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. There are many types of knifefish available, but the black ghost knife (BGK), is the most common and sought-after. It is larger than your average betta fish and can live up to ten years. Before you make the commitment, let’s talk about what it takes to keep this intermediate-level oddball fish happy and healthy in the long term.

What are Black Ghost Knifefish?

Apteronotus albifrons, a South American nocturnal sea fish with weak eyesight, uses electrical signals instead to navigate its surroundings. It lacks a dorsal nor caudal fin which gives it its common name, the “knifefish”. An extended anal fin runs along its bottom edge and ripples backwards like a wave. This allows the knifefish to maneuver in bidirectional fashion 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. You can expect this fish to live for as long as a pet dog. Ask the employee at the store to feed your knifefish before you bring it home.

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

How big can a black-ghost knife get? If they get enough food, they can grow quite large. Don’t be surprised to see your baby knifefish grow into a massive 14- to 18-inch (35 to 45 cm) fish.

How fast does black ghost knife fish grow in their care? After the first year, they reach a height of 8 inches (20cm) and then slow down to 2 inches (5cm) per 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. Usually, fish can handle one stress factor, but multiple stress factors will increase the likelihood of health issues.

Will a ghost knifefish shock you? This is because it is weakly electric, unlike a stronger electric fish like an electric eel. An electric organ in a knifefish creates a weak electrical field. Then it has various sensing organs that can detect any distortions to this field. This is similar to a radar. This detection system allows the knifefish navigate its environment, find prey, and communicates with potential mates or other 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 can tolerate a pH between 6.8-7.8, temperature between 75 and 28degC (24-28degC), as well as GH levels of at least 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 may quarrel with your knife fish over the best hides, so provide more caves if needed.

Is the black ghost knifefish aggressive? In the right conditions, they can live in a community aquarium with other similar-sized, peaceful fish. It is not a good idea for tank mates to bully or outcompete them for food. Your adult knifefish will happily eat neon Tetras and any small fish it can fit into its mouth.

What fish will live with a black Ghost Knife? Many hobbyists keep adult BGKs in tanks that are larger than 6 inches (15cm) in size.

Two black ghost knifefish can live together? This is a common problem. Knifefish can be territorial and won’t share their space with other electric fish like 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 are the Black Ghost Knife Fish’s Favorite Foods?

They are easy to care for and can eat a predominantly carnivorous diet. They are a bottom dweller but will eat both floating and sinking fish food. Ours love worms, bloodworms and brine shrimp. They also like pellets and freeze-dried foods. Once they are old enough, they will predate upon small fish and other invertebrates.

Black ghost knives may be shy at first, and will spend the day hiding in their favorite spot until they are ready 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.

Are black ghost knife fish allowed to eat flakes? It is possible for them to be outcompeted by other species of fish when it comes down to 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 do your research well and are looking for a big tank to house it, the black ghost knivesfish might be the perfect pet. While we do not ship fish, check our preferred online retailers to see what they have in stock.