The Black Ghost Knife Fish – scientifically known as the Apteronotus albifrons – is a medium-sized beautiful aquarium fish species. It has a very unique appearance, and that is why a lot of fish keepers love to have it in their aquariums. It belongs to the ghost knifefish family and has a completely black appearance, that is why it is named the Black Ghost Knifefish. Fish from the ghost knifefish are known for their unique body shape, which resembles the shape of a knife if you are looking from the side. The Black Ghost Knife Fish is a freshwater fish species that are native to South America and is found in many rivers, including the Amazon, Paraguay, and Parana river basin.

This fish has many unique characteristics, for example, it sleeps during the day and becomes active during the night. Also, this fish species has electric organs that produce small amounts of electricity. Apart from being unique, and interesting, it is also one of the most popular aquarium fish that you can buy. But before buying it, you should know the proper care guidelines for this fish species. This is very important because this fish is not like most other fish species in your aquariums. For example, most aquarium fish species are usually smaller, but this one is not. There are also many other differences in the care of Black Ghost Knife Fish. Read the article below to know about taking care of the Black Ghost Knife Fish in your aquariums.

Basic Facts Table

LifespanUp to 15 years
Size20 inches
ColorsBlack, white spots on the tail
Freshwater or SaltwaterFreshwater
Care LevelIntermediate
CompatibilityFreshwater Aquariums and Fish Ponds

Tank Companions

Here is a list of the possible tank mates or tank companions of the Black Ghost Knife Fish.

  • Catfish
  • Cichlids
  • Angelfish
  • Discus Fish
  • Corydoras
  • Tetras
  • Rasboras
  • Guppies
  • Barbs
  • Oscar Fish
  • Rope Fish
  • Bichir Fish
  • Silver Dollar Fish
  • Electric Blue Acara

How To Select Tank Companions?

The Black Ghost Knife Fish is one of the largest aquarium fish species, and it is also an aggressive territorial fish. So, when you are selecting the tank mates for this species, you need to be very careful. You cannot select smaller species as they will be eaten by the large Black Ghost Knife Fish. Apart from this, there are other factors that you need to consider before selecting the tank mate for this fish. These factors include the size of the fish, age of Black Ghost Knife Fish, nature of the tank mates, and living conditions. You should test every tank mate that you want to select according to these parameters. If your tank mate follows these parameters, then it can be paired with the Black Ghost Knife Fish otherwise, it cannot be paired.

Keeping Black Ghost Knife Fish Together: It is highly recommended that you should not pair the Black Ghost Knife Fish with other fish from this genus or family. This is because all of them are large territorial and aggressive species. You will need very large tanks to keep them peacefully. Large tanks would allow them to establish territorial boundaries that are acceptable to the members of the tank. In smaller tanks, however, it would be a disaster because you will only witness fighting all the time. So, if you want to keep more than one Black Ghost Knife Fish in your tank, you should arrange a tank of more than 100 gallons capacity.

Size of Tank Mates: The size of tank mates for the Black Ghost Knife Fish is a very important factor that you need to consider. The Black Ghost Knife Fish can grow up to 20 inches in your aquarium, meaning that it would be able to eat most of the small fish species in your tank. So, you cannot pair them with any fish species that is small. You can however pair them with some small species when your Black Ghost Knife Fish is growing and has not reached the mature size. For example, you can put tetras in the tank of Black Ghost Knife Fish that are two to three years old and are about 8 to 10 inches long. Once the Black Ghost Knife Fish reaches mature size (longer than 15 inches) it will become highly aggressive towards smaller fish in your tank and will try to eat them. So, you should remove any small members before that.

Living Conditions of Tank Mates: Another very important factor to consider is the living conditions that the tank mates need. It is important because if the living conditions of your tank mates do not match with the living conditions and parameters of Black Ghost Knife Fish, you would not be able to pair them. For example, the Black Ghost Knife Fish is a freshwater fish and lives in freshwater aquariums. You cannot pair it with the fish species from marine aquariums or brackish water aquariums. It would kill the tank mates because the living conditions of Black Ghost Knife Fish would be hostile for them. For that reason, you need to check the parameters and living conditions of your tank mates and match them with the Black Ghost Knife Fish. If everything checks out, you can pair them, otherwise, you will have to look for other options.

Temperament or Behavior of Tank Mates: It is also important to consider the temperament and behavior of the tank mate that you have selected. As you know, the Black Ghost Knife Fish is an aggressive and territorial fish that does not like its territory to be invaded. So, if you paired them with a fish species that is also territorial and aggressive, it would be disastrous. Both aggressive fish would invade each other’s territory, attack, and fight all the time. This would make your tank look hostile, and can cause stress in both of the tank mates, resulting in bad health conditions, injuries, and death. You can prevent all of this by introducing a peaceful fish species in the aquarium Black Ghost Knife Fish. A peaceful fish would avoid fights and it would make your aquarium look peaceful.

