Black ghost knifefish Care Guide: Diet, Tank Mates, Diseases, Breeding & More

Updated: November 30, 2022

The Black Ghost Knifefish is a beautiful, yet strange freshwater fish that is perfect for experienced fishkeepers.

These fish are not for everyone though, as they can be difficult to care for and are not recommended for beginners.

But if you’re up for the challenge, then a Black Ghost Knifefish might be the perfect addition to your aquarium!

Below, you’ll find everything you need to know about Black Ghost Knifefish care. Tank size, diet, lifespan, and more.

Species overview

The black ghost knifefish (scientific name: Apteronotus albifrons) is a freshwater fish that’s native to various parts of South America.

They are most commonly found in the Amazon basin but have also been spotted in other river systems in Peru, Brazil, and Columbia.

Black ghost knifefish prefer slow-moving waters with a lot of vegetation. This provides them with plenty of places to hide and forage for food.

These fish are nocturnal and are known for being quite shy. They are also very sensitive to changes in their environment and can be easily stressed.

Despite their shy nature, black ghost knifefish are still a popular choice for freshwater aquariums. They are especially popular with aquarium hobbyists who are looking for a fish that’s a little bit different.


Black ghost knifefish

The Black Ghost Knife is an eel-like freshwater fish that is easily recognizable due to its long, thin body and unique coloration.

As the name suggests, these fish are mostly black with a few white markings. The most notable of these is the horizontal white stripe that extends from the base of their tail all the way to their gill cover.

This white stripe is actually reflective and can be used as a defense mechanism. When predators are approaching, the Black Ghost Knife will “flash” this stripe and hopefully startle them long enough to make a getaway.

The body of the Black Ghost Knife is extremely long and thin. They have a small dorsal fin that is located near the base of their tail.

They also have a small anal fin and a forked caudal fin. Both of these fins are black with a white margin.

The Black Ghost Knife is a nocturnal fish, so they are most active at night. During the day, they will often hide in caves or other dark places.


The average lifespan of black ghost knife fish is around 5 to 8 years.

As with most fish, there are a number of things that can impact their lifespan. Things like poor water quality, stress from bad tank mates, or a suboptimal diet can all shorten their lifespan.


The average black ghost knife fish size is between 12 and 14 inches long when they are fully grown. Some have been known to grow up to 18 inches, but this is quite rare. They are a slender fish, so they don’t need a lot of width in their tank, but they do need enough length to move around comfortably.


Tank Size

The recommended tank size for a Black Ghost Knifefish is at least 125 gallons. This fish is a little bit on the large side and needs a tank that can accommodate its size.

Another reason why you need a larger tank is because this fish is a bit of a messy eater and produces a lot of waste. The larger the tank, the easier it will be to keep the water quality high.

Water Parameters

The Black Ghost Knifefish is a freshwater fish that is found in the Amazon Basin of South America. They are a nocturnal fish that prefer to hide during the day and come out to feed at night.

The Black Ghost Knifefish is a very delicate fish and needs to be in water that has the following parameters:

  • Water Temperature: 72-82 degrees Fahrenheit
  • pH Levels: 6.5-7.5
  • Water Hardness: 2-12 dGH
  • Alkalinity Levels: 4-8 dKH

What To Put In Their Tank

The most important thing you need to put in a Black Ghost Knifefish tank is a good filter. These fish are notorious for being messy eaters and they produce a lot of waste. A strong filter will help keep the water quality high and prevent any ammonia or nitrite spikes.

As for the substrate, these fish don’t really care. They’re not known for digging so gravel or sand will work just fine. Just avoid anything too small that they could potentially eat by mistake.

When it comes to plants, Black Ghost Knifefish don’t really bother them. This species is more interested in hiding so you can go with live or artificial plants without any issues.

Just be sure to leave some open swimming space in the tank. These fish like to move around a lot and they’re not shy about using their entire bodies to do so.

