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Black Ghost Knifefish Care, Feeding And Breeding

I clearly remember the first time I saw a black ghost knifefish. Their unique beauty amazed me. So, naturally, I wanted one for my collection. Before adding one to my aquarium I did extensive research to understand the fish and their behavior. With that information, I prepared this guide for you. If you are here that means you are amazed by this fish as me. Let’s find out how to take care of this black beauty.

The Black Ghost is pitch black in color, with a hint of dark blue, and the ghost-like fin that runs along the lower part of the fish is iconic. Black Ghost has a white ring on its tail and a white mark on the head, which may run back to its tail. An average Black Ghost Knifefish grows a little over 30cm(1ft). The name originates from the South African natives’ belief that the dead are reincarnated in the form of a Black Ghost Knifefish. 

Black Ghost Knifefish

Quick Overview

Common nameSquare starfish
Square biscuit starfish
Care levelModerate 
Reef CompatibleReef safe 
Native toSouth Australia, Western Australia, Sydney, Victoria, and Tasmania
Color Bright orange color 
Tank size50- 100 gallons tank 
Preferred temperature72 to 82 Fahrenheit
Other water parameters pH level- 8.1-8.4
Hardness level – 8-12 dKH 
Preferred salinity1.023 to 1.025
SizeGrow up to about 35 cm 
Temperament Peaceful 
Recommended tank matesNon-aggressive corals and saltwater fish 
Preferred foodSponges
Sea squirts,
Bryozoans, and
Feeding frequency2 or 3 times per day 
Propagation bySexually and asexually 

Habitat of Black Ghost Knifefish

Knifefish favors the tropical climate. Freshwater lakes with sandy bottoms are ideal for them. Dark places to hide inside are places most likely that Black Ghost inhabits. 

Black Ghost as a nocturnal hunter

The Black Ghost Knifefish is nocturnal and carnivorous in nature. Although they are friendly in the presence of larger fish. But they get aggressive among smaller or same-sized species. They feed on worms, small insects, and other smaller fish. An interesting fact is that these fish can hunt using electric waves generated by them to guide them in the dark.

Black Ghost Knife Fish Varieties

The Electric Black Ghost

The Black Ghost belongs to the Weak electric fish category. It is curious how they can produce not only electric impulses but also sense impulses, unlike most other types of electric fish. They use these impulses to guide themselves at night when they hunt down prey. Apart from that, they use electric signals to communicate with others of their own kind. They maintain almost the same frequency for themselves, and female Black Ghost Knifefish tend to have higher frequencies than males. 

Petting Black Ghost Knife Fish

Black Ghost Knife fish has semi-aggressive behavior when trained well; the Black Ghost is known to be trusting and loyal as if it’s a puppy living in the water. After providing an environment with proper conditions, a Black Ghost can be trained with regular activities. Feeding around the same hours of the day and making them come to the surface are examples of such activities. After some time, they gradually start to trust the owner and may rest on the hand or feed from the hand as any other pet would. 

Black Ghost Knifefish is a unique type of fish. It has nocturnal, weak electric nature. Also, it has a very loyal behavior as a pet. Because they are unique, many pet lovers pet them as their favorite pets. Even some fish hobbyists pet them themselves as well. 

How does Big Do Black Ghost KnifeFish get?

Typically, Black ghost knife fish grow up to around 19 inches or 50 cm. but in some cases, this type of fish reaches about 23 inches or 60cm long.  Additionally, some research findings revealed that the Black ghost knife fish’s average size ranges from 5 to 6 inches or 12 to 15 cm. Further, the important thing is, that these fish grow faster, and if you feed and care for them properly, they will reach their maximum size immediately.  Therefore, Black ghost knife fish definitely stole the large space of your aquarium.

Is Black Ghost KnifeFish Aggressive?

Usually, this fish belongs to the peaceful fish category. But they may show quite aggressive behavior towards other knife fish. However, when they are stressed or feel uncomfortable with their environment, they can show aggressive behaviors. 

Black Ghost Knifefish Behavior

Generally, Black ghost knife fish is shy because they are not much social. Also, the Black ghost knife fish is a peaceful fish type. However, if you keep them with their own company, they will surely live homogeneously. But most probably, they show aggressive behaviors when they keep with other knife fish. 

On the other hand, when they are stressed and feel the danger, they will probably be aggressive to similar-sized or small-sized fish in your aquarium. In addition to that, another crucial behavioral characteristic is these fish are nocturnal. It means that the Black ghost knife fish is very active in the nighttime than in day time. Most probably, they spend their daytime in hidden places in the tank. But they do not totally disappear in the daytime.  

