Deep Dive – Black Ghost Knifefish


The Black Ghost Knifefish (Apteronotus albifrons) was one of the first tropical fish I was intrigued by in my early days of fish keeping. Seeing videos online and ghost knives in stores swimming any which way was fascinating and I quickly decided to purchase one. Over 4 years later and my ghost knife (Ghosty) is still easily my favourite. From his weird timid but curious nature to being able to hand-feed him my ghost knife has definitely made a mark on me.

Official Species Overview

Size: Up to 50cm
Temperament: Semi-aggressive
Temperature: 23-27
pH: 6.5-7.5
Diet: Carnivorous
Hardness: Medium (less than 200ppm)
Lifespan: Up to 15 years

My Experience

Upon doing my own research prior to purchase I was a little worried about my ghost knife possible being aggressive towards other fish and possibly snacking on some of my smaller fish (Cardinal/Emporer Tetras) once he grew. To my relief, I’ve never had any issue with aggression or snacking on smaller fish. Despite easily being the largest fish in my tank, the only time my ghost knife is remotely aggressive is when my nosy angelfish try to compete with him for food, a quick nip in their direction and they back off. Ghosty is currently around 20-25cm in length & 4.5 years old.

Ghosty lives on a mixed diet of primarily frozen blood worms & brine shrimp mixed with sinking pellets and the occasional zucchini he decides to hijack from the plecos in the tank. He eats the bloodworms/brine shrimp from my hands, sometimes that requires my holding the food to the edge of his cave while at other times he will come right out and eat from my hands near the surface.

Behavior wise Ghosty spends most of the day in his cave, currently a large hollow driftwood log, although he’s had many other housings ranging from smaller ornamental caves to a PVC tube and even a ship ornament. During the day it’s rare to see him exploring the tank unless it’s feeding time however at night he will happily explore the rest of the tank and frolic around. Some behaviour I’ve witnessed includes spinning around in a stream of bubbles and practicing a lunging attack forward


Overall my ghost knifefish has been a fantastic addition to my community tank providing hours of enjoyment. Despite some reports online of aggressive behaviour I’ve had no issues and my ghost knife who despite being the largest fish in the tank still acts timid. I would strongly recommend keeping a ghost knifefish to any intermediate fish keeper who is looking for a fun addition to their tank.