Choosing a Knifefish

The knifefish is an unusual and beautiful fish that is sure to attract attention in your freshwater aquarium. Varieties of knifefish can be found from South America to Africa to Southeast Asia. They are a peaceful and shy fish that will need a long tank to show off their graceful swimming skills.

Appearance and Behavior

Knifefish are named because of their flattened and tapered appearance. It looks as if you could hold one by the tail and use it like a knife. The long fin on its underside waves continually, adding to its beauty. These fish are shy and hide during the day. They swim and feed at night, giving your tank 24-hour activity.

It's best to provide your knifefish with a hiding place for the daylight hours. A hollow log or plexiglass tube will do nicely or construct a deep cave. Knifefish have a weak electric organ at the base of the tail used for locating their food. Knifefish are reported to be peaceful most of the time, but are known to be aggressive eaters and can consume smaller tank mates.

There are over 20 varieties of knifefish but only 4 are popular aquarium fish. The black ghost knifefish is probably the most well known. The clown, royal and African knifefish can also be found in some aquarium shops.

Feeding and Tank Requirements

Knives are not fussy eaters. Bloodworms are their preferred food but most will accept flakes, pellets, beef heart or small live foods. They can grow quickly and range in size from 3 to 15 inches. Maintain water temperature between 72 to 82 degrees Fahrenheit, pH 6.0 to 7.5. Knifefish have been known to live for 15 years. Because of their physical characteristics, knifefish do best in a long tank. These fish will not thrive in hexagonal tanks or other types constructed for depth.

Special Concerns

Avoid combining knives with smaller tank mates that may be mistaken for food. Clown loaches, plecostomus, gouramis and corydoras catfish may be compatible.