15 Best Tank Mates for a Black Ghost Knife Fish – FishLab

It is natural to want a tank mate that can bring some color and liven up your Black Ghost Knife Fish! Let’s take a look at the 15 Best Black Ghost Knife Fish Tank Mates!

The 15 Best Black Ghost Knife Tank Mates are fish that are just as large as the Black Ghost Knife and can survive in the same water temperatures. These can include Rainbowfish, gouramis, and even several species of catfish. 

In this article, we will cover not just a list of our top picks for companions to the Black Ghost Knife Fish, but also what makes those companions suitable. We’ll even give you a rundown of what to watch out for in any tank mates in the categories below. Let’s get started!

Black Ghost Knife Tank Mates – What You Need to Know

When caring for a Black Ghost Knife Fish, the best way to keep yourself and your tank happy is to master the categories of knowledge below, especially when choosing tank mates.

Temperament

The temperament of a Black Ghost Knife Fish is very peaceful. What you need is fish that can match that peacefulness instead of starting fights, being incredibly calm and relaxed. 

Size

The size of the fish that are with the Black Ghost Knife Fish should be about the same as the Black Ghost Knife itself. Though it is peaceful, as mentioned above, it can also eat or intimidate smaller fish. Make sure to get tank mates that are not significantly smaller than 18 inches (20cm) long.

Competition

 Food competition means that one fish who eats the same diet and in the same zone of the tank may bully another fish out of their share at mealtime. To avoid this, make sure fish are either able to fend for themselves at mealtime or have different diets. 

The Black Ghost Knife Fish eats a carnivorous diet of frozen and live foods like Brine Shrimp, feeder fish and earthworms.

Parameters ; Tank Setup

 The Black Ghost Knife Fish needs at least 100 gallons (400L), being a very large fish. It should also have a temperature of water in the range of 75 to 82 F (23C to 27C). If a fish finds this too warm or too cold, they won’t make a good tank mate for the Black Ghost Knife Fish!

15 Best Black Ghost Knife Fish Tank Mates

1. Silver Dollar Fish
2. Electric Blue Acara
3. Clown Loach
4. Cory Catfish
5. Bristlenose Pleco
6. Dinosaur Bichir
7. African Rope Fish
8. Saddled Bichir
9. Eartheater Cichlid
10. Angelfish
11. Sailfin Molly
12. Green Swordtail
13. Balloon Molly
14. Glass Catfish
15. Pictus Catfish

Let’s look more closely at each of these 15 fish above to see what makes them so great as tank mates to the Black Ghost Knife Fish!

1. Silver Dollar Fish

• Scientific Name: Metynnis argenteus
• Adult Size: 6 inches (15cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Medium Difficulty
• Origin: Guyana, Brazil

The silver dollar fish is sometimes considered difficult to take care of because it is so large. However, this fish is perfectly safe to be kept with your Black Ghost Knife Fish. 

The Silver Dollar Fish will add some shine to your aquarium. It has a round, silvery body, just like its name!

Pros of keeping with Black Ghost Knife Fish:

• No food competition
• No aggression

Cons of keeping with Black Ghost Knife Fish :

• None!

2. Electric Blue Acara

• Scientific Name: Adinoacara pulcher
• Adult Size: 7 inches (20cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: Venezuela

Another gentle giant is the Electric Blue Acara. It is peaceful and will avoid starting trouble with your Knife Fish. 

However, it is worth noting that the Electric Blue Acara will spice up the visuals of the aquarium with its reflective light blue body, fringed beautifully on the dorsal fin with lightning-yellow. It is technically a cichlid, but the Electtric Blue Acara is no bully unlike other cichlids. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• None!

3. Clown Loach

• Scientific Name: Cobitis macracanthus
• Adult Size: 8 inches (20cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Mild to Difficult
• Origin: Indonesia

The most difficult thing about keeping the Clown Loach is that it can become very large. With an already-big fish like the Black Ghost Knife in the tank, you’ll need a very big tank indeed to accommodate both!

If you can, however, you’ll have two tank mates who are similar enough in size to avoid hurting one another. In fact the Clown Loach is such a passive and peaceful species, you will often find them bunking together with your Black Ghost Knife in the same cave or other hiding spot. It is possibly one of the most compatible tank mates you will find.

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• Similar in Size

Cons of keeping with Black Ghost Knife Fish :

• Large Tank required

4. Cory Catfish

• Scientific Name: Corydoras aeneus
• Adult Size: 2 inches (5cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: South America

Another South American fish, the Cory Catfish is small but peaceful and will stay on the bottom of the tank. There is also strength in numbers; this bottom-feeder likes to school with more of it’s own kind. 

Cory Catfish like the Bronze Cory are iridescent, looking bronze in color but showing a whole rainbow of dull hues under the right light.

Pros of keeping with Black Ghost Knife Fish:

• Will clean up the bottom of the tank
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• None

5. Bristlenose Pleco

• Scientific Name: Ancistrus cirrhosus
• Adult Size: 5 inches (12cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: Amazon

This is another bottom-dwelling fish that can not only survive in the same conditions as the Black Ghost Knife, but is quite peaceful. 

Named for its bristly whiskers, this fish will clean up the bottom of the tank! At the same time, it will look interesting. 

Pros of keeping with Black Ghost Knife Fish:

• Will clean up the bottom of the tank
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• None

6. Dinosaur Bichir

• Scientific Name: Polypterus senegalus
• Adult Size: 18 inches (45cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Medium difficulty
• Origin: Africa

Another type of fish that is difficult mainly because it requires a very large tank, the Dinosaur Bichir works well as a tank mate for the Black Ghost Knife Fish. It is large enough to avoid getting eaten and mostly stays on the bottom of the tank.

