Black Ghost Knife Fish Ultimate Care Guide 301

Black ghost knife fish are well-known for their attractive appearance and have attracted a lot of attention from aquarists. However, we have found that there is a lot of misinformation about this species.

Black ghost knife fish care can be more difficult than for many other freshwater species. This is due to their unique needs and size.

We’ve never seen a black ghost knife fish like it. It’s hard to forget if you get one in person!

This guide will tell you everything you need about these fish. You’ll be able to identify their preferred tank mates, diet, size, and other details by the end of this guide.

Black Ghost Knifefish Facts & Overview

Care Level:Intermediate
Color Form:White and Black
Lifespan:10 to 15 years
Size:20 inches
Minimum Size of Tank:100 gallons
Tank Set-Up:Tropical-freshwater
Compatibility:Medium size peaceful fish

One of the most well-known Knifefish is the Black Ghost Knife Fish. It was previously known as Gymnotus albifrons or Apteronotus pasan. Today, this fish is called Apteronotus albifrons.

It is also known as the Apteronotidae Eel and Black Knife.

South American tribes tell a fascinating story about the fish. The tribes living in the Amazonian jungle believe that these fish are home to the souls of the deceased.

These stories are the basis for the common name Ghost Knifefish.

These fish are mostly nocturnal and use electrolocation for navigation in dark waters.


Under good care, a black ghost knife fish can live for around 10 years. In some cases, it can live up to 15 years!

Their lifespan is largely determined by their overall care, both before and after they are purchased. Genetics also plays a major role. You can do the best with what you can control and this fish will likely live for a long time.


When fully grown, the average black ghost knife fish is between 18 and 20 inches. This information is often misunderstood. Many potential owners think they are smaller than they actually are.


It can be purchased online or at pet shops for as low as $7.

Behavior and Temperament

Black ghost knife fish are generally independent and prefer to take care of their own affairs. They are active fish and prefer to be left alone.

They are used to swimming in and around hiding spots near the substrate, looking for food. Anything else will cause them extra stress.

They also have an aggressive side.

They will only show this behavior if they are around other black ghost knife fish. It doesn’t mean that you can’t have more than one fish in the same tank.

These fish will not be aggressive towards one another as long as they have enough space. They can become very grumpy if they are forced to share space with others.

Black Ghost Knife Fish is a tropical freshwater fish that hails from South America. These are nocturnal fish who are active mostly at night and sleep during the day.

They are active mostly at night and have poor eyesight so they hunt and communicate with an electric field.

They are shy and prefer to be alone. However, they can become aggressive if they are surrounded by other Knifefish. Once they have settled into their new environment, they will swim close to the foliage or substrate and other plants.


The Black Ghost Knife Fish is, as its name implies, entirely black, with two white rings at its tail and a white stripe that runs along its back.

It is, unsurprisingly, shaped like a knife. There are no caudal nor dorsal fins.

Their bodies are flat and long, measuring up to 20 inches when fully grown. From the belly to the tail, the anal fin runs along the body. This gives it a graceful swimming style.

This Knifefish species does not have scales. This fish is extremely sensitive to water conditions, infections, and lacks any protection provided by scales.

Black Ghost Knifefish is able to both emit as well as receive electric signals. An organ located in the tail produces electricity. These cells are found on the skin of fish and serve two purposes: communication and electrolocation.

It is fascinating to see the differences in electrogenesis between the sexes. Although there is no obvious dimorphism between the sexes, it has been shown that males emit higher frequencies than female.

Habitat and Tank Conditions

The Black Ghost Knife Fish can be found in the Amazon River, its tributaries, and the freshwater basins of Peru.

These waters are rich in vegetation and offer many hiding spots. Low lighting and moderate currents make the waters murky.

Water would also be relatively neutral in pH and warm.

They would have a soft sand substrate that won’t scratch. This is crucial because they have not scales.

These tropical freshwater habitats house a variety of insects that provide ample insect larvae for Black ghost knife fish to eat.

Black ghost Knife fish in captivity need an environment that is as close to their natural environment as possible. It is easy to do this. We will show you how.

Tank setup

They are shy fish and appreciate hiding spots. They love smooth rocks and plants in their aquariums.

This fish is not scaleless so it needs a good substrate. You can use fine gravel or sand to keep them safe. Low lighting and a moderate to strong water current are required for the tank.

They are very tolerant of a variety of water conditions because the water they drink is murky. The best water parameters for fish are a temperature range of 73.0-82.0degF, a pH range of 6.0-88.0, and hardness between 5-19 dGH.

Black Ghost Knife fish is a freshwater species that can tolerate brackish conditions.

Many hobbyists discover their fish hidden in canister filters or tubing. To avoid any surprises, make sure you use pre-filters and cover any inlet tubes when setting up your tank.

A UV sterilizer is an excellent purchase as they are susceptible to infection and scaleless fish.

Which size aquarium do they need?

Black Ghost Knife Fish is a large fish that requires a large aquarium with at least 100 gallons.

How many can be kept per gallon?

They aren’t aggressive towards other tank mates, such as peaceful Cichlids. However, they can become aggressive when they share small spaces with similar or identical species.

You will need at least 80 gallons for each fish if you keep them together.

