known to hide inside tubing or water filters. Be sure to keep this in mind and set up the tank in a way that covers or contains the system to where the Knife Fish cannot make their way inside and surprise you.

As mentioned before these fish have no protective layer and are more prone to infections and illness.

So, you may want to purchase a form of UV sterilizer to keep this from happening to your fish.

It’s better to be safe than sorry.

Aquarium Size Specifications

Being a large fish, they need plenty of room to maneuver and roam. What that being said they need at least a 100-gallon tank.

Fish per gallon

This fish is not an aggressive fish. For the most part they do their thing and keep away from other fish.

Although, they can and will become aggressive if there isn’t enough space for these fish to feel safe and comfortable. They will begin by taking out the smallest and least aggressive fish.

They do this to create more space, not to play or kill for fun. If you decide you want to keep multiple Black Ghost Knife Fish together you will need at least 80 gallons per fish.

Tank Mates

This fish was given the label of semi aggressive due to the fact they will stand their ground or kill other fish. Although, they only do this with reasoning. Black Ghost Knife Fish don’t kill for fun or game. Being a shy fish, they rather hide and keep to themselves then have to be in any type of predicament. Which makes they a perfect candidate for a community tank.

The ideal tank mates are fish of equal temperaments and similar sizing. If you have a small tank mates they may be looked at as food due to this fish being a carnivore. Nonaggressive members of the Cichlid family, or Catfish are great examples of the type of tank mates suitable for the Black a Ghost Knife Fish.

They will become aggressive if you have too many fish within one space or if they are limited to hiding places. Without hiding places these fish feel insecure and threatened. Which will cause them to thrash out and kill. These fish also do not accompany well with fish of its own bloodline or similar bloodlines.

A full-grown Knife Fish should not be ranked with any fish smaller than 6 inches.

A juvenile Knife Fish may be kept with smaller fish but must be relocated once the over grow the smaller fish by a couple inches. Keeping these fish with other aggressive fish may trigger them to be aggressive. So, it’s best to be kept with more peaceful fish.

Having Multiples

As mentioned, before it’s best not to keep two of their species together as they become aggressive and territorial. Although, in situations such as a large tank giving each fish at least 80 gallons it is possible to have little to no trouble having more than one.


These fish are not the fish for beginners. The reasoning behind this is that they are a challenging fish to raise due to temperament issues and their lack of fins and scales.

Water conditions can throw weed flag if it has to many chemicals so it’s best if you purchase some form of UV Sterilizer. These fish are highly allergic to copper-based medicines. Accidentally feeding this to

them will cause death in more circumstances.

Black Ghost Knife Fish are prone to diseases such as Ich. It’s easy to tell if the fish is coming down with this sickness. The fish will begin rubbing themselves on decorations, the side of the tank, and on anything it possibly can to itch itself. The only good thing is that this is a curable sickness and it can be cured if caught in time.

Raise the temperature to 82°F if any sickness is found. This will prevent reproduction and growth of the disease. Keeping it from spreading throughout your tank like wildfire. These fish are commercially bred in Indonesia to ensure population control for the South American native.

When buying online it’s easy to distinguish wild from commercially raised fish. If it’s a single fish over 5 inches, it probably is a wild caught fish. No matter the environment it came from its best to quarantine your new fish to ensure its free of sickness and disease that may spread throughout your tank. If you don’t be cautious you can end up with a tank full of dead or sick fish.


Black Ghost Knife Fish feed on meat. Making them carnivores. Feeding on anything from insects, larvae, fry, and small fish. These fish don’t like being fed food pellets or flakes. Although, with some adjusting they can and will eat these before starving.

Due to the fact that these fish have not had to adapt they tend to overlook dry food. They prefer fresh or frozen prey to feed on. They enjoy shrimp, bloodworms, and black worms, crickets, krill, and prawns.

Be sure that no matter the food you choose to feed that it provides a healthy and balanced diet. This will keep their immune systems up. They should be fed multiple times a day. Be sure to turn off the light during feedings because these fish are nocturnal so it may take you mocking night in order for them to come out and eat.

In the beginning it’s normal for a Black Ghost Fish to hide and not eat. Being a shy specimen, they take time to warm up to a new environment. Some hobbyists have managed to feed their Black Ghost Knife Fish by hand. While it is rewarding it does take a lot of time to gain trust and teach the fish.


Black Ghost Knife Fish are a popular choice for tanks in the recent years. With a unique swimming style that can put anyone in awe. These fish are very kind and friendly once they are comfortable and happy. Much like eels these fish sense their prey and communicate through electro-sensory.

Due to a missing layer of protection Black Ghosts are sensitive fish and are prone to sickness. Being an electro-sensory Fish, it can be hard for these fish to dictate where dry food may be. Being a nocturnal fish, it will do most of its moving during bedtime; and more it’s sleeping when you’re awake. Just be sure to check on it as often as you do the day fish.

Over the years people have been feeding Black Ghost out of their bare hands. These fish are a perfect choice for any experienced person. This is not a beginner fish due to size and temperament issues.




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