Black Ghost Knife Fish (Apteronotus albifrons) is also called as BGK and its a nocturnal fish that means it likes to roam at night time. The ghost knifefishes are a family, Apteronotidae, of ray-finned fishes in the order Gymnotiformes. These nocturnal fish have small eyes. BGK uses a high frequency tone-type (wave-type) electric organ discharge (EOD) to communicate. Many Apteronotids are aggressive predators of small aquatic insect larvae and fishes, though there are also piscivorous and planktivorous species.
It will grow to a maximum length of 25 inches (60 centimeters, 2 foot). It does not have scales. They are nocturnal, but they are weakly electric fish and use an electric organ and receptors distributed over the length of their body in order to locate insect larvae. They should be provided with a shelter (e.g. plastic tube, wood with hole) in which to hide. They will eat smaller fish in the tank and are intolerant of conspecifics. Attach a moonlight in aquarium to monitor them at night time.
There are also brown ghost knife fish.
I brought a black ghost knife fish. Quick info: It comes out at night (when aquarium is dark) and hides all the day in a wood or whatever it can find to hide. If provided aquarium moonlight it comes out as well. Haven’t seen em’ eating anything yet. Its a mysterious shy fish. I will post more info as I observe it more.