Black Ghost Knifefish: Care, Breeding & Electrolocation


Black ghost knifefish are very popular – and for good reason.

These sleek fish can be mesmerizing to watch, and you can even train them to eat out of your hand. They’re one of the few electric fish out there and watching them interact with their environment can be a neat experience.

However, they also need more care than some of your average fish.

That’s why we’ve compiled this complete care guide to help you help your black ghost knifefish have the best life possible. We’ll discuss everything from diets to tank setups and even breeding.

So, if you’re looking to raise your own black ghost knifefish, keep reading.

Common Name:Black ghost knifefish (Apteronotid eel; the Black Knife)
Scientific Name:Apteronotus albifrons
Temperament:Peaceful but semi-aggressive towards smaller fish
Size:20 inches
Lifespan:10-15 years
Care Level:Intermediate
Minimum Tank Size:100 gallons


The black ghost knifefish can thank Amazonian tribes in South America for its common name, the ghost knifefish. This is because, among these tribes, there is a belief that the spirits of the dead inhabit the fish’s body.

The black ghost knifefish is mostly nocturnal, meaning it’s more active at night. As a result, it’s evolved to use electrolocation to navigate dark waters.

We’ll talk more in-depth about electrolocation and how black ghost knifefish use it below in the section about appearance.

Since they don’t have scales, black ghost knifefish are sensitive to diseases and improper water conditions. As a result, it’s important to set up your tank in a highly specific way in order to keep your fish healthy.

With proper care and tank setup, you can expect to enjoy your black ghost knifefish’s companionship for many years – up to 15!


When it comes to appearance, the name black ghost knifefish is anything but a red herring.

The black ghost knifefish is almost entirely black. The only exception to this are two white rings on its tail and a white stripe on their nose that may extend over the length of their back.

They also lack caudal and dorsal fins. This sharp and sleek appearance is what has earned them the name knifefish.

They do, however, have an anal fin. This fin is particularly large, stretching along the body from the belly to the tail.

Black ghost knife fish searching food at the bottom

As a result of this aerodynamic anatomy, they have a smooth yet speedy swimming style making them great predators in the wild.

Their body is also flat and elongated like a knife blade, and when they’re full-grown, they can reach up to 20 inches long. As a result, you’ll want a larger aquarium for these fish.

One of the most interesting aspects of the black ghost knifefish, however, is the fact they have no scales – much like an eel. This makes them sensitive to water conditions and infections, but it comes in handy for electrogenesis and electrolocation.


You may have heard of echolocation before – the process of using sounds to identity objects’ locations. Electrolocation is like that, only with electricity instead of sound.

Black ghost knifefish has an electric organ on the tip of their tail. They also have receptors all over their body, which is why they don’t have scales.

The black ghost knifefish sends out electrical pulses using the organ on their tail. They can then receive the rebounded pulse – or even pulses from other black ghost knifefish – through the receptor cells on their skin.

This electrogenesis allows them to navigate through even the dark waters of night and communicate with other black ghost knifefish.

Studies have shown that females emit higher frequency electrical pulses than males, which may aid during mating season.

Electrogenesis can also help black ghost knifefish find prey in the wild.

Food & Diet

Black ghost knifefish are carnivorous fish. This means that they get all of the nutrients they need from a diet consisting only of meat.

In the wild, black ghost knifefish feed on a wide variety of other animals, especially insect larvae, smaller fish, and worms. In a tank, it’s best to feed them fresh or frozen food – try to stay away from pellets.

Food options for black ghost knifefish include:

  • Bloodworms
  • Brine shrimp
  • Blackworms
  • Tubifex worms
  • Krill
  • Prawns
  • Crickets

While they prefer fresh or frozen food, it is possible to feed them dry food. However, it can take a long time for you black ghost knifefish to get used to eating pellets or flakes, and they may not enjoy it.

Whatever you decide to feed your black ghost knifefish, it’s important to make sure they have a varied and balanced diet. This helps ensure that your fish has the right vitamins and minerals.

For black ghost knifefish, who are so susceptible to illness and disease, this is even more important as a balanced diet helps boost their immune system.

Since black ghost knifefish are nocturnal you’ll want to feed them in the late evening or at night. They should be fed daily, and you should monitor them to make sure they’re eating all of their food in just a few minutes.

When you first get your black ghost knifefish, feeding may be difficult as they tend to be quite shy. However, after building a strong bond, you may even be able to hand feed them in the future.

Hand feeding can be difficult to establish, but the results are rewarding and will allow for more interaction with your black ghost knifefish. Just make sure to learn more before hand feeding your fish in order to do it safely.

Behavior & Temperament

For behavior, black ghost knifefish are freshwater fish from South America. They’re nocturnal, so you’ll mostly catch them being active after the sun has set.

They hunt and communicate with their environment using electrogenesis – much like bats and echolocation. They enjoy interacting with their surroundings and can often be seen swimming around their tank exploring.

For the most part, black ghost knifefish are pretty docile. They’re even shy!

