HomeFreshwater aquarium fishOddballs & predatorsGlass knifefish Glass knifefish (Eigenmannia virescens) Scientific name: Eigenmannia virescens Valenciennes, 1836 The Glass knifefish (Eigenmannia virescens) is a freshwater fish of the family Sternopygidae that grows to about 35 cm (14 in). It is difficult to keep and aggressive, is best kept in a species tank and needs a tank of at least 210 L (55 US gal), water at 23–28°C (73–82°F) and a pH of 6.0–7.5. Native range: South America, Widely distributed east of the Andes from the Orinoco to the La Plata River basins. Glass knifefish care at a glanceCare levelDifficultTemperamentAggressiveCommunity tankNot suitableAdult size35 cm (14 in)Minimum tank210 L (55 US gal)Temperature23–28°C (73–82°F)pH6.0–7.5Hardness2–15 dGH (36–268 ppm)DietCarnivore. Accepts live foods. BiologyKnown to be gregarious, timid and nocturnal. Prefers deep still waters. Found in ponds and creeks with a substrate rich in plant debris. This gymnotiform fish can be found in colder waters of 18?C. Electric organ discharge (EOD) frequency cues have been experimentally shown to play a role in species and sex recognition in this species. Playback of a conspecific male's electric courtship display elicited spawning in ripe females. Diel rhythmic change in EOD may be manifested by the increase in EOD amplitude at night among dominant breeding males as they compete with other conspecifics. A fractional spawner; fecundity reported at 905 eggs. Males reportedly reach 45 cm TL, females to 20 cm TL.Source: FishBase, licensed CC BY-NC 4.0. Species factsScientific nameEigenmannia virescensFamilySternopygidae (Glass knifefishes)OrderGymnotiformes (Knifefishes)ClassActinopterygii (Ray-finned fishes)Maximum length35.8EnvironmentFreshwater;; pH range: 6.0 - 7.0; dH range: 2 - 15 benthopelagicClimateSubtropicalDistributionSouth America: widely distributed east of the Andes from the Orinoco to the La Plata River basins.Conservation status (IUCN)Not EvaluatedThreat to humansHarmlessUsesFisheries: of no interest; aquarium: commercialResilienceMedium, minimum population doubling time 1.4 - 4.4 years (Fec=40-160 (per batch)) More oddballs & predatorsBlack ghostApteronotus albifronsAmazon leaffishMonocirrhus polyacanthusGangetic leaffishNandus nandusZig-zag eelMastacembelus armatusApteronotus leptorhynchusEel LoachPangio anguillarisSee all oddballs & predators Can it live with...?Glass knifefish and African bonytongueGlass knifefish and Amazon leaffishGlass knifefish and Black ghostGlass knifefish and Eel LoachGlass knifefish and Elephantnose fishGlass knifefish and Freshwater butterflyfishGlass knifefish and Gangetic leaffishGlass knifefish and Indonesian snakeheadGlass knifefish and Lesser spiny eelGlass knifefish and PirapatingaGlass knifefish and Zig-zag eel SourcesTaxonomy, distribution and biology data: FishBase (Froese, R. and D. Pauly, eds.), licensed CC BY-NC 4.0. Aquarium care parameters compiled, checked and converted to metric and imperial units by Guppies.za.net.Last updated 28 September 2026