Comments: These are fabulous looking fish mostly dark, almost black with white markings and the unique knifefish shape and unique fin motion when swimming.

Origin: their ancestors lived in a vast area in South America from Venezuela in the north to Peru in the west then farther south and east to Paraguay.

Maximum Size: In aquariums, this Knifefish is rarely seen bigger than 10" long, but it can grow to be more than 15" long and sometimes larger if kept in excellent water and fed properly.

Behaviors: a Knifefish swims by undulating the long fin along the underside of its body. It's rather startling to see them swim backwards and forwards with equal ease.

It's also 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 that these Knifefish will 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 these Knifefish think their hidden.

Of course human eyes can see inside the clear tube, like the one shown just below.

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

Compatibility: Some recommended tankmates include larger Tetras, Corydoras Catfish, Plecostomus, and Silver Dollars that are all too big to fit into the Tiger Knifefish's mouth.

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 Tiger Knifefish.

Tiger 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 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 their electric fields expand and allows 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.

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 80-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.

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: There are no known reports of this Knifefish breeding in captivity.

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 Tiger Knifefish is Gymnotus species.

Variations: We know of no variations.

We hope you've enjoyed reading these comments.

DrT - 12/12/2014