Once they feel comfortable with the environment, you can find out them at the bottom of the aquarium. But if you notice that they only come out from the hidden places at night, they are not comfortable in the environment. However, they do not swim near the surface, even at night time. You can find them close to the substrate and foliage. Also, their eyesight is not well developed, but they use their electronic field for hunting and communicating. 

How long does Black Ghost Knifefish live?

As usual, Black ghost knife fish can live around 10 years. But you have to look after them well. Because care level directly affects the lifespan of any fish. In addition to that, sometimes their lifespan can be extended up to around 15 years. 

Black Ghost Knifefish

Black Ghost Knife Fish Care

generally, the Black ghost knife fish is one of the easiest care for aquarium fish. When it comes to the care of this fish, the most important thing is that you should highly consider their scaleless sensitive skin. But do not worry. If you maintain better tank condition, it will not be a challenge for you. So, Let’s see in deep. 

Black Ghost Knife Fish Tank Size

This fish is quite large. So, you should need a pretty large aquarium to live them happy. Therefore, you should need at least 100 gallons for your Black ghost knife fish. But if you wish to go with a few Black ghost knife fish, take a tank with at least 150 gallons capacity. However, if you want to set up a community tank, the tank size depends also on the other fish species and their requirement. But you have to go for a tank that is more than twice or thrice the size mentioned above. 

How Many Should Black Ghost Knife Fish Be Keep Together?

I recommended keeping two Black ghost knife fish in the same tank. But you should make sure they have enough space in the tank. If you want to keep more than two, there is a risk and potential of aggression. Keep it in mind. 

Tank Setup   

It is better to pay attention to hiding places in your tank. Because if you set up adequate hiding spots, they will definitely appreciate you because Black ghost knife fish are pretty shy. Further, you can use smooth rocks and plants to build up these places. But when you set up the tank, you should remember that this fish is scaleless and has sensitive skin. So, you should select all items that are not able to injure them. 

Also, it is better to choose a fine substrate for their tank. Because sharp gravel can be injured them, it is very best to use sand at the bottom of your tank. But if you want to lay gravel, you can select a very fine gravel mix. You can decorate the tank with live plants. The advantage is Black ghost knife fish do not eat and damage the live plants.  Therefore, you can go with many plant species. But Black ghost knife fish deal well with high foliage plants like water wisteria.  

Also, wood and logs are a perfect addition to your tank because they create excellent fish hiding spots. But it is better to keep them on the sides, and it allows to create of enough space for fish to swim freely. Generally, this fish species love to live in dark conditions. So, you can use medium brightness subdued lightning. But here, you should consider the lighting requirement of other fish species too. 

The other most important thing is the filtration system, and you should select a better filter with enough capacity. On the other hand, some hobbyists noted that the Black ghost knife fish try to hide in the canister filter or tubing. So, to avoid this, you can use pre-filters or cover any open inlet tubes. Further, installing a UV sterilizer help to protect this scale-less fish from infections. 

Water Quality Condition

It is crucial to keep ideal water parameters in your Black ghost knife fish tank. Let’s see the perfect amount of each water parameter. 

  • You should keep the water temperature between 73-82 Fahrenheit
  • The ideal pH level ranges from 6.0 to 8.0 
  • It is better to maintain the hardness level of the tank water between 5-19 dGH.  
  • You should test the water once per week to ensure that nitrate and ammonia level is below 20 ppm. but if you can keep them at the lowest amount, it is better 
  • Black ghost knife fish live happy with medium to strong water flow
  • Further, keep in mind that Black ghost knife fish is freshwater fish and does not tolerate any brackish conditions

Special notes: You have to perfume a 30 to 50% water change per week because it helps to create better water conditions for your Black ghost knifefish. 

Black Ghost Knife Fish Breeding 

Black Ghost Knife Fish Male Or Female Identification

There are no significant or visible features to distinguish between female and male Black ghost knife fish. But we have only one option, and it is electric fields that they generate and emit.  According to the research findings, the female fish create and emit more electric signals at a high frequency than the male fish. As a result of this, female fish more responds to companions and foods than male Black ghost knifefish. 

Black Ghost Knife Fish Breeding

Breeding black ghost knife fish in captivity is complicated, and little is known about the technique because you cannot do this in your home aquarium. Indonesian fish keepers are famous for breeding this fish species. Generally, adult black ghost knife fish is nearly 10-15 inches. So, if you breed them, you should have an extremely large aquarium. 

Because of these, Indonesian fish breeders use large ponds for breeding black ghost knife fish. How to breed your Black ghost knife fish? Firstly you should have the below things to succeed in the breeding process. 

