Black Ghost Knifefish

The black ghost is a South American fish with no dorsal fin and a long body shaped like a knife blade. With the wavy fin running along its belly, it glides forward and backward with equal ease. Its velvet-black body, the thin white stripe running from its snout to its forehead and the two white rings on its tail base are its most distinctive features.

It produces a weak electric field with an organ in its tail and, by sensing changes in this field, finds its way and searches for prey in the dark. It is harmless to humans. It is sold at 10 cm in stores but reaches 40–45 cm as an adult and is a nocturnal predator.

It lives in the large rivers of South America, in flowing, root-filled stretches with sand bottoms. During the day it hides among roots and in hollows, and at night it hunts insect larvae and small creatures.

• Volume: at least 400 liters and 150 cm length for an adult.
• Hiding tube: always provide a hiding place; a glass or plastic tube its body fits into is best. A fish that cannot hide becomes stressed and stops eating.
• Light and substrate: dim light, floating plants; a fine sand substrate.
• Water: very clean and well-oxygenated; moderate flow. It is sensitive to ammonia and nitrite and should go into a mature aquarium.

Carnivorous. Frozen bloodworms, brine shrimp, mysis, worms and small shrimp. It is best fed after the lights go out. Over time it also accepts sinking tablets and granules.

Usually calm toward other species, but it hunts small fish and shrimp that fit in its mouth at night. It is very territorial toward its own kind and similar knifefish.

Good companions: calm, medium to large species too big for its mouth: angelfish, gourami species, large tetras, calm cichlids, large Corydoras and plecos.

Avoid: neons and similar small fish, shrimp, fin-nipping species, a second ghost knifefish.

In a home aquarium a single fish is kept. More than one can only be tried in very large aquariums offering each individual its own hiding place.

Breeding in a home aquarium is very rare. Some of the fish in the trade are bred on farms in Southeast Asia.

• White spot: it catches it often because of its finely scaled skin; for treatment, halving the medication dose and supporting it with temperature is recommended.
• Medication sensitivity: sensitive to copper and many medications.
• Loss of appetite: usually caused by a lack of hiding places or poor water.

There is no reliable external way to tell the sexes apart.