A few rocks or pieces of driftwood can be added for decoration, but be sure not to go overboard. Black Ghost Knifefish are known to get spooked easily and too many hiding spots will make them even more skittish.

Common Diseases

The Black Ghost Knifefish is a fairly hardy fish, but that doesn’t mean they can’t get sick.

The most common disease that affects this species is Ich. This is a parasitic infection that will present itself as white spots on the body of your fish.

If left untreated, Ich can be fatal. However, it is fairly easy to treat if you catch it early.

Another disease that can affect the Black Ghost Knifefish is infection from cuts. This is most common in fish that are kept in tanks with rough substrates (or with other aggressive species that like to fight).

The best way to prevent these fish from getting sick is to maintain the quality of the water in their tank. A tank with clean and stable water conditions always leads to healthier fish who are more resistant to disease.

Behavior & Temperament

The Black ghost knifefish is a nocturnal creature, so you won’t see much of it during the day. It’ll spend most of its time hiding in caves or other dark places in the tank. When night falls, it’ll come out to feed.

This fish is a loner. It’s not a social creature and does not do well when kept with other fish. In fact, it’s best to keep only one Black ghost knifefish per tank. Otherwise, you may see them fighting each other.

The Black ghost knifefish is an apex predator, so it’s not afraid to go after smaller fish. It’s known to eat fish that are half its size! If you do decide to keep more than one in the same tank, make sure they are all around the same size.

While they have a reputation for being aggressive, Black ghost knifefish are actually quite shy. They are easily scared and will often hide when they feel threatened.

Tank Mates

The black ghost knifefish is a unique and interesting species. It’s also one of the few animals on this list that’s not technically a fish!

Despite not being a fish, they can still be kept in a freshwater aquarium. These animals are often found in the wild in slow-moving rivers and streams.

The black ghost knifefish is a nocturnal species that’s most active at night. During the day, they like to hide in dark areas of the tank.

Because of their timid nature, it’s best to keep them with other peaceful tank mates. Some good options include:

  • Corydoras Catfish
  • Tetras
  • Guppies
  • Platies
  • Mollies
  • Swordtails


Black ghost knifefish are notoriously difficult to breed in captivity. In fact, it wasn’t until recently that the first successful spawning occurred in an aquarium.

The main issue is that these fish are extremely sensitive to changes in their environment. Even the slightest change can stress them out and prevent them from breeding.

That’s why it’s so important to create a stable environment for them. The water temperature should be between 82 and 86 degrees Fahrenheit. The pH should be between 6.5 and 7.5. And the water hardness should be between 5 and 15 dGH.

It’s also important to have the right setup. Black ghost knifefish prefer to live in blackwater environments with plenty of hiding places. That’s why a heavily-planted tank with driftwood is ideal.

When everything is in place, you can start to look for a breeding pair. These fish are solitary creatures, so it can be difficult to find a male and female that get along. If you can’t find a pair, your best bet is to buy six or seven juveniles and let them pair off on their own.

The next step is to trigger spawning. The best way to do that is to mimic the wet season in their native habitat. To do that, you need to raise the water level in the tank by about 10 centimeters. Then, you need to lower the temperature by a few degrees.

You should start to see the fish spawning within a few days. The female will lay her eggs in a hidden area, and the male will fertilize them. After that, he’ll stay close by to protect them.

The eggs will hatch within a week. The fry will be extremely small, so you need to be very careful when feeding them. Live foods like microworms and baby brine shrimp are best.

As they grow, you can start to introduce them to flakes and pellets. Just be sure to crush them up first.

Black ghost knifefish are difficult to breed, but it’s definitely possible with the right setup and some patience.


The Black Ghost Knife is a truly unique and amazing fish that is sure to stand out in any aquarium.

They are not the easiest fish to care for, but they are definitely worth the effort.

If you are up for the challenge, we highly recommend this fish. Just be sure to do your research and be prepared for a bit of a learning curve.