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 first discuss how to keep this unusual fish happy and healthy over the long term.
What is a Black Ghost Knifefish, you ask?
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”. 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. 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. 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.
What size can a black ghost knife grow to? It is possible for them to get quite large if they are fed enough. Don’t be surprised when your baby knifefish grows into a 14-to-18-inch (35-45cm) monster.
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.
Does the black ghost fish live long? We haven’t found them to be very hardy. 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. Usually, fish can handle one stress factor, but multiple stress factors will increase the likelihood of health issues.
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. 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 system allows the knifefish to locate prey and communicate with potential mates.
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. To make sure they feel safe and secure in their shelters, increase the size of their tunnels and caves as they get bigger.
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 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 will not share their space with other electricfish like baby whale fish or elephant nose fish. 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 will happily eat both sinking and floating fish, despite being bottom dwellers. Ours love worms, bloodworms and brine shrimp. They also like pellets 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 trained their black ghost knives to eat off their hands, or from the water surface with floating foods.
Black ghost knives are able to be trained to swim to the surface and eat directly 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. The black ghost knifefish is a great pet if you’ve done your research thoroughly and are ready to buy a large tank. While we do not ship fish, check our preferred online retailers to see what they have in stock.