Species Overview

The Black Ghost Knife Fish is a unique-looking fish species that you can have in your aquarium. Its key characteristics include the black appearance, white rings on the tail, and knife-like body shape. It belongs to the family of fish known as the ghost knifefish or Apteronotidae. Fish from this family are known for their unique appearance. It is one of the most popular fish from this family that is commonly seen in various aquariums worldwide. This fish has multiple common names. These common names include Apteronotidae Eel (based on the scientific name of its family and eel-like long appearance), and Black Ghost or Black Knife.

You can buy them from online stores, and local aquarium fish trading markets. It is one of the most aggressive and largest fish species that you can buy for your aquarium. This fish is also highly territorial, that is why fish keepers advise keeping them alone in a tank where they can establish their territory. Also, the aggression of this species makes it a very difficult fish species to breed in captivity, unless you have a very large tank or pond. It is a very important fish species in many cultures, especially in the Amazon tribes. According to Amazonian tribe legends, this fish species contains the souls of dead people and that is why it was named the ghost knifefish.

But this name is not associated with one species, the whole family of these fish is called the ghost knifefish. The Black Ghost Knife Fish is a fish that becomes active during the night and stays dormant during the day. It is a type of behavior that makes this species a nocturnal fish. As you know that there is no light during the night in the water. This fish has many adaptations that allow it to navigate through the water during the night. It uses a specific set of organs that produce an electric current. It uses that electric current for navigation during the night. It allows the fish to know its location in the water, the location of its prey, and its territory.

The Black Ghost Knife Fish is one of those fish species that can live for a long time in your aquarium. With minimum care, their lifespan can range between 8 to 12 years. Meanwhile, the average lifespan of this fish is up to 15 years if you provide them excellent care. So, if you want these fish to live for a long time in your aquarium, you should provide them excellent care, and living conditions. Both males and females in this species have electrogenesis and electrolocation abilities. But the frequency of electric signals sent by females is greater than the male ones.


Black Ghost Knife Fish has one of the most beautiful, unique, and interesting-looking appearances. The whole body of this fish is covered with black color. Meanwhile, the tail contains two rings of white color. In the early days of its lifespan, the black color is not very dark but as this fish ages, the black color becomes darker. It has an elongated body shape (like an eel or knife). The mouth of this fish is in the middle of its face, which allows the fish to quickly capture any swimming prey it can find in the water.

Black color helps this fish hide in the darkness during the night. It protects it from being captured by the larger fish in their natural habitat. Fins in this species are ray-shaped. This fish also lacks dorsal fins. The size of a healthy member of this species can be 20 inches. It is also a scaleless fish species, so you will not see any color variations when light falls on their bodies.


The Black Ghost Knife Fish is native to South American rivers, including Paraguay, Parana, and Amazon river basin areas. This fish has multiple adaptations that allow it to live in the dark forest-covered waters of these rivers. Most fish in this region avoid swimming in the deep water, but this fish can easily swim against the fast-moving water currents. That is why it is mostly found in the middle of the river where the water is about 6 meters or deeper. It is found in many countries in South America including Venezuela, Brazil, Argentina, and Paraguay. Most of them are found in Paraguay along the Paraguay River and Parana River, but some are also found in areas outside these rivers. Some of them are found in the Amazon river basin, but here the concentration of these fish is low.

Natural Habitat

The Black Ghost Knife Fish lives in freshwater habitats such as rivers. It is found in deep areas of the river where there is a low concentration of other fish species. It visits the sides of the river during the night to prey on small crustaceans, fish, worms, and shrimps. This fish has adapted to no light conditions. For example, it uses electrogenesis as a location and navigation tool in the deep waters where there is low light. Its natural habitat has low light conditions, neutral pH, a higher level of flow, minimal hardness, and plenty of food. If you are creating a habitat for this fish, you should follow the same pattern. Provide them a slightly cold, neutral, and soft freshwater habitat so that they can live and thrive.

Black Ghost Knife Fish Lifespan

The lifespan of Black Ghost Knife Fish depends on the care and tank size that you are providing them. For example, if your tank is large enough to support their growth, and provide them a space to explore and you are providing them excellent care, the Black Ghost Knife Fish will live for up to 15 years. But if your tank size is small and your care is poor, your fish would only live for 8 to 10 years. You should learn about the proper care guidelines and size of their tank to extend their lifespan in your tank.

