Black Ghost Knife

Black Ghost Knifefish – A Unique and Mesmerizing Aquarium Fish

The Black Ghost Knifefish (Apteronotus albifrons) is one of the most fascinating species in the freshwater aquarium hobby. Native to South American waterways, this fish is named for its knife-shaped body, deep black colour, and the spiritual significance it holds in some Amazonian folklore.

What makes this species truly unique is its undulating swimming motion, powered by its long anal fin. This allows it to glide smoothly through the water and even swim backward just as easily as forward. The Black Ghost Knifefish is nocturnal and uses weak electrical pulses to navigate and detect prey—an incredible adaptation that sets it apart from most other fish.

Tank Setup & Care

To thrive, Black Ghost Knifefish need a spacious aquarium with plenty of hiding spots, such as driftwood, rock formations, PVC or glass tubing, and dense planting. A soft sandy substrate and floating plants help create a natural environment. While generally peaceful, they do not tolerate their own species or other fish that generate electrical signals. They can reach up to 50 cm (20 inches) in length, so a minimum 450L (120-gallon) tank is required for an adult. Strong filtration and regular maintenance are essential to maintain water quality.

Feeding

In the wild, these fish prey on small fish and invertebrates. While they have relatively small mouths for their size, they should not be housed with tiny tankmates that could be seen as food. Our tank-raised juveniles are currently eating a variety of frozen and live meaty foods, and some are also accepting high-quality dry foods.

Why Choose the Black Ghost Knifefish?

✔️ Incredibly unique swimming style
✔️ Striking appearance
✔️ Relatively peaceful with non-prey species
✔️ Easy to care for in a well-maintained tank
✔️ Won’t damage plants

Recommended Tank Parameters

• Temperature: 23° - 28°C

• pH: 6.0 - 7.5

• KH: 5 - 10 dKH

• Minimum Tank Size: 450L+ (120+ gallons)

Care Guidelines

• Diet: Carnivore – requires a varied diet of frozen, live, and high-quality meaty foods

• Temperament: Peaceful with larger fish but intolerant of its own species

• Origin: Tank-raised, native to the Amazon Basin

• Max Size: Up to 50 cm (20 inches)

• Average Purchase Size: 5 - 7.6 cm (2 - 3 inches)