Black Ghost Knife Fish: Facts, Lifespan, Care, Feeding, & Breeding

Black ghost knife fish, also known as Apteronotus albifrons is an exotic freshwater fish pet. Experienced aquarium owners best handle it.

Despite the black ghost fish bioelectric traits it is still a great pet to have because it is docile, timid and a nocturnal bottom dwellers, which is good because it gives you the freedom to add tanks mates without the fear of predation.

Physical description

The black ghost knife fish is flat and long with a length of 10-22 inches from the nose to the tail. There are no abdominal fins nor dorsal ones too. All that is present for movement is its tail (anal fin).

Both the dorsal and abdominal fins are important for fishes to move properly as they are present in all fishes. In the case of the black ghost knife fish, the anal fin located in the tail section is well developed for easy swimming.  


The black ghost knife fish originates from south Americas. They can be found on the upper basin of the Amazon river which is over the territory of nations such as Bolivia, Peru, Brazil, and Columbia. The current of the rivers in such locations is slow, which is the preference of the black ghost knife fish.

Also, in such rivers, there is a lot of vegetation and hiding places for the black ghost knife fish to express its nocturnal traits.

you can say the habitat complements its behavior… 

The slow black waters is also a great example. It is perfect for a fish such as the black ghost knife fish. Since the current is slow, the fish will be able to swim peacefully and easily through with their only fin, that is the anal fin. The black ghost knife fish has no dorsal or abdominal fins; those would be useful in rivers with strong current.     


The ghost knife fish happens to be one of the most long-lived freshwater pet fish. Its average life span is between 10-12 years. In the right aquarium conditions and proper feeding, it can go further to the range of 15-16 years.

In the wild, the story is different; the rules are different. The black ghost knife fish has no scales, which makes them very sensitive to water pollutants and change in water conditions. On top of that, they can be preyed on by other bigger fishes. With all that out to get the ghost knife fish, it would be a miracle for it in the wild to reach the average lifespan range of 10-12 years.    

Ghost Knife Fish Facts

It uses bioelectrogenesis

There is an organ around its tail stalk. It irradiates low electrical pulses which are used for navigation in the dark waters. This comes in very handy for the ghost knife fish because its habitat has very low lightening which leads to poor eyesight.

 And again, the ghost knife fishes are nocturnal. They prefer to hunt and play about at night which is the perfect time to make use of their bio electrogenesis.

Here’s how it works…

The ghost knife fish will generate a low electric field around itself with the organ around its tail. This will allow the fish to have the ability to sense movement around it and also, to define objects or obstacles around it. Similar to a submarine which uses sonar systems to track movement and obstacles.

It uses one fin for movement

Naturally, for a fish to quickly it will need certain types of fins which are three in number, they include the dorsal, abdominal and anal fins. Possession of all three gives the fish the ability to swim quickly through both slow and fast currents.

The ghost knife fish possesses only one of those fins, and that is the anal fin. A fish with only one fin like the ghost knife fish can swim easily in slower waters. The waving motion of its small anal fin gives it the ability to move in any direction. 

It is extremely sensitive

There are no scales on the body of a ghost knife fish. This makes the fish vulnerable to water pollutants, diseases, and change in water conditions. It is best for the owner to make sure the proper water conditions for its tank is met and there are no diseased tank mates.

In order to handle the possibility of disease development in the tank, an external filter with UV sterilizers is recommended. It ensures your pet ghost knife fish lives a disease-free life.

They are shy

When introduced into a new community, it takes time before it becomes familiar. Even as the owner or food supplier, the ghost knife fish can treat you like a stranger until after a couple of days or week at worse.  

They can be good tank mates or bad tank mates

It depends mainly on their tank mates. Ghost knife fishes do well with larger and friendly species that swim on the upper stratus of the tank. They do not do well with slow swimming small fishes. The small fishes could end up being its prey.

They hunt at night

The ghost knife fish hides in the day time or In the presence of UV rays, but at night it hunts and feeds. When building an aquarium for a ghost knife fish, it should be a replica of its real habitat. Hiding places like caves, plants, and driftwood should be included. This way the ghost knife fish will be able to express its nocturnal traits and feel more at home.  

Tank conditions

Size of tank

Let’s begin with the size of the tank. An adult ghost knife fishes large, so it will need a large tank. The size of the tank should be at least 105 gallons in tank capacity. It can be larger, especially if a community is included.