Habitat and Tank Conditions

If you want your Black Ghost Knife Fish to stay healthy and have a longer lifespan, you should provide them with an excellent tank, and habitat conditions and take good care of them. First, we need to take a look at what type of habitat or tank conditions this fish needs. This knowledge will help in the selection of the right size of tank and provide them with better living conditions. There are also some parameters that you need to maintain to make sure that your fish can live in your tank. Below is the list of parameters, habitat, and tank conditions that you need to know about.

Tank Size

The first thing that you need to know about when creating a tank for the Black Ghost Knife Fish, is the size of your tank. As you know, the Black Ghost Knife Fish is one of the largest tank fish, you need a bigger container or tank for them. You cannot use a smaller tank or a low-capacity tank. You will have to select a tank that is tall, deep, and also has more water capacity. This is a highly territorial and aggressive fish species. You need a large tank so that it can establish its territory in the tank. In smaller tanks, establishing the territory will be difficult in the presence of others. fish. Here are some factors that you need to consider while selecting the size of the tank for your Black Ghost Knife Fish.

  • Age and size Black Ghost Knife Fish is an important factor to consider. If your Black Ghost Knife Fish is small and young, you can keep it in a small tank or even a community tank. But if your Black Ghost Knife Fish is large and has reached maturity, you will need a large and separate tank.
  • You will need to select a tank according to the fish per gallon ratio, and the number of fish that you want in that tank. According to expert fish keepers, you need at least a 50+ gallons tank to contain one Black Ghost Knife Fish. but if you want to put other fish in this tank, you will need at least a 75 to 100 gallons tank.
  • If you are building a community tank where you want to pair other fish species with Black Ghost Knife Fish, you will need an even larger tank. It depends on how many fish you would keep in that tank. For example, if you are keeping five to ten fish, you will need a 75 to 100 gallons tank. But if you want to keep more fish, you will need an even bigger fish tank.

Keep these factors in mind when selecting a new tank for the Black Ghost Knife Fish so that your fish gets the type of environment it needs. The most appropriately sized tank that is used for this fish is a 100 gallon tall, and long tank.

Tank Setup

Selecting the tank is the first step, after that, you need to decorate that tank in a way that looks like the natural habitat of Black Ghost Knife Fish. You can do that by putting an appropriate amount of gravel in the bottom of your tank. Two to three-inch layers of gravel, stones, and pebbles are enough for this tank. You should know that this fish species spends a lot of its time in the bottom of the tank, and you need to make sure that there are no sharp-edged stones that can hurt your fish.

After that, you can start planting some aquatic plants in your aquarium. These aquatic plants provide a lot of benefits including filtering the carbon and adding oxygen to your tank. They also serve as a food source for some of the tank members. Many fish species lay their eggs on the leaves of these plants, which helps them breed. For that purpose, selecting an appropriate plant is important. Some of the commonly used plants in the aquarium of Black Ghost Knife Fish include java ferns and amazon swords.

Once you are done with that, you will need to put some decorations in your tank. These decorations will make your tank look beautiful, and would also make it interesting for the fish to explore. You can put caves, rocks, and driftwood in the tank. Apart from this, you will also need to add a filtration system, aquarium lights, and a heater. The filtration system provides flow, and filters the water, meanwhile lights help you create day and night scenarios, and the heater maintains the temperature of your tank. 

Water Conditions/Parameters

Here is the list of water conditions or parameters that you need to maintain in the tank of Black Ghost Knife Fish.

  • Temperature between 73°F to 80°F.
  • pH levels between 6.5 to 8.
  • Hardness between 0 to 10 KH.

From this, you can see that these parameters are flexible. It is better to maintain these parameters within the given ranges. You can maintain temperature using a water heater, ice cubes in summer, and pH by using driftwood and calcium carbonate or bicarbonates. If you maintain these parameters correctly and within the given ranges, your fish would live a long and healthy life. 

Water Source

For the tank of Black Ghost Knife Fish, you can use water from multiple resources, including rivers, freshwater streams, lakes, and local reservoirs. You can also use your tap water but you will have to test your water for contaminants. This is an important step because it helps you prevent diseases and the death of your fish in the tank. There is also special aquarium water available for fish tanks. You can also buy that and use that. But if you want to use your tap water, you will have to test it and then filter it using an RO filtration system. RO or reverse osmosis filtration system would completely clean your water and would make it usable for the fish tanks.

