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Glass Knife Fish

Green Knife Fish Family: Sternopygidae

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Glass Knife Fish Eigenmannia virescens Photo © Animal-World: Courtesy David Brough

   The Glass Knife Fish has a peaceful shy demeanor, it does best if kept in the company of its peers.

   Coming up with common names for aquarium fish can be difficult at times. Trying to find a catchy name that distinguishes one fish from another is not always an easy task but occasionally a fish comes along that makes the naming job easy. Eigenmannia virescens is one of those fish because it is semi-transparent and shaped like the blade of a knife, hence the common name of Glass Knife Fish.

   Glass Knife Fish are unusual, even for knife fish. Their bodies are relatively stiff and because their fins and much of their bodies are transparent, they appear to be jet propelled because it can be difficult to see the rippling anal fin which provides their means of locomotion. They are non-aggressive and are also quite timid, doing best when kept in a large species tank with their own kind. Though they will develop a hierarchy of dominant and submissive fish, they will not injure each other.

For more Information on keeping freshwater fish see:
Guide to a Happy, Healthy Freshwater Aquarium

Distribution:
   The Glass Knife Fish was described by Valenciennes in 1836 .This species of knifefish is found throughout the Amazon River basin in South America, inhabiting freshwater flood plains, ponds and creeks where the substrate has lots of plant detritus. Most specimens offered for sale are exported from Colombia.

Status:
   The species is not listed on the IUCN Red List.

Description:
   The semi-transparent body of the Glass Knife Fish, occasionally with a tint of green, is flat and elongated. They don't have a dorsal fin or a caudal fin, but there is a continuous fin along the underside that moves with an undulating motion. It can be difficult to see this rippling anal fin which provides their means of locomotion. Because their bodies are relatively stiff and their fins and much of their bodies are transparent, they appear to be jet propelled.

Size - Weight:
   The maximum size for a female is about 8 inches (20 cm) and males are said to grow to as large as 17 inches (45 cm).

Care and feeding:
   The Glass Knife Fish are carnivores. Their feed should consist of smaller sized fresh or frozen foods such as bloodworms, brine shrimp or blackworms.
   These are a fish that will do best in groups of 5 or more. Even with a small group, they can appear to be shy. This is because they are naturally nocturnal so they are not usually active during daylight hours. Make they feel secure by giving them plenty of hiding places by providing their home with plants, wood and smooth rocks. Once they become accustomed to living in an aquarium, they will become more outgoing, especially at feeding time.

Water Region: Top, Middle, Bottom:
   Glass Knife Fish will generally stay near the bottom where there is cover for them to hide and feel safe.

Acceptable Water Conditions:
   Temp: 68 - 86° F (20 - 30° C)
   Hardness: 2 - 15 dGH
   pH 6.0 to 7.0

Social Behaviors:
   Most knifefish are known as stealthy predators with relatively large mouths but Glass Knifefish are an exception to this generalization. They are predators but their mouths are relatively small so they will not eat your other pet fish unless they are very, very small. The Glass Knife Fish are timid and non-aggressive.

Sexual Differences:
  Males grow to be much larger than the females.

Breeding/Reproduction:
   Glass Knifefish have reportedly been spawned in captivity although this is not a common occurrence and the details are sketchy.

Buy Glass Knifefish From LiveAquaria.com

Practicalfishkeeping.co.uk reports that knifefish were spawned by using the following method: The water level in the tank was raised and the pH and water temperature were lowered to simulate a rainstorm. 100+ eggs are laid on floating plants where they are fertilized by the dominant male.

Availability:
  Glass Knife Fish are commonly available.

Author: Ken Childs

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Latest Comments
I just bought one of these fish, and it seems to get along with all of my fish, even my pictus cat. It is an interesting fish but does seem a little shy. Matt 2008-12-09

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