It is preferable to keep a ghost knife fish alone in a tank due to its aggressive behavior when it comes to protecting its territory. To prevent this, there should be enough hiding places like caves, plants or driftwood for every territorial fish in the tank.

Water conditions

This is an essential part of setting up the aquarium. If this is done wrong, there is a high possibility of getting the ghost knife fish killed. The reason is that they do not have scales on their body. This leaves the ghost knife fish exposed to chemical and disease attack.

There are parameters to follow. They include the pH, temperature and hardness of the water.

The pH range of the water should be within 6.0 – 8.0. A little deviation from the range provided can be a too acidic or basic for the fish. It could lead to getting the ghost knife fish sick, due to its lack of protective scales.

The temperature of the water should be cool with a temperature range of 73-82 degrees Fahrenheit. Also, the hardness of the water should be within a range of 5-19 dGH. If the water movement in the tank is controllable, the speed should be moderate. This is so that the ghost knife fish will be able to swim easily around the tank.

What substrate should be used?

Its an option of either a sandy substrate or gravel. The gravel substrate should be fine so that the fish in the aquarium will not be injured.

Black ghost knife fish tank mates

The ghost knife fishes are docile and timid freshwater fishes. They are a great candidate for a community of fishes as long as the species are also docile and they are bigger than them. They include:

  • Oscars
  • Gourami
  • cyprinids
  • large Angelfish
  • discus
  • iridescent sharks  

The ghost knife fish in a community with these fishes mentioned earlier would be great, but still, care is essential. The ghost knife fish is very serious about protecting its territory, and it could very well lead to a clash with other fishes unless enough hiding places are provided.

The black ghost knife fish may be docile and timid, but it can live with small and slow-moving fishes. Such as neon guppy and tetra. They would be seen as food, as the ghost knife fish is omnivorous.  


The ghost knife fishes are discovered to be omnivores which means they feed on both plants and animals. There are varies of food in which the ghost knife fish can consume. They include live prey, worms, larvae, and flaked foods.

Fishes like the ghost knife fish are nocturnal. It means they hide in the day time and then feed during the night time. So the best time to feed them is at night. If the tank community consist of nocturnal fishes, it would be more convenient to feed. But in the case of a mixed community, the ghost knife fish can be trained to eat during the day like others.

How to feed

It is best to feed the ghost knife fish once a day when there is less light in the tank. They prefer to feed when there is less lighten.


In the wild, mating begins with Ghost knife fishes attracting each other with the use of electrical pulses in which they irradiate. The frequency of these pulses is different for both male and female.

Breeding of two adult ghost knife fishes will require a bigger tank because the size of an adult is 20-22inches. A separate large aquarium is usually dedicated to this situation.   

How to breed them?

Hobbyists have found it hard over the years, finally, they have made a breakthrough on how to do it successfully. Here are the following requirements:

  • Two matured black ghost knife fishes that are ready to mate. This is usually the hard part of breeding. They are very picky when it comes to choosing their mate. They choose with the use of their organs which enables them to generate electrical pulses. They will irradiate the pulses onto each other.
  • An aquarium with low lighting, low movement, and less noise. This is so there will be no distractions.
  • there should be giant pebbles, marbles or plant in the tank so that the laid eggs will not be touched by the parents who are likely to eat them.
  • the temperature of the water should be about 27 degrees Celsius. It is the optimal water temperature for effective breeding.
  • there should be continuous water changes every two or three days. The quantity between 25-50% should be changed. The reason for this constant changing of water is to create a feeling wet season in order to bolster the chances of breeding.   

Note: Changes in the water parameters of the mating tank are very important. It helps to increase the possibility of breeding two ghost knife fishes. When the water conditions are right, the fishes will be free of stress. The female ghost knife fish will be able to lay eggs comfortably for the male to fertilize.

After the eggs have been laid, remove the parents immediately form the tank, as they are likely to eat the eggs. This happens a lot in the wild. The parents are not attached to the younger ones.


So there you go. All the basics you need to know about the ghost knife fish. Overview:- They are docile, timid and nocturnal fishes with special abilities such as the act of generating electric fields for navigation and pulses for choosing a mate.

The care is a bit tricky but can still be done. They have no scales which makes them vulnerable. As long as the water conditions are perfect, the fish should have no problem. In addition to the right water conditions, there should be proper feeding (as they are omnivores). With those two sorted out, a ghost knife fish should be able to live up to 15/16years.

Breeding is another challenge. The process may hard, but it can be done. Just follow the requirements mentioned earlier on this post carefully.