Behaviors: a Knifefish swims by undulating the long fin along the underside of its body.

It's rather startling to see one swim forwards and then backwards with equal ease.

A Black Ghost is usually nocturnal and hides from the light during the day.

But it's very smart and can be coaxed to eat from your fingers.

There are special clear plastic tubes for these Knifefish to hide in, or at least they think they're hidden.

They sense their environment with an electric field that surrounds their bodies, and that field does not penetrate the plastic tube, so a Knifefish inside a clear plastic tube will think it's hidden.

Click here or on the picture, just above, to learn more about Lee's Ghost House.

Knifefish may seem to be OK with small fish like Neon Tetras during the day.

But the Neons usually disappear at night and are most likely eaten by the Ghost Black Knifefish.

Black Ghost Knifefish usually do not get along with each other even in a very large aquarium. So it's best to keep just one in an aquarium.

Fish that are very aggressive, like some Cichlids, will probably harm these Knifefish.

Click here to read more about compatible groups of pet fish.

Temperature: Knifefish live best from about 75 to 80-degrees F. with 78 being perhaps ideal.

Click here to learn about aquarium temperature, aquarium thermometers, and aquarium heaters.

Feeding: we feed them small Premium Pellet Food here in our aquariums. So you should continue feeding them that same food.

But sometimes after being shipped they won't eat, and you may have to feed them small fish, Ghost Shrimp, and live Black Worms for a while, before you can coax them into eating pellets again.

Click here to learn more about and shop online for premium fish foods.

Water Conditions: since these fish live across a wide area, apparently they can adapt to a wide range of water conditions.

But our deceased and long-time friend Dr. Walter Heiligenberg, who was an expert in weakly-electric fishes, like these Black Ghost Knifefish, and who had made several trips to South America to study weakly electric fishes and many other subjects, told us these Knifefish live best in black water, which has a low pH and a low concentration of ionized minerals.

In black water with very low concentrations of minerals their electric fields expand, and the bigger fields allow them to better sense their environment.

The water in our aquariums is not black water, and it has a pH of about 7.8 with a high concentration of ionized minerals.

These Knifefish seem to do well for us in this water, and we ship them in this water.

But their aquarium water should gradually be converted to rain-like water eventually.

Click here for a lot more information about aquarium water conditions.

Aquarium Size: Knifefish will do fine in an aquarium with at least 50-gallons of water when small but will eventually need to live in an aquarium with at least 150-gallons of water.

Decor: Knifefish do not need gravel, and a layer of gravel more than 1/4" thick will usually fill with bits of uneaten food that will contaminate the water.

Click here for more about aquarium gravel.

Live plants are beautiful and improve the water quality. Knifefish love to live among the live plants. Perhaps they really need to live among live plants.

Aquarium Filter: Bio-Wheel Filters are highly recommended.

A 50-gallon aquarium needs one or two Penguin 350B Filters.

Most 80-gallon aquariums have room along the back for at least two Penguin 350B Filters.

Better is a 120, 150, or 200-gallon aquarium with as many Penguin 350B Filters as will fit across the back.

Click here to learn more about aquarium filters.

The addition of Lava Rocks will keep nitrates in the ideal range.

Click here to learn more about using Lava Rocks in aquariums.

Life Span: Knifefish can live for several years.

Keep the water conditions excellent and feed them premium foods, and they may live even longer lives. Maybe as long as 20-years.

Gender: It's difficult to tell males from females. But presumably mature females become plumper, as they fill with eggs.

Breeding: These Knifefish have been bred in captivity by our suppliers who breed them, and then send them to us.

Click here for a lot more about breeding various tropical fish in aquariums.

Popularity: These fish are rare but somewhat popular in the hobby.

Names: The scientific name for Black Ghost Knifefish is Apteronotus albifrons.

Variations: We know of no variations.

But they occur across a vast area, so we suspect that there are variations that have yet been distinguished by scientists.

We hope you've enjoyed reading these comments.

DrT - 12/12/2014

Email Comment: "This kind of fish, so easy to die "

Our Reply: Thank you for your comment.

This fish is more difficult than average to keep in aquariums, because the water in their natural environment is quite different than the water in most aquariums.

The ancestors of the Black Ghost Knifefish inhabited the the black water rainforests of South America.

Black Water is very unique and most of the fish originating from black water are difficult for most aquarists to keep and care for.

Black waters occur where there is a lot of rainwater that has not yet dissolved minerals from the ground and rocks.

As a consequence black water is almost always low in pH.

Say, from about 5.0 to 6.5, but occasionally during the year the pH may go higher.

Also a large amount of chemicals have dissolved from the vegetation into the water, which turns the water black.

So black, that hands and feet cannot be seen a few inches below the surface of the black water.

So eyes like ours and most other kinds of fish, can't see much of anything in black water.

Fish that live in black water almost all have much smaller eyes and have adapted to sensing their black water environment in another way.

A Black Ghost Knifefish senses it's environment by emitting electromagnetic waves from it's tail and receiving the signals in small pits in it's body.

The frequency of these waves, which unlike light waves, does penetrate through the black water, and allows the Black Ghosts to sense their environment.

Black Ghosts are rather aggressive to each other. When quarreling they often nip at each others tails and by doing so can "blind" one another and then are not able to find food.

They also grow quite large. I once saw one about 16" long, and I believe they grow a few inches bigger.

So an aquarist must prepare to eventually provide a large aquarium with at least 150-gallons.

It's also often difficult to feed Black Ghosts.

Their ancestors ate only live foods like worms, insects, and small fish. But we've found that they can be trained to eat the highest quality pellet foods.

Some aquarists do not know this or ignore it, and so their Ghosts do not get proper feedings.

A Black Ghost will do better in an aquarium with live plants in water with low pH and low iconic content, which is similar to the rain-like water in the waters in which their ancestors lived.

Because of these and other factors, they are not so easy to keep, and so not a good fish for most new and inexperienced aquarists.

But of course they are really interesting with an undulating swimming fin and being able to sense their environment through opaquely black waters.

Conclusion: Black Ghost Knifefish require an environment that is different than most aquarists can provide, including live food, live plants, and rain-like water.

Thanks again for your comment.