Black ghost knifefish in vertical position

They won’t often interact with other fish in the tank (keep reading for the exceptions to that) and for the first few days, you may not even see them.

However, as they become more comfortable with their surroundings and have adjusted to their tank, you’ll notice them exploring. They’ll swim near the bottom of the tank by the substrate or near any plants you have.

While they’re mostly peaceful, black ghost knifefish can and will become aggressive if kept with others of the same species. They may also eat smaller fish.

As a result, choosing the right tank and tank mates for your black ghost knifefish is one of the most important steps in establishing a safe and healthy aquarium.

Habitat & Tank Requirement

The reason that black ghost knifefish aren’t recommended for beginners is because of how easy it is for them to fall ill due to disease or chemicals. They need a very specific tank set up in order to live a safe and healthy life.

Before you even set up your tank, it’s important to know that you should never use copper-based medicines for your black ghost knifefish. It is toxic and will make them sick, if not worse.

Black ghost knifefish in plants

Now, onto setting up your tank.

Since black ghost knifefish can grow so large, up to 20 inches, they’ll need at least 100 gallons. This varies based on how many fish you have in your tank, however.

Black ghost knifefish are native to South America, where they’re most often found in the Amazon River basin. This ranges from Venezuela all the way to Peru.

The waters in the Amazon River are rich with different types of vegetation. There are also lots of hides that provide shelter for wild black ghost knifefish.

The areas in the Amazon River where black ghost knifefish live are murky with low lighting and moderate water currents.

As a result, these shy fish will prefer a tank that best resembles their native habitats. They’ll enjoy a lot of plants, like water sprite, in their tank as well as plenty of places to hide.

Smooth rocks are also a good choice!

Your black ghost knifefish will spend a large amount of their time by the substrate. Since they don’t have scales – only skin – you’ll want to make sure to invest in a fine substrate to avoid injury.

Good substrate choices include sand or a very fine gravel substrate.

Due to the variety of water conditions in the Amazon River, black ghost knifefish are pretty resilient when it comes to their water. Just make sure it’s not brackish as they’re freshwater fish.

The proper water parameters for black ghost knifefish are as follows:

Your tank’s temperature should stay between 73 and 82 degrees Fahrenheit. However, if your black ghost knifefish develops Ich – which they are prone to – temporarily raising the water temperature to 86 degrees may be beneficial in treatment.

They also need a pH ranging between 6.0 and 8.0. It’s important to buy quality tests to make sure that the pH is never too acidic (low) or alkaline (high).

The hardness should be 5 to 19 dGH.

You may want to invest in a UV sterilizer for your fish tank to help prevent diseases without the use of harmful chemicals.

When setting up your tank, make sure to use pre filers and cover any open inlet tubes. Otherwise, you’ll find that black ghost knifefish have a tendency of hiding where they’re not supposed to be.

Tank Mates

Though black ghost knifefish can be aggressive to their own species and smaller fish, they can actually be great community fish. Just make sure to have a big enough tank and do your research on the best tank mates.

You’ll also want to make sure they have plenty of hiding spots for them to go when they need privacy.

After all, they’re shy!

Black ghost knifefish hides in plants

All tank mates should be at least 6 inches. Otherwise, your black ghost knifefish may consider them a snack rather than a friend.

They’ll also need to be calm and peaceful. That’ll help prevent any fights from breaking out if your black ghost knifefish is threatened.

Some of the best options for tank mates for black ghost knifefish include:

  • Cichlids (make sure they’re peaceful, however, as some varieties of cichlids are aggressive)
  • Catfish
  • Angelfish
  • Discus
  • Bala shark
  • Corydoras

If your black ghost knifefish is in a juvenile tank and you plan on moving it as it gets older, you can pair it with smaller fish that are the same size as your fish currently is. This includes:

  • Tetras
  • Guppies
  • Barbs
  • Rasboras

Avoid shrimp and snails, as your black ghost knifefish will eat them. And, do not house black ghost knifefish together unless your tank is large enough to allow them to establish their own territory (at least 80 gallons per fish).


When it comes to fish keeping as a hobby, black ghost knifefish aren’t commonly bred in tanks. There are special fisheries in Indonesia, however, that have managed to breed them using a secretive method.

Still, breeding your black ghost knifefish isn’t impossible. To encourage breeding, just make sure your tank has all the right factors:

  • A male and female pair
  • A large tank exceeding 100 gallons
  • An abundance of vegetation and hides
  • Proper tank homeostasis

The eggs are small, about 0.08 inches, and yellow. You’ll find them in a cave or hide, and they’ll hatch in about three days.


Taking care of fish can be hard. However, with the black ghost knifefish, it can be even more difficult due to how prone they are to sickness in improper tank conditions and disease.

That’s why we created this guide to help you raise your black ghost knifefish in a way so that they stay healthy and you can enjoy their entire 15-year lifespan with them. This involves proper tank set-up, feeding, and housing to make sure they’re safe and happy.

With enough time and care, you may even be able to hand feed your black ghost knifefish!