Behavior and Temperament

The Black Ghost Knife Fish is known as an aggressive, hyperactive, territorial, and less social fish species. It likes to occupy a specific part of your large tank and would stick to it. But if the tank is small, it would occupy the whole tank and would kill any competitors in the tank. For that purpose, it is advised that you should use a large tank. The aggression of this fish can only be controlled if it is being properly fed, and is kept with peaceful fish species. It is a hyperactive fish species, meaning that it is a fast swimmer. But it is also a nocturnal species, and it only becomes active during the night. Meanwhile, it would lay dormant during the whole day. You can use aquarium lights to depict the day and night cycle indoors.

Breeding Black Ghost Knife Fish

It is one of those species that are hard to breed. The main reason behind this difficulty inbreeding is that it sees other Black Ghost Knife Fish as a competitor. It would attack other members of its family, making breeding virtually impossible in smaller tanks.  Those who still want to try breeding would need to make specific preparations before starting the breeding process. Here is how you can breed the Black Ghost Knife Fish.

  • Start by creating a large breeding tank of 100+ gallons or use a large size fish pond. Put one male and one female in your breeding tank.
  • Plant a large number of aquatic plants in that aquarium or fish pond and create a lot of hiding spots.
  • Use two large pipes for flooding the tank and draining it at the same time.
  • Allow your fish to spawn in the tank, keep feeding them with a high protein diet. Your fish would spawn, and females would lay eggs.
  • Eggs will turn into small fry after a few weeks, fry should be extracted from the tank and protected from the parents and other members of the breeding tank.

Creating this type of setup is only possible if you are breeding this fish at a commercial level. Otherwise, you will be spending too much money on a very low chance of success. For that reason, many fish keepers advise against doing it at home. Also, you can buy a new Black Ghost Knife Fish at a low price, meanwhile, creating a tank for breeding them would cost you hundreds of dollars.

Diet of Black Ghost Knife Fish

The diet of Black Ghost Knife Fish is carnivorous, it only feeds on the living insects, small fish, crustaceans, shrimps, and bloodworms. You can feed it easily with a protein-rich diet that includes both live and frozen foods. Try to provide them with a balanced amount of food, proportionate to their size. It is important to feed them once every day. Bad food or wrong feeding habits can create multiple health issues for the fish. For that reason, try to feed them healthy food.

Diseases of Black Ghost Knife Fish

Here is a list of the possible diseases of Black Ghost Knife Fish.

  • Ich: It is a common fish disease that attacks this fish. It causes white spots to form on the skin. It can be treated, but it is a highly contagious disease. Meaning that you will have to treat your fish and will also have to sterilize the whole aquarium.
  • Skin Infections: This fish has no scales, which can cause skin infections. For example, if there are any type of scratches on the skin of this fish or any injuries, these can lead to bacterial and parasitic infections that can deteriorate the health of your fish. You can prevent this by eliminating anything that contains sharp edges. Infections however are treated using antibiotics.

What is the Ideal Size For The Tank?

The Black Ghost Knife Fish is very large, that is why you need a large tank to contain them. Most fish keepers recommended selecting a 100 gallons capacity tank for this fish.

Is Black Ghost Knife Fish Saltwater or Freshwater Species?

The Black Ghost Knife Fish is a freshwater fish species that live in tropical regions in South America.

Is Black Ghost Knife Fish schooling species or not?

No, it is not a schooling or social fish species. It is an aggressive territorial fish that does not like its territory being invaded. Also, it is mostly kept alone in tanks, that is why there isn’t much information on this topic.

Conclusion – Is Black Ghost Knife Fish Suitable For Your Aquarium?

The Black Ghost Knife Fish is one of the most beautiful, popular, and mesmerizing fish species that you can get for your aquarium. It has a unique shape and color. This fish also has some unique features that are not seen in many aquarium fish, such as electrogenesis and communication using electric signals. Their care is intermediate and they need more space in the tank. But if you are a fish keeper, you must have this beautiful and unique fish in your tank. It would amaze you with its beauty and swimming habits. Based on these arguments, it can be said that yes, it is a suitable fish for your aquarium.


Question: Do Black Ghost Knife Fish Jump?

Answer: Sometimes this fish can try to jump out of the aquarium. To prevent this from happening, you will have to cover the tank with the help of a lid. This type of behavior is not very common and is only seen in those individuals that are under stress or suffering from diseases. 

Question: How to select tank mates for Black Ghost Knife Fish?

Answer: You should consider selecting a mostly peaceful, large fish species for the tank mate of Black Ghost Knife Fish. This would help you prevent the Black Ghost Knife Fish from eating the tank mates or attacking them.

Question: Do Black Ghost Knife Fish eat shrimps?

Answer: Yes, the Black Ghost Knife Fish is a carnivorous fish species that eat shrimps.

Leave a Reply