Aquariums at Home may earn an affiliate commission when you buy through links on this site. See footer.

How do You Breed Black Ghost Knife Fish?

Black ghost knife fish originate in the deep freshwater basins of the Amazon between Venezuela and Paraguay. All-black in color except for two white rings on its tail, this species is nocturnal and uses electrical receptors to detect prey in the water. If you’re thinking of keeping this fish, you may be wondering how to breed them?

Breeding black ghost knife fish in captivity is no easy feat. You must have optimal water conditions that replicate the ‘rainy season’ of the Amazon. An extra-large planted tank with plenty of driftwood and rocks for hiding places and egg deposition are a must. Breeding should be done by experienced hobbyists only.

Now that you know you need a very big aquarium with the appropriate water parameters for breeding black ghost knife fish successfully, let’s explore this topic further. I’ll explain how to setup your tank in advance, how distinguish the males from the females, how to introduce a mated pair to the aquarium, what to feed them, and how to rear baby fry.

So, if you’re ready to learn more about caring for, breeding, and rearing black ghost knife fish, then let’s begin!

Can You Breed Black Ghost Knife Fish?

You can breed black ghost knife fish in captivity, but it’s often difficult to do. As little is know about this species’ breeding habits in a contained aquatic environment, many aquarium hobbyists choose to purchase them from fish keepers that often spawn them in large breeding ponds rather than tanks.  Breeding black ghost knife fish requires an extra-large tank – at least 200 gallons per mated pair!

What Tank Size is Best for Breeding Black Ghost Knife Fish?

To breed black ghost knife fish, you’ll need a very large aquarium. Since a single ghost knife needs a 100-gallon tank to thrive in captivity, a 200-gallon tank for a male/female pair is your best bet. To increase your chances of successfully breeding this species, you must ensure the aquatic environment isn’t too small or overcrowded.

How to Setup a Tank for Breeding Black Ghost Knife Fish?

Setting up your tank properly is key to successful ghost knife fish breeding. Begin by laying a fine-grained substrate like sand along the bottom. Add plenty of plants and driftwood for cover. Since they originate in tropical freshwater conditions, ensure the parameters are appropriate – including a temperature of 72- to 82-degrees Fahrenheit, a pH range of 7-8 and a hardness between 0 and 10 KH.

Adding a tube to the tank is also a good idea. Successful ghost knife breeding is dependant upon a safe aquatic environment. If the female fish (in particular) feels secure in her surroundings, she’ll be more inclined to lay her eggs. Since this species likes hiding places, a PVC tube is great for reducing stress and provides an escape from too much light.

How to Induce Black Ghost Knife Fish Spawning?

Unfortunately, there are very few ways to induce spawning with this species. As black ghost knife fish like to breed at night, try keeping the aquarium in a quiet area, free of movement and with the light off for at least 14 hours each day. Consider adding extra floating plants, rocks, or other easily transferable decorations to serve as deposition areas for eggs.

Simulating the wet or rainy season in the aquarium may also help increase the likelihood of black ghost knife fish spawning. Start by reducing the water level in the tank gradually and leave it lower for a week or two. Then, slowly refill the tank again using cooler water and watch for signs of breeding. Afterwards, continue doing frequent 25-50% water changes.

How Can You Tell if a Black Ghost Knife Fish is Male or Female?

Ghost knife fish are often hard to sex, since males and females look very similar. This makes it difficult to establish a mated pair for breeding purposes. During the spawning seasons, males will often display a red color along their tails. As well, males tend to have larger eyes that are set higher on the head. Determining the gender of this species at a young age is next to impossible.

How to Introduce a Mated Pair of Black Ghost Knife Fish to an Aquarium?

Many aquarium hobbyists consider this to be the most difficult part of breeding black ghost knife fish. Purchasing an already compatible, mated pair is likely your best bet for successful spawning. For this, you’ll likely need to contact a professional breeder that specializes in this species alone. Doing research online in advance is strongly encouraged.

What to Feed Black Ghost Knife Fish to Encourage Spawning?

To encourage black ghost knife fish to mate, you must feed them appropriately. A nutritious diet comparable to what they’d eat in their natural habitat is recommended. Meat-based live or frozen foods like bloodworms and brine shrimp (offered at nighttime) are the perfect choice. Unlike other species of omnivorous freshwater fish, black ghost knife fish don’t transition well to flaked of pellet foods.

How to Care for Black Ghost Knife Fish Fry?

Caring for black ghost knife fish begins with careful observation of the tank during the ‘mating season’. Since this species is known to eat their own young, you must be vigilant in removing the eggs as soon as possible following fertilization otherwise, there’ll little chance of offspring survival.

Be sure to have a separate breeding tank – between 10 and 20 gallons in size – setup in advance with the correct water parameters, including a thermometer and a heater – for more information, please see above under the subheading entitled: How to Setup a Tank for Breeding Black if Ghost Knife Fish?

Take the rocks or pebbles that the eggs are attached to and place them gently into the breeding tank. Ideally, the depth of the water shouldn’t be more than 6 or 7 inches. Watch for signs of life as eggs should start to hatch within 4 to 5 days. Feed baby fry infusoria for the first week.

You’ll need to feed hatchlings up to 5 times daily to ensure their survival. After 7 days – when the babies are swimming freely about the breeder tank – you can offer them pieces of frozen brine shrimp that’s been thawed and cut small, followed by powdered flake foods.

Offspring can be introduced to the main tank with their parents once they’ve reached a length bigger than that the adults’ mouths. Pay close attention to how the fish are reacting to each others’ presence. If the tank is big enough to allow each to claim its own territory, you shouldn’t have a problem.

How to Make Infusoria for Black Ghost Knife Fish Fry?

To make your own baby fish food, follow the 10 simple steps outlined below:

  1. Purchase chopped lettuce or spinach – even shredded cabbage will work well.
  2. Fill a 1-quart jar about ¼ full with cut-up leafy green vegetables.
  3. Add boiling water to the halfway point on the jar.
  4. Allow the liquid to cool for 5 minutes.
  5. Pour in aquarium water to fill the jar.
  6. Seal the jar with a lid or place a cheesecloth overtop of it.
  7. Set the jar in a sunny spot near a window for 2 to 3 days.
  8. Take an eye dropper or turkey baster and dip into the middle of the infusoria liquid jar.
  9. Feed the fry up to 5 times a day for 7 days by squirting the liquid directly into the tank.
  10. Store the infusoria at room temperature and discard any leftover liquid promptly after 1 week.


To conclude, breeding black ghost knife fish successfully is a difficult task, even for the most experienced of aquarium hobbyists. Optimal water conditions with consistent 50% water conditions to replicate the ‘wet’ or ‘rainy’ season is a must. A 200-gallon planted tank with driftwood for hiding places and rocks for egg deposition is recommended.

I trust this article has answered your questions pertaining to ghost knife fish breeding and care. Thanks for reading and good luck with your aquarium hobby!

Recommended Posts

Ghost Catfish Care Guide: Tank Setup, Tankmates, Breeding, Diet

When is Breeding Season for Goldfish?

How to Breed Kissing Gourami Fish?

Will Mollies and Platies Breed?

What is a 40 Gallon Breeder Tank and why you might want one

What Do Guppies Need to Breed?

Elephant Nose Fish Care Guide & Tank Setup (Behavior, Tank Mates, Breeding, etc.)