If you’re looking for a fish with some serious wow factor, you would be hard-pressed to pass up the Black Ghost Knifefish (Apteronotus albifrons).
Also known as the Apteronotid Eel, Black Ghost, and Black Knife, this fish is intriguingly different and distinct from most inhabitants in any given hobbyist’s tank.
This is a tropical freshwater fish that looks quite unlike any other, and they come from the South American basins of the Amazon.
Truth be told, they are actually quite spooky to look at, which is perhaps where they gained the name Ghost in their commonly used moniker.
With an unusual morphology, unusual convex shaping, and eerie looks, this is fish that will undoubtedly captivate any tank observer. So unique are they in their appearance, they do hold some serious appeal and have been popular for a long time in the trade.
They have some real quirks, too, which make them ideal for someone looking for something completely different. Just be sure you have access to some seriously ample tank space to go with that instinct if you decide to get one. They are huge when they reach full maturity.
Let’s unlock the details about this fish that make it such a satisfying acquisition for the hobbyist who thinks they’ve seen it all (who has adequate accommodation).
Black Ghost Knifefish Behavior
Black Ghosts are rather peaceful fish who go about their day doing their own thing and not getting into any other community member’s way.
This is a good thing because, at full size, these fish are massive, and you wouldn’t enjoy seeing one of these fish be aggressive towards others.
They are nocturnal and will display little activity during the day. When they do venture out, they are usually seen swimming openly, spending some time hiding in vegetation, and looking for food in the substrate.
If you should be so fortunate as to have a gigantic tank suited to housing more than one of these fish, you should be prepared for some territorial aggression. If the tank isn’t suitable large enough, they will battle for turf, and you’ll have a turf war on your hands.
Most hobbyists are able to manage just one Black Ghost because of their size.
Fun Fact: These fish get the name Ghost in their name, not because of their eerie, floaty looks, but because natives to the tribes of the Amazon believe that departed souls inhabit these fish in spirit.
In reality, they are mesmerizing to watch with their swimming action. They also use electric pulses to locate where they are, find food sources, and guide them in the murky waters of the Amazon in the wild.
A relative of the Electric Eel, their electric field pulses are completely harmless and quite weak by comparison.
Black Ghost Knifefish Lifespan
If you cater to the needs of your Black Ghost Knifefish, you could expect them to live for around 10 years, but they have been known to reach 15 years. This is a considerable amount of time, so a fair amount of commitment.
We will discuss more on tank requirements a little later in this article.
Black Ghost Knifefish Appearance
The name of this fish is rather descriptive of their appearance.
Are they black? Yes.
Are they shaped like a knife? Yes, with their anal tail being ringed in white, making it look like a handle.
Are they ghosts? Well, erm, no. But they do have some ghostly qualities! Their eyesight is poorly developed and looks whitish, giving them that aforementioned eerie look.
They do not possess dorsal or caudal tails, which is unusual for fish. Their convex-shaped bodies are flat and long, curved on the topline, which tapers to a tail shape at the rear. They also have blunt round noses.
When fully mature, the reality of the size of these fish becomes apparent as they can reach 20 inches in length.
Their swimming action looks like that of a ray or flying fish as the body yields to wing-like sides that billow and ripple as they move and glide through the water.
Like catfish, Black Ghosts do not have any scales for armor and instead have soft skin that is coated in mucus for protection. This means they are more susceptible to disease, injury, and water parameters.
Black Ghost Knifefish Habitat And Tank Requirements
For the more experienced hobbyist, these fish will still present a challenge to keep well, given their size and structure.
They need a lot of space, and unfortunately, too many unscrupulous traders have pawned these fish off to unsuspecting buyers under the premise that they will only grow to fit the tank. This is absolutely not the case and has led to a plethora of early deaths or unwanted fish.
So you do need to be certain you can accommodate such a unique creature and that you are capable of being quite strict about your water condition to ensure optimum health for these amazingly unique creatures.
Tank Conditions
Unsurprisingly perhaps, Black Ghosts are sensitive to water parameters, so if regular cleaning and testing isn’t the name of your game (and why would you have a huge tank if that was the case), then perhaps these fish aren’t for you.
In the wild, they live in quite murky waters that are muddy and cloudy, which is why they rely on their electric pulse methods for navigating and finding food.
Substrate for these fish must be soft to avoid any injury or scratches when these bottom feeders eat or search for food. Extra fine sand or gravel is best in this instance.
Much of the usual aquarium fare fits in well here like smoother rocks, driftwood, caves (which would have to be large), as well as the usual suspects for plant life.
Great plants to include would be Java Fern, Amazon Swords, Hornwort, and Java Moss.
Strong filtration is a good idea as these fish create a lot of waste.
