Black Ghost Knifefish
Scientific Name: Apteronotus albifrons
Common name: Black Ghost Knifefish, Ghost Knifefish, BGK on some forums
Size: 20” (65cm) in the wild, 12 to 14” more common in aquariums
pH: 6 to 8
Temperature: 23 to 28 C (73 to 82 F)
Habitat: South America – Amazon basin in Peru, Parana River from Venezuela to Paraguay
It was seeing a Black Ghost Knife for the first time that created in me a passion for “oddballs” that hasn’t died. For me, this is the most graceful and elegant of all fish available in the hobby, and considered by many to be one of the more challenging Knife Fish available. As with most Knife Fish, the Black Ghost is just as comfortable swimming backwards as it is forwards, and with an anal fin that extends almost the entire underside of the fish, they are beautiful to watch. The native people in the South American regions this fish inhabits believe that the souls of the departed take up residence in these fish, which is the reason for its commons name, Black Ghost.
General Characteristics:
An elongate and elegant fish, the Black Ghost Knife seems to be one long curve across the top of its body with an anal fin extending from just behind the head to just before its tail. The body of the Black Ghost is covered in extremely fine scales that give it a velvety look, and is solid black. There is no dorsal fin and no caudal (tail) fin. The tail instead is an extension of the body past the anal fin, and has two bright, white stripes across it. A white blaze down the forehead and nose of the fish finish its dramatic colouration.
The eyes are unusual-looking when compared to most tropical fish, as the Black Ghost Knife has developed other methods of navigating its surroundings. Whilst many people say that the Black Ghost is virtually blind, I tend to disagree as both Black Ghosts that I have kept have shown quick reactions to any movement near their tank. Their main method of navigation is the use of weak electric charges they generate within their bodies. Much like a bat navigates by sonar, the Black Ghost Knife uses the return signals from these electric charges to identify obstacles and potential food sources in their surroundings.
The incredibly fine scales of the Black Ghost mean that it is more susceptible than cichlid species to external parasites, in particular that old aquarium scourge, Ich or White Spot. As with other “scale-less” fish such as Clown Loaches and many catfish, treatment is difficult, as the “scale-less” nature of these fish make them intolerant of many of the medications used to treat external parasites.
Aquarium Set-up
The Black Ghost Knife is not a small fish, and whilst it is mainly nocturnal, it does require a good amount of space. A minimum of 75 gallons is recommended and it is good to have the required tank on hand when you first purchase you Ghost. My first Knife grew from barely 2.5” to 10” within the first eyar I had him. These fish do well in planted aquariums, either with real or fake plants, as the plants will give the fish a sense of security. They also require at least one hidey hole in which to spend the daylight hours. PVC pipe is often used, although make sure that the inside is smooth. The Black Ghost will sleep on its side during the day, so you don’t want anything in the pipe that might scratch or damage its skin. Many people use clear plastic pipes or even well-washed Coke bottles as refuges for their Black Ghosts. This gives the fish the sense of security it needs whilst allowing the owner to still see the fish during the day. It seems to make no difference to the Black Ghost if its hidey hole is black, clear, white or neon pink.
Substrate should be either very fine gravel or sand to imitate the fast flowing rivers this fish calls its home. Filtration is very important and over-filtering is recommended for this fish as it is with many messy cichlids. Extra current from filter outflows will not bother a Black Ghost at all. They thrive on highly oxygenated water and are well designed for swimming in strong currents. For all their delicate looks, they are a strong fish.
Feeding
Black Ghosts are mainly carnivorous, preferring meaty foods such as shrimp, beef heart, bloodworms and earthworms. Food should be prepared to a size that the Knife can manage. I have seem Black Ghosts offered for sale as small as 2 to 2.5 inches and at that size it is difficult for them to manage anything much larger than bloodworm.
Most Black Ghosts will ignore prepared foods and pet shop foods such as flake and crumble, but sometimes an odd one will come along, like my current one. Mine will eat almost anything, up to and including the zucchini I put in the tank for the small Pleco that I am growing out with him. This is very unusual, however, and you should be prepared to supply meaty foods in abundance. They are aggressive eaters that like to snack on a regular basis.
Black Ghosts are also well known for being able to be trained to hand feed. I had fed my first Knife, who was barely 2.5” when I first got him and I began trying to hand feed him right from the beginning to make sure he was getting enough to eat. I kept it up through the 2 years we had him and he would always seek out my fingers and brush against me when I had my hand in his tank. They can be a little nippy, although their bite is not very painful.
Compatibility
Finding tank mates for a Black Ghost Knife can be a tricky prospect. They are not safe with small fish such as Neon Tetras, being given to the occasional between-meals snack. They are good ambush hunters and will depopulate a community tank in short order. This is how I acquired my second and current Black Ghost.
For all their predatory nature, they are actually quite peaceful fish and can stress very easily when housed with boisterous fish. I recently tried adding my 4” Jack Dempsey to the tank with my Black Ghost to give the Dempsey a little peace from my 13” Oscar. Within a day, the Dempsey had displaced my 12” Knife from his cave and was constantly following him around the tank harassing him. It is most common for people to keep a Black Ghost as a single fish with the addition of a few peaceful bottom dwellers, such as smaller Pleco’s, Clown Loaches and other catfish. Some have schools of larger Tetra’s, such as Buenos Aires Tetra’s, but even those can be targeted by a Black Ghost. Their mouths are larger than you think.
It is not recommended to keep more than one Black Ghost to a tank. They are not tolerant of their own kind and territorial battles will ensue. Possibly a tank of 150 gallons or larger might be able to house two, but the electrical impulses they generate travel quite a distance through water and they will always be aware of each other. It has also been reported that they can pick up on the electrical impulses of other Black Ghosts and other electric fish, which can lead to “crossed wires” in your fish, each trying to interpret each other’s signals and becoming disorientated and damaging themselves.
Breeding
Breeding has not been reported in a home aquarium, mainly because it is so difficult to keep two Black Ghosts in the same tank. Although these are one of the two most studied electrical fishes in the world, little is known even to the scientific community about their breeding behavior.
Personal Experience
I brought my first Black Ghost Knife nearly 7 years ago and promptly spent the next two years absolutely fascinated by this fish. His personality and owner-responsiveness was definitely on a par with my Oscars. I lost him after two years to a bacterial infection that I could not treat. I was devastated by losing him and swore that I would never have another. A few years later, during one of my visits to the local pet shop, I spotted a half-grown Black Ghost, around 6”, that someone had returned after discovering it was responsible for the sudden decline in numbers of their community fish. I tried to be strong, but it took less than two weeks for me to give in and bring him home with me. I’ve had Streak II for nearly three years now and I wouldn’t be without him. These are challenging fish, especially when young, but worth every second of effort.
