A Complete Care Guide For Black Ghost Knife Fish (BKG)

The Black Ghost Knife Fish is one of the most magnificent creatures to keep in the aquarium hobby. 

Moreover, the unique fins of the knife fish allow them to move forward as well as backward. Hence, this attracts most of the spectators in front of the aquarium.  

There are multiple types of knife fish. However, the Black Ghost Knife is the most popular one among the fish keepers.  

The ghost knife fish falls under the category of medium-sized fish. Hence, it is not as large as most of the monster fish. However, they can comfortably grow and live in a 100-150-gallon fish tank.  

However, you should always keep in mind that the knife fish lives for more than a decade. Hence, you should have a long-term commitment.  

This article seeks to provide a comprehensive guide to caring for the Black Ghost Knife Fish. 

What Is A Black Ghost Knife Fish?

The Black Ghost Knife Fish is a South American fish that is nocturnal in nature. The fish tends to have very weak eyesight during the day. Hence, the fish depends on the electrical frequency to move around the aquarium. 

1. How Does The Black Ghost Knife Fish Look? 

The fish lacks a dorsal or a caudal fin. The ghost knife fish has one single, elongated, wavy anal fin. 

The fish gets its majestic, knife-like appearance from the elongated anal fin, which mesmerizes the spectators when it moves back and forth. 

In addition, the fish has a white stripe on its forehead and tail. Often, hobbyists from diverse regions also refer to the fish as “feather fish”.  

The structure and posture of the fish also give it a feather-like appearance. The fish can swim bidirectionally. Hence, the black ghost knife often resembles a levitating feather in clear water. 

2. How To Choose The Right Black Ghost Knife Fish? 

Most of the black ghost knife fish are bred in captivity. Moreover, they come in very small sizes. The sellers often keep too many knife fish in a very small space. 

This often creates a problematic situation. The fish often nibble on each other’s fins and tails. Thus, you should have two stripes on the tail of the fish. 

Moreover, the two stripes on the tail of the fish indicate that their fins have been intact. Additionally, ask the seller to feed the fish. 

Too many fish in the same space often spikes the levels of ammonia and nitrate in the aquarium. 

This can prevent the fish from feeding properly. Thus, asking the pet store to feed the fish allows you to get an idea of whether the fish is healthy. 

Always ensure to bring a healthy ghost knife to your home. Remember, the fish has a lifespan similar to that of a dog.  

3. What Is The Size Of The Ghost Knife Fish?  

The fish falls into the category of medium-sized fish. Hence, they do not grow as large as monster fish like Arowana or other variants of knife fish, such as clown knife fish. 

However, they can get considerably large. A ghost knife fish can grow upto the size of 14-18 inches. Hence, you should bring it home while keeping future needs and requirements in mind.  

4. How Fast Can Does Feather Fish Grow? 

The growth of the fish kind of varies. Not all fish grow in the same way. Moreover, several factors, such as aquarium size and its surroundings, influence fish growth. 

However, when you provide the fish with adequate space and enough protein-rich, nutritious food, it often grows up to 8-10 inches within the span of only one year. 

5. Is The Feather Fish A Resilient Fish? 

People often believe in the myth that they are sensitive fish. Hence, they tend to have a shorter life span.  

However, that is not the case at all. Moreover, the fish lives for more than 10 years if you efficiently lower the nitrate and nitrite levels in the tank. 

Adding compatible tankmates that help ensure they are not bullied by other fish and that water quality is maintained helps ensure a long lifespan. 

The fish is sturdy and therefore handles stress efficiently. It is a nocturnal species. Thus, the black ghost knife fish, or the feather fish, enjoys hiding in spaces. 

6. Can I Get Electrocuted By A Ghost Knife Fish Or A Feather Fish? 

The Ghost Knife Fish produces less voltage or a smaller charge to navigate around. On the other hand, a strong electric fish like the Electric Eel produces a shock of 800+ Volts. 

A Ghost Knife Fish produces only 1 volt of charge. Moreover, this helps in navigation.  

In contrast, Electric Eel uses its charge to stun its prey. This electrical field, generated by the Ghost Knife, is used to detect the slightest distortions in it.  

The highly sensitive sense organs can detect the movements of other organisms while detecting distortions. This system compensates for the fish’s weak vision.  

What Is The Best Aquarium Setup For A Ghost Knife Fish?

Initially, you can start with a comparatively smaller aquarium. Moreover, a 55-gallon tank does great for the first year.  However, it restricts long-term growth.  

A 75-gallon tank can be helpful for the upcoming years. However, a fully grown adult Ghost Knife Fish can live for the rest of their life in a 150-180 gallon fish tank. 

The most suitable pH for the Fish is 6.8 to 7.8. You should maintain the aquarium temperature between 75 and 82°F.  

Furthermore, maintaining a 5° (90 ppm) GH provides the most suitable conditions for a long lifespan. 

A heavily decorated setup with dim lighting does really well. The aquarium should have ample hiding spaces. 

Adding a glass tunnel often makes them feel like they are hiding from you. However, you can easily see the majestic movement of the fish in the transparent glass tunnel. 

The fish loves to stay around natural aquarium plants. However, do not add it to a planted aquarium with a CO2 system. The fish does not do well at higher CO2 levels. 

1. Is A Black Ghost Knife Fish Aggressive? 

The Black Ghost Knife fish are generally calm. Moreover, they can easily live in community aquariums.  

You should avoid aggressive cichlids and other fast-moving fish. These fish are very similar to monster fish. Thus, they often eat any fish that fits in their mouth. 

Hence, you should avoid keeping fish like the neon tetras, guppies, or any other small fish that easily fit into the mouth of the Ghost Knife.  

2. Which Are The Best Tank-Mates?

Any peaceful fish that is larger than 6 inches can be easily accommodated with the Black Ghost Knife. 

Moreover, this includes peaceful fish such as geophages, cichlids, catfish, angelfish, and several other friendly fish. 

3. Can More Than One Ghost Knife Fish Live Together? 

The knife fish navigates through electric charge and electric signals. Thus, you should avoid keeping knife fish with other fish that depend on electrical frequencies to move around. 

Hence, this includes baby whale fish, elephant nose fish, and other knifefish. However, large aquariums can accommodate a wide range of fish. 

What Do Black Ghost Knife Fishes Eat?

Black Ghost Knife Fish eat different types of things. This includes different types of worms, such as bloodworms, pellets, and brine shrimp, as well as other frozen foods.   

The fish is a carnivore. Thus, you should provide worm-based protein to your Ghost Knife Fish.  

Large-sized knife fish also enjoy hunting down and eating large-sized fish like guppies. During the initial days, the Black Ghost Knife fish often acts shyly.  

Thus, they hid most of the time at their hiding spot. However, when they are hungry, they can eat from all levels of the water. 

Frequently Asked Questions (FAQs) 

Here are the answers to some of the most commonly asked questions about Black Ghost Knife Fish.