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

This care guide is often requested by people because knifefish are unusual looking curiosities. They have an undulating fin which allows them to swim forward and backward. There are many types of knifefish available, but the black ghost knife (BGK), is the most common and sought-after. 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 first discuss how to keep this unusual fish happy and healthy over the long term.

What is Black Ghost Knifefish?

Apteronotus albifrons, a South American nocturnal sea fish with weak eyesight, uses electrical signals instead 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. 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.

Most black ghost knifefish are captive-bred nowadays and may cost $15-20 or more, depending on the size of the individual. Many times, juveniles are sold in crowded tanks and may get into scrapes with other fish, so make sure to get a healthy one that has both of the white spots on its 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 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. The keys to our success include feeding them really well, making sure they don’t get picked on, and maintaining good water quality, as you would with any other fish. Fish can usually handle one stress factor but health problems are more likely if there are multiple stress factors.

A ghost knife fish can shock you. It is a weakly-electric fish. This contrasts with a strong-electric fish like the electric eel, which can stun its prey. A knifefish’s electric organ generates a weak electricity field. It also has other sensing organs which can detect slight distortions in this field. These organs are similar to radar systems. 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 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. Tank mates should not bully or outcompete them for food. This includes aggressive cichlids and 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.

Can two black ghost knifefish live together It is not recommended as problems can 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 does the 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. Ours enjoy a variety of worms, bloodworms, brine shrimp, pellets that fit in their mouths, and freeze-dried foods. As mentioned before, they will predate on small fish and invertebrates once they’re old enough.

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 taught their black ghost knives to eat from their hands and the water surface using floating food.

Black ghost knives are able to be trained to swim to the surface and eat directly from your hand.

Do black ghost knife fish eat flakes? Flake food may not be nutritionally dense enough for knifefish in the long run, especially since it is easy for them to get outcompeted for food by other fish. We prefer to feed our fish pellets, freeze-dried, or frozen food to maintain a healthy weight.

This fish is an amazing showpiece and is so fun to own. 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. While we do not ship fish, check our preferred online retailers to see what they have in stock.