Water changes will need to be weekly and at least 25% changed over.
Water conditions should be noted and maintained as follows:
- pH of 6.5 – 8.0
- Water hardness between 5 – 19 dGH
- Temperature between 73 – 82ºF (23 – 28ºC)
- Lighting should be on the lower end of the scale to encourage them to come out and play
Tank Size
The minimum tank size for a single Black Ghost Knifefish is 100 gallons, and you’ll need to up that size by 80 – 100 gallons for each additional fish you may wish to include.
Choosing a long tank size is best to encourage active swimming, but ensure it is also wide enough so they can comfortably turn around.
Choosing Tank Mates For Black Ghost Knifefish
If you acquire one, find out if it’s wild-caught or captive-bred. If it’s wild, you’ll need to quarantine to ensure no foreign bacteria messes with your well-cycled tank.
What you need to avoid is anything of a similar size that will bring out their aggressive side. Avoid other Knifefish that bears a similar shape, or that can spark their interest in becoming aggressive too.
Fish that aren’t aggressive and are a little bit smaller without looking like a meal are your best bet, around 10 inches in length.
Some tank mate pairings that really would work well include:
- Catfish species
- Tetras (when juveniles)
- Rope Fish
- Bichir
- Oscar Fish
- Silver Dollar Fish
- Electric Blue Acara
- Other large peaceful Cichlids
- Discus
- Corydoras
- Angelfish
It’s also probably best to avoid smaller crustaceans and snails who will be snapped up as live food.
How To Feed Black Ghost Knifefish
Black Ghosts are carnivorous micro-predators who enjoy live prey, which makes the issue of live prey feeding somewhat easier to handle.
They love eating larvae, insects, smaller fish, and worms in their native habitat. In the home, you can add in bloodworms, tubifex, and brine shrimp in frozen or live formats.
If you happen to have wild-caught Black Ghosts, they will take some time to adapt to pellet or flaked foods.
Ideally, you’ll need to be offering food at night when they naturally hunt, and they should finish eating in around 5 minutes, or else you’re overfeeding them.
Their shy nature can mean they can take some time when newly introduced to settle into a regular feeding schedule. Over time, however, some owners report that these gentle giants will actually hand feed!
Common Health Issues Of Black Ghost Knifefish
Most freshwater fish are susceptible to Ich (White Spot Disease), which, as the name implies, is easily distinguished by white spots on the body due to a parasitic infection.
Ich is treatable when caught early and suitably medicated. If left untreated, Ich is usually fatal.
Their extra-sensitive skins that are scaleless render them more susceptible to disease and health issues than their scaled cousins.
Thankfully, their black coloring allows owners to spot abrasions or the white spots of Ich easily.
If you need to medicate these guys, you must avoid anything copper-based as it will poison them.
A lot of these issues are to do with water conditions or poor nutrition.
Having water testing kits and a UV sterilizer will go a long way to assisting you in keeping your fish healthy.
These issues are minimized with a strict water cleaning and change schedule and regular checking of your water parameters. Remember, your tank is a living biome, and it isn’t just fish living inside it. Bacteria and parasites must be managed to acceptable levels.
How To Breed Black Ghost Knifefish
The likelihood of breeding Black Ghosts Knifefish is extremely unlikely. Not least because most people manage to house just one, but having two properly sexed requires a massive amount of space.
Most available in the trade have been commercially bred in huge facilities, but for the average hobbyist out there, there isn’t a wealth of information at large.
On top of this, apparently, pond breeding is the most reliable way to attempt breeding them, but in addition, they need to be bonded, have perfect water conditions, dimly lit quiet surroundings, and somewhere else to remove the parents to, if you achieve spawning.
So not much needs to be on your side then! Best left to the professionals.
Are Black Ghost Knifefish A Good Idea For Your Aquarium?
What is certain is that these fish will have you hooked in no time. They are so unusual in their looks, shape, and swimming action, they can be quite hypnotic to watch as they float and flutter through the tank space.
Their massive size will look impressive, but their docile nature will mean they are nothing to be too wary of in terms of tank cleaning and handling when required, which is a way of saying their kind character and charm go a long way.
Because of their delicate skin and sometimes tricky nature to feed, we still recommend that more experienced hobbyists take on these extra-large water blades.
They are certain to be a conversation piece in your home and make for a real showstopper taking pride of place in the hearts of their owners.
If you can manage to get one to feed from your hand, they will truly feel like a more traditional pet which is always a special thing for this hobby as it’s quite rare.
Despite their foreboding, spooky name, the Black Ghost Knifefish isn’t some back alley assassin attempting to mug anyone.
They just want to drift around at night peacefully in their inimitable style.
And there’s nothing sinister about that.
