Black Ghost Knife

Black Ghost Knife
Black Ghost Knife
Black Ghost Knife
Black Ghost Knife
One of the most unique and attractive community fish available today is the magnificent Black Ghost Knife. These majestic fish hover using a wave like motion just above the aquarium substrate and have a unique ability to swim both forwards and backwards.

Common Name(s) : Black Ghost Knife, Knife Fish, Black Ghost

Family : Apteronotidae


Species : Apteronotus albifrons

Origin : South America

PH : 6.0 – 8.0

Hardness : Soft to Hard

Temperature : 23 – 28°C / 73–82°F

Maximum Size : 30cm / 12″ (in most aquariums) ; 50cm / 20″ in wild

Lifespan : 7 – 15 years

Aggression Level : Medium (6/10) Will eat small fish

Recommended Tank Size : 150 Litres +

Strata : Bottom


They prefer a dimly lit tank as their eyesight is optimized for low light. Plenty of caves or a heavily planted tank is ideal for Ghost Knives. Commonly enthusiasts will use a short piece 75-90mm PVC Pipe to provide the necessary shelter for them.


  • Large / Medium Tropical Fish
  • Most Cichlids
  • Dwarf Cichlids


Carnivores – feed them bloodworm or brine shrimp. I find if a good quality flake food is used then often Black ghost Knives will accept it (but not always!)


Breeding in an aquarium has been reported, these were two very large specimens, however generally breeding is unheard of. Black Ghost Knives are bred readily in Asia on farms – but to achieve these results the animals are commonly injected with hormones to induce spawning.
They remain extremely difficult to sex, some sketchy suggestions to determining the sex include..

– A male may a head shaped a bit like a horse
– A male may feature a thicker line down its back, the female obviously a thinner line
– A female may be thicker through the body
– Someone even suggested they might change sex !!

So your guess is as good as mine but if you take any value out of any of the above suggestions, or can add to them, I’d love to hear from you !!


Black Ghost Knives originate in South America, where they inhabit the Amazon River basin. Black Ghost Knives can be found in fast moving rivers and streams with sandy bottoms. In the wild, Black Ghost Knives are nocturnal and feed on insect larvae during the night.
In the aquarium, due to its sensitivity to light, generally a Black Ghost Knife will seek refuge in some rocks, driftwood, amongst plants or even a piece of PVC pipe if provided. They are carnivores and will readily accept frozen bloodworms or brine shrimp. You can certainly train your ghost knife to eat a block of frozen food from hand – I particularly think this is a great idea to get a young Ghost Knife eating if it refuses to eat.
Black Ghost Knives grow to a large size – up to 60cm has been recorded – but more commonly will grow around 30-40cm. For this reason it is strongly suggested an aquarium of around 300 litres be considered.
Surprisingly, even a large sized Black Ghost Knife feature a peaceful temperament. However it is recommended that larger specimens are not kept with fish small enough to fit in their mouths as when the lights are off as this fish becomes predatory in the dark. In a smaller tank, it is not recommended that Black Ghost Knives be kept in the same tank as they will show aggressiveness to one another.
Ghost Knives are a scale-less fish that will be very sensitive to medications. Care should be taken – and it is strongly suggested that no more than half the recommended dose be allowed when medicating is necessary – particularly with copper-based medications.
Black Ghost Knives emit an electrical current that they use to navigate and hunt for food. Don’t panic – it is not anything that will ever affect you and the charge would never be noticed.
An Albino variety – aptly named the “White Ghost Knife” is also sometimes available.


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