Black Ghost Knife Fish: Uncovering The Secrets of These Species

The Apteronotus albifrons, more commonly known as the Black Ghost Knife Fish, is a freshwater species that has been steadily growing in popularity. Well-known for their unique appearance and distinct behaviors, it’s no surprise why so many aquarists are drawn to them. 

But before you decide to get one, you should familiarize yourself with what owning one entails. In this article, we’ll cover everything you need to know about Black Ghost Knife Fish care. From tank size requirements to recommended tank mates to food and diet, we’ll make sure you’re well-informed on the topic. 

Blck Sword Knife Fish
A photo-realistic image of Black Ghost Knife Fish swimming in its tank, surrounded by colorful pieces of decor and plants.

Black Ghost Knife Fish hail from numerous South American countries such as Paraguay, Argentina, Venezuela, and Brazil. They can usually be found in the Paraná and Paraguay Rivers. The name of these fish comes from two sources – first, their obvious resemblance to a blade, and secondly, the local belief that ghosts inhabit the bodies of these fish. 

General Species Summary 

What’s truly remarkable about this species is that they’re electric! Black Ghost Knife Fish can use electric receptors to find hard-to-reach food sources. This is incredibly useful since they’re typically nocturnal animals. 


Generally speaking, a Black Ghost Knife Fish’s lifespan ranges from 10-15 years. It all depends on the quality of their care – both before and after purchase – and genetics. As the owner, you control most of the variables, so you’re in an advantageous situation to provide the best quality of life for your fish. 


It’s safe to say that Black Ghost Knife Fish look like no other species. Their bodies are long, thin, slightly curved, and is widest at their head. The tail is skinny and features two spaced-out white bands. Furthermore, they don’t have a dorsal or caudal fin. Instead, their momentum is generated by their pectoral and anal fins. This gives them a flowing swimming style that’s quite eye-catching. 

The color scheme of this species is typical of its namesake. These fish are almost entirely black and have only two white bands on their tail. There are rare cases where you may see some lighter colors on the top ridge of their body. 


Many people expect Black Ghost Knife Fish to be much smaller than they actually are. When fully grown, these fish can reach 18-20 inches in length, which is why a minimum tank size of 100 gal is required. Don’t fall into the trap of thinking that the size of the tank will control their growth – they will grow to their full size regardless of the aquarium size. 

Black Ghost Knife Fish Care 

Given their size, unique body type, and disease sensitivity, this species is not suitable for beginners. Black Ghost Knife Fish care requires an experienced aquarist. Consider every aspect of owning these fish before making a decision. 

Tank Size 

As stated before, a minimum tank size of 100 gallons is necessary for keeping one Black Ghost Knife Fish. It’s important to remember that bigger is always better when it comes to a home for your fish. Not only do they need space to swim around, but it also reduces the chances of aggression due to overcrowding. 

Water Parameters 

Keeping up with the water parameters is essential for healthy, happy fish. The ideal temperature for Black Ghost Knife Fish is between 72-86°F and the pH level should be somewhere between 6.5-7.5. Make sure to test the water regularly and keep an eye out for any changes. 

Tank Mates 

Due to their electric abilities, Black Ghost Knife Fish can be tricky to introduce to an aquarium. Aggression is also a concern with this species, so you should think twice about adding other fish to the tank. 

If you choose to do so, select non-aggressive species that aren’t much larger than the Black Ghost Knife Fish. We recommend species like Tetras, Corydoras, Plecos, and Gouramis. 

Food & Diet 

Feeding your Black Ghost Knife Fish is quite simple. They’re naturally carnivorous and appreciate a variety of live, frozen, and freeze-dried foods. Offer them blood worms, brine shrimps, tubifex, and high-quality flakes/pellets. 

Since they’re nocturnal creatures, feed your fish around nighttime when they’re more active. Additionally, we suggest breaking up their meals into two or three servings throughout the day. 

In conclusion, Black Ghost Knife Fish are magnificent creatures that require a bit of extra care. They’re relatively easy to look after once you understand their needs. Choosing the right tank size, tank mates, and diet will ensure your fish thrive in its environment. Hopefully, after reading this article, you feel informed and ready to take on the challenge of owning Black Ghost Knife Fish.


Black Ghost Knife Fish usually spend their days hiding in the shadows of plants or other pieces of decor. This is because they’re nocturnal so they rest during the day and start to hunt for food after the sun sets. They tend to be a rather solitary species and can sometimes even become territorial when housed with other fish. 


Black Ghost Knifefish are typically very hardy creatures. However, they are prone to various diseases such as parasites, bacterial infections, and skin flukes. It’s important to keep an eye out for any signs of distress such as abnormal swimming patterns, loss of appetite, discoloration, etc. Regular water changes and a proper diet can help prevent illnesses.


Black Ghost Knife Fish enjoy a wide variety of decorations in the tank. You can add driftwood, rocks, caves, and plenty of plants to provide them with ample hiding places and lots of mental stimulation. Since they’re active at night, you may even want to think about adding a few lights to the tank. 


The oxygen levels in the tank should be kept relatively high to ensure that your fish have plenty of oxygen to breathe. We recommend adding a few air stones to increase the oxygen levels and make sure there’s always plenty of oxygen available.


Black Ghost Knife Fish prefer slightly acidic water conditions with a conductivity range of 100-200 micro Siemens. To maintain optimal conductivity levels, use a water filter and monitor the levels regularly. 


Having an effective filter in the tank is absolutely essential. The filter should be strong enough to cycle the water every hour and also keep the water clean and clear. Make sure to change the filter media regularly to keep the water in tip-top condition. 


When it comes to breeding Black Ghost Knife Fish in captivity, there isn’t much information available. These fish are extremely difficult to spawn and it’s still unclear what triggers spawning behavior in this species. 


Regular maintenance is key to keeping your tank clean, clear, and healthy. Remove any algae and debris that accumulate in the tank, check the ammonia and nitrite levels, and perform water changes as needed. 


It’s always important to properly acclimate new fish to the aquarium. When introducing your new Black Ghost Knife Fish to the tank, add a few tablespoons of tank water to the bag every 20 minutes until the water has been completely exchanged. 

Final Thoughts 

Owning a Black Ghost Knife Fish is a rewarding experience, but it requires dedication and lots of knowledge. Being aware of their needs based on this article should help you provide the best care for them. With the right tank setup and environment, these fish will live a happy and healthy life.