Care Guide for Black Ghost Knifefish – 18-Inch Electrical Oddball Fish

We get a lot of requests for this care guide because knifefish are such unusual-looking curiosities with an undulating fin that allows them to swim both forward and backward. While there are many kinds of knifefish, the black ghost knife (BGK) is the most readily available in the pet trade and often attracts the attention of beginners. It is larger than your average betta fish and can live up to ten years. Let’s first discuss how to keep this unusual fish happy and healthy over the long term.

What is Black Ghost Knifefish?

Apteronotus albifrons is a South American nocturnal fish that has weak eyesight and instead uses electrical signals to navigate its surroundings. The common name “knifefish” comes from the fact that it has no dorsal or caudal fin, giving it a blade-like appearance. Instead, an extended anal fin runs along the bottom edge of its body and ripples back and forth like a wave, allowing the knifefish to maneuver bidirectionally between tight spaces.

Depending on the size, most black ghost knifefish can be kept captive-bred. They may fetch $15-20 per month. Sometimes, young fish are sold in overcrowded tanks. They may get into problems with other fish. So make sure to buy a healthy one with both the white spots and a tail. This fish can live up to a year, so make sure you ask the staff member to feed it first before you take your knifefish home.

Find a healthy knifefish that has a good weight, active behavior, and its entire tail.

How big does a black ghost knife get? They can get pretty large if you are feeding them enough, so don’t be surprised if your baby knifefish matures into a 14- to 18-inch (35-45 cm) beast.

How fast do black ghost knife fish grow? In our care, we have seen them shoot up to 8 inches (20 cm) in the first year, and then the growth rate slows down to about 2 inches (5 cm) a year.

Are black ghost knifefish tough? Some people think they are “sensitive” fish that can’t live long. However, we have not had that experience. We have found that they do well when we feed them properly, don’t pick on them, and maintain good water quality. This is just like any other fish. Fish can usually handle one stress factor but health problems are more likely if there are multiple stress factors.

Can a ghost knife fish shock you? No, it is considered to be a weakly electric fish, in contrast to a strongly electric fish like the famous electric eel that can stun its prey. The electric organ of a knifefish generates a very weak electrical field, and then it has different sensing organs that can pick up the slightest distortions to this field, similar to a radar system. This detection system helps the knifefish to navigate its surroundings, locate prey, and communicate with potential mates or intruders.

How to Set Up an Aquarium for a Black Ghost Knife

Let’s discuss tank size. A 55-gallon aquarium might be okay for the first year, but it is too small for the long term. A 75-gallon fish aquarium is the next upgrade and may last for several more years. Ultimately, we recommend getting a 120- or 180-gallon aquarium for an adult black knife fish. They will do well with a pH of 6.8-7.8, temperature of 75-82degF (24 to 28degC), and GH at 5deg (90ppm). Create a heavily decorated setup with low lighting and lots of nooks and crannies – such as clear PVC pipes, rock caves, pleco caves, large driftwood, and aquarium plants. You can increase the size and comfort of your shelters for them as they get larger.

Plecos could argue with your knifefish over the best hides. So, provide more caves if you need.

Is the black ghost knifefish aggressive? In the right conditions, they can live in a community aquarium with other similar-sized, peaceful fish. You don’t want any tank mates bullying or outcompeting them for food, such as aggressive cichlids or fast rainbowfish. Your adult knifefish will happily eat neon Tetras and any small fish it can fit into its mouth.

What kind of fish can live with a ghost knife? Some hobbyists keep adult BGKs alongside peaceful catfish, geophagus cichlids and other friendly tank mates.

Two black ghost knifefish can live together? This is a common problem. Knifefish are territorial and don’t like sharing their space with other electric fish, such as baby whale fish, elephant nose fish, and other knifefish. Obviously, anything is doable if you have a large enough aquarium, but most people tend to keep ghost knifefish in undersized tanks.

What do Black Ghost Knife Fish Eat?

They are easy to care for and can eat a predominantly carnivorous diet. They will happily eat both sinking and floating fish, despite being bottom dwellers. Our worms are fond of brine shrimps, bloodworms as well as a wide variety of other foods, including worms, bloodworms or pellets. They will predate on small invertebrates and fish once they reach adulthood, as we have already mentioned.

Black ghost knives are shy at first. They want to hide in their favorite place until it’s time for them to eat. Many people have trained their black ghost knives to eat off their hands, or from the water surface with floating foods.

Black ghost knife can be used to teach Black to swim up to the surface to eat from your hand.

Can black ghost knife fish eat flaked food? Flaked food is not nutritionally dense enough to sustain them long-term, particularly since they are easily outcompeted by other fish for food. To help maintain their healthy weight, we prefer pellet, freeze-dried and frozen foods.

This is a great species to have as a showpiece fish. If you have done a lot of research and are willing to get a monster tank for its home, the black ghost knifefish may be the right pet for you. We do not ship fish. However, you can check out our recommended online retailers to see what stock they have.