Tank Mates

They are great for community aquariums, even though they are semi-aggressive fish.

This fish will be at home in a peaceful community of fish that are similar in sizes, such as calm Cichlids and peaceful Catfish.

Black Ghost Knifefish can become aggressive when they have to live in small spaces or lack hiding places.

They can also be quite boisterous when they are kept with other members of the same or similar species.

You should ensure that any tank mates you add are at a minimum of 6 inches in diameter and very peaceful.

You can create the perfect community with peaceful Catfish, Angelfish, and large peaceful Cichlids.

Corydoras make great aquarium companions and help to keep it clean.

Of course, tankmates must have the same preferences in terms of water conditions. This excludes species such as Goldfish, which prefer cooler water.

You might be able to keep your Black ghost knife fish growing with smaller fish like Tetras and Guppies, Barbs, Rasboras, or barb.

As your Black Ghost’s favorite food, small crustaceans and gastropods such as snails and shrimps aren’t a good choice. They are most likely to be consumed at night.

These fish should not be kept with aggressive fish or small fish that can be considered food.

Black Ghost Knife Fish and the Keeper of the Heart

If you have a large enough tank to allow them to establish their territory, keeping Black Ghost Knifefish together may not be a good idea.

Take care

Black Ghost Knife Fish should be kept by more experienced aquarists because they can be difficult to keep.

This fish is not able to scale and is very sensitive to chemicals and diseases in the water. You might consider purchasing a UV sterilizer.

Keep in mind that copper-based medicine can be very toxic for these fish.

Knifefish can develop skin flukes, such as Ich Disease. The fish may scratch and itch around the tank. However, if they are given the right treatment, they will recover quickly. If you suspect an infection, raise the temperature to 86°F. Parasite growth and reproduction are disrupted by higher temperatures.

They are commercially raised in Indonesia, which is great for the wild populations in South America.

Consider the size of the animal before you buy it. If the individual is larger than 5 inches, it is likely that it was wild.

Parasites and other diseases can be carried by wild animals. To ensure that no unwelcome organisms get into your aquarium, make sure they are placed in quarantine.

Recommendations for Food & Diet

Black Ghost Knife Fish is a carnivorous species. They feed on small fish and worms as well as larvae of insects.

This won’t affect the tank and your fish should be fed fresh or frozen food like brine shrimps, bloodworms, or blackworms.

You can also feed them tubifex worms or krill. However, they might not be used to pellets and flakes as quickly as you would like.

They are more inclined to avoid dry foods.

To ensure your fish have a healthy immune system, it is essential to provide a diverse and balanced diet.

You should feed them enough food daily to keep them satisfied for a few minutes. They are night-sleepers and should be fed at night or in the evening.

They might struggle to eat at first. Black Ghosts can be shy at first and may take some time to get out of hiding.

Hobbyists can also feed their pets by themselves. You might want to give this a try but it will take patience. Although it can be tedious to train your fish properly, it is very rewarding.


Black Ghost Knife Fish should not be kept in tanks. Some hobbyists claim they have successfully bred them, but the methods are often disputed.

They have been successfully bred by some commercial fisheries in Indonesia. They are very secretive about their successes, so it remains a mystery.

These are the most popular factors that encourage breeding:

  • Large tanks (at minimum 100 gallons)
  • Aquarium with densely planted plants
  • There are many hiding spots
  • Drainage and flooding the tank

Eggs are laid in caves or other protected areas. They are usually yellow with a diameter of 0.08 inches. It takes just 3 days to hatch their eggs.

Once eggs are laid, parents should be kept separate from their children. The eggs can be eaten by the parents in the wild; they don’t seem to have strong parental instincts.

After the fry is released, they need to be given small food. These foods could include infusoria or baby brine shrimp and/or flake food.

Many aquarists never reach the point of raising Black Ghost Knife fry. If you do manage to achieve it, please share your experience with others to help them and shed some light on the mystery.

What’s next?

Black ghost knife fish care can be very rewarding if you are up for the challenge. These fish are a joy to watch swim around in the aquarium.

Now that you know how much effort it takes to acquire this species, you can decide if they are right for you.

When considering purchasing a fish, we encourage potential owners to be honest. It’s not a good idea to buy a fish that you don’t know how to care for.

We are here to help you if you have any questions about black-ghost knife fish. We aim to help and encourage as many aquarists as possible.


Black ghost knife fish are very common. They have a beautiful swimming style and can be friendly once they’re settled in the tank.

Knife fish, like most eels, has an electro-sensory device that is used to detect and communicate location.

These fish are sensitive to disease and can be picky eaters so it is important that you have some experience before you start keeping them.

This fish is active at night and is nocturnal. They are carnivores that eat worms, brine shrimps, and insects.

Aquarists have been able to train their Knife Fish to eat with their hands over the years.

Are you a Black Ghost Knife Fish owner? Please share your experiences in the comments below.


Dibyajyoti Bordoloi is the creator and author of, a third-generation experienced fish keeper and owner of a successful pet breeding farm. He is also a member of the Center for Wildlife Rehabilitation And Conservation (Assam), the Marine Aquarium Societies of North East India, and the Kaziranga Nature Conservancy of Assam.