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. Unlike your average betta fish though, it is a considerably larger pet that requires a ton of room and may live for over a decade. Let’s discuss what it takes for this oddball fish to be happy and healthy long-term before you commit.

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. Common name “knifefish” is derived from its lack of a caudal or dorsal fin. This gives it a knife-like appearance. 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. Juveniles are often sold in large tanks where they may get into trouble with other fish. Make sure you get a healthy one with both white spots on the tail. Given that this fish can live as long as a pet dog, consider asking the store employee to feed them first so you can confirm your new knifefish is eating well before taking it home.

A healthy knifefish should be able to carry a lot of weight and have an active 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 can black ghost knife fish grow. We have seen them grow up to 20 cm (20 inches) the first year. Then, the growth rate slows to around 2 inches (5 cm) each year.

Is the black ghost knifefish hardy? Many people call them “sensitive” fish that don’t live very long, but that hasn’t been our experience. Our success is due to their excellent nutrition, keeping them safe, and making sure they aren’t picked on. 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 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 talk about 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 generally do fine with pH of 6.8-7.8, temperature between 75-82degF (24-28degC), and at least 5deg (90 ppm) GH. 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. To make sure they feel safe and secure in their shelters, increase the size of their tunnels and caves as they get bigger.

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

Can 2 black ghost knifefish live together? We don’t recommend it since problems tend to arise. 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 very easy to keep and they eat a mostly carnivorous diet. Despite being a bottom dweller, they willingly go after both floating and sinking fish foods. 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 can be a bit shy at first and want to spend all day in their favorite hiding spot until it’s time to eat. Therefore, many people have trained theirs to eat out of their hands or from the water surface by using 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 showpiece fish is such a fun and cool-looking species to own. The black ghost knifefish is a great pet if you’ve done your research thoroughly and are ready to buy a large tank. Although we don’t ship fish, please check our preferred online retailers for information about what they have.