  • A suitable and matured pair of Black ghost knife fish to mate 
  • An extremely large aquarium is situated in darkened location. This place must be silent and away from excessive movements.
  •  Large marbles, pebbles, and plants will protect the eggs from the parents. Because after laying eggs, parents tend to eat them. 
  • You should maintain the water temperature at 27 oC. 
  • It is important to perform a consistent water change. It is recommended to perform a 25-50% water change every two days. This motivates the breeding process. 

You can set the tank and allow the pair of fish to live freely. Here you should maintain the ideal water parameters. Also, free of stress and a non-threatening environment empower successful breeding. Also, you should set a safe environment unless female fish does not lay eggs. After laying eggs, you should separate your parents. The eggs are yellow in color and 0.08 inches in size. Also, eggs take around 3 days to hatch. 

How many babies do Black Ghost Knife fish have?

Generally, female Black ghost knife fish lay around 500 eggs at one time. 

Black Ghost Knife Fish Fry Care

After the fry come out from the eggs, you should feed them using small foods. The most suitable foods for frying are baby brine shrimps, infusoria, and broken flake foods. Also, you should care about the water conditions and safety of these little babies. 

Feeding Behavior Of Black Ghost Knife Fish 

Feeding your fish is the most vital thing in Black ghost knife fish care. Because it directly affects the life of your fish. So, if you want to keep your fish happy, you should highly care about its feeds. 

What Do They Eat (In The Wild And In Aquarium)?

Black ghost knife fish is carnivores. So, they eat only animal matter. 

In the wild  

Several foods in the wild can be found by Black ghost knife fish easily. Mostly, insects, juveniles, fish, and small crustaceans are mainly included in their diet in the wild. 

In aquarium 

There are many options to make a happy diet for your Black ghost knife fish in captivity. You can go with the below list. 

  • Daphnia 
  • Brine shrimps 
  • Meaty frozen foods 
  • Bloodworms 
  • Black worms 
  • Tubifex Worms
  • Krill prawns 
  • Crickets 
  • Mosquito larvae
  •  Feeder fish 
  • Small pellets and flakes 
  • Peas 
  • Frozen community fish foods 

Special note

  • Please do not feed them dry foods. 
  • Also, it is vital to provide a balanced diet for your fish anytime. 

How Often Should You Feed?

It is better to feed your Black ghost knife fish daily. Also, you should feed them several times per day. When considering the correct amount of food, you can provide feeds that fish can finish within a few minutes. However, it is crucial to avoid overfeeding. 

When Should You Feed Your Black Ghost Knife Fish (Time Of The Day)?

You can feed them both in the daytime and nighttime. But Black ghost knife fish is more active in the nighttime. So, when night, you can notice that they are fed actively. However, if your aquarium is lightning with subdued, it is more effective to feed your Black ghost knife fish at night time. 

How Can Long Black Ghost Knife Fish Go Without Food?

The period will depend on the availability of food in your tank. But do not strike without providing food to your Black ghost knife fish because it directly impacts their health. So, as a fish owner, you have to be a responsible person. 

Black Ghost Knife fish tank mates?

Generally, the Black ghost knife fish is a kind of peaceful fish but not like other knife fish. Also, they are shy. When you choose tank mates for your Black ghost knife fish, you should remember the above factors. As well, you should consider the tank conditions and other requirements of both fish species. If not, you have to face unfortunate surprises. So, I will ease your task, and you can go with the below list. 

  • Large peaceful cichlid species 
  • Catfish 
  • Angelfish
  • Discuss 
  • Corydoras 
  • Mono Sebae 

However, do not choose tiny fish and other creatures as tankmates of Black ghost knife. Because knife fish will consider them as prey. Also, do not select aggressive fish species. 

Related questions 

Is Black Ghost Knife Fish Aggressive?

Black ghost knife fish is peaceful fish species. But they are aggressive when dealing with other knife fish in the same tank. Also, lack of space and hiding spots also motivate them to be aggressive. But this fish is a good addition to community tanks. 

How Do Big Dragon Gobies Get?

Normally Black ghost knife fish has the ability to reach a maximum length of 10 to 15 inches. 

Can Black Ghost Knife Fish Live In A Pond?

Yes, Black ghost knife fish can live in ponds. For instance, when breeding this fish, hobbyists need large tanks. But it is difficult to find out. So, Indonesian Black ghost knife fish breeders use ponds for breeding them 

Credit to: More Aquarium Co-Op
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About Dr.Chamika

Hello, I'm Dr. Chamika. I am a Researcher in Water quality, Aquatic organisms, and Environmental chemistry. I am a passionate fish keeper, with10 years of experience. My mission is to help other aquarists experience the joy of fish keeping.