As it lurks near the floor you’ll be able to see its long body structure. It even has a reptilian, snub-nosed, dinosaur-like face!

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• Different tank zone occupier

Cons of keeping with Black Ghost Knife Fish :

• None!

7. African Rope Fish

• Scientific Name: Erpetoichthys Calabaricus
• Adult Size: 24 inches (60cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: Nigeria

This fish is famous for its cute face, despite its long, snake-like body. Rope fish are ancient, and are sometimes also called reedfish. 

True to its adorable facial expression, the African Rope Fish is pretty laid back and won’t bother your Black Knife Fish. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• Large fish

8. Saddled Bichir

• Scientific Name: Polypterus endlicheri endlicheri
• Adult Size: 30 inches (76cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Difficult
• Origin: Nigeria

The saddled bichir has a sort of menacing look to its long body, flat head, and opaque eyes. However, it won’t bother your Black Ghost Knife Fish. 

An issue will only arise if there is not enough room in the tank. Saddled Bichirs need plenty of space, being one of the larger fish species. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression

Cons of keeping with Black Ghost Knife Fish :

• Large fish

9. Eartheater Cichlid

• Scientific Name: Geophagus
• Adult Size:  12 inches (30cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Medium difficulty
• Origin: South America

This is another member of the cichlid family that is somewhat unpredictable in terms of temperament. Some smaller varieties are relatively peaceful, while larger ones live up to the cichlid name by terrorizing the rest of the tank. 

However, since this fish is usually around the same size as a Black Ghost Knife Fish, even if you do wind up with a grumpy fish, it may not do much harm. These fish are colorful without the protruding forehead of a usual cichlid. 

Pros of keeping with Black Ghost Knife Fish:

• May not be aggressive
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• May be aggressive
• Large Fish

10. Angelfish

• Scientific Name: Pterophyllum
• Adult Size: 4 inches (10cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: South America

This tropical fish is beautiful. It will certainly add the color that your Black Ghost Knife Fish lacks, and is famous for its bright range of rainbow hues.

This fish can be semi-aggressive to smaller species, but because it is smaller than the Black Ghost Knife Fish, it won’t cause trouble. 

Pros of keeping with Black Ghost Knife Fish:

• No food competition

Cons of keeping with Black Ghost Knife Fish :

• May have aggressive habits

11. Sailfin Molly

• Scientific Name: Poecilia latipinna
• Adult Size: 3 inches (7cm)
• Compatible With: Black Ghost Knife Fish
• Care Level: Easy
• Origin: Louisiana

This fish is fun to watch just for looks alone! It is covered in pretty brown specks over its blue to silver body. It has a long, sail-like dorsal fin and protruding lips. 

This fish will not only survive in the same parameters as a Black Ghost Knife Fish, but it is fast and capable enough to avoid causing trouble with the bigger fish. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• None

12. Green Swordtail

• Scientific Name: Xiphophorus helleri
• Adult Size: 4 inches (10cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: Central America

The swordtail is named for its hilt-like tail fins. It is brightly colored, coming in all sorts of hues, with especially long and beautiful fins. 

Though this fish is smaller than the Black Ghost Knife, it is quick and peaceful. As long as there is room and shelter, it will not be preyed upon. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• None

13. Balloon Molly

• Scientific Name: Poecilia latipinna
• Adult Size: 3 inches (7cm)
• Compatible With: Black Ghost Knife Fish
• Care Level: Easy
• Origin: Central America

The Balloon Molly treats us to a unique appearance thanks to a spine deformity that slops it’s back, making it look like it has a potbelly!

This fish comes in many warm colors and is largely peaceful. It eats an omnivorous diet, but because of its smaller size it will not hog the Knife Fish’s food. 

Pros of keeping with Black Ghost Knife Fish:

• No food competition
• No aggression

Cons of keeping with Black Ghost Knife Fish :

• None

14. Glass Catfish

• Scientific Name: Kryptopterus bicirrhis 
• Adult Size: 5 inches (12cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: Asia

The glass catfish is named for one interesting fact that will blow your mind: it looks transparent! You’ll find a pair of whiskers and what looks like a fish skeleton floating in your tank. 

It will do no harm to your black ghost knife fish, either. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• No food competition

Cons of keeping with Black Ghost Knife Fish :

• None

15. Pictus Catfish

• Scientific Name: Pimelodus Pictus
• Adult Size: 6 inches (15cm)
• Compatible With: Black Ghost Knife Fish 
• Care Level: Easy
• Origin: South America

Finally, many aquarium hobbyists love the ease with which they can care for the Pictus Catfish. It can survive in many different scenarios and cleans the tank up while doing it. Being a bottom-dweller, it poses no threat to the Black Ghost Knife Fish. 

These fish are bright silver with whiskers as long as their bodies, forked fins, and pleasant little black spots. 

Pros of keeping with Black Ghost Knife Fish:

• No aggression
• No food competition
• Will clean up the tank

Cons of keeping with Black Ghost Knife Fish :

• None

In Conclusion

The 15 Best Black Ghost Knife Fish Tank Mates are those that can not only survive in similar water conditions, but are not too small to be safe from getting eaten, nor too aggressive to disturb the peaceful fish.

Some examples of these include the Pictus Catfish and the Balloon Molly! With these fish, you’ll have no trouble with a large, peaceful aquarium community.

It should be noted however, that not all the above 15 are essentially compatible with each other. So do your research first on each of these individual species before making your decision and remember that a Black Ghost Knife has an expected life span of between 10 and 15 years in captivity.