All fish / Sternopygidae

Glass Knifefish

Eigenmannia virescens

Also known as green knifefish, transparent knifefish, glass knife fish, grass knifefish, eigenmannia, ปลาไนฟ์แก้ว, グラスナイフフィッシュ, ikan pisau kaca, 玻璃飞刀, 透明飞刀

A slender, semi-transparent knifefish with a pale pinkish-silver body and a long rippling anal fin that lets it glide forwards and backwards with ease. It produces a weak electric field for navigation and communication, and is kept for its graceful movement and calm, social nature.

Care at a glance

Care level

Moderate

Temperament

Peaceful

Adult size

20 cm

Temperature

23 to 28 °C

pH

6 to 7.5

Smallest tank

200 litres

Keep as

Group of 4 or more

Diet

Carnivore: bloodworm, brine shrimp, daphnia, small insect larvae and sinking pellets

Swims

Middle of the tank

Lifespan

8 to 10 years

Water

Freshwater

Wild range

Widespread in South America: Amazon, Orinoco, Paraná and Guiana basins

Breeding

Spawning has been achieved in captivity by simulating a rainy season with gradual water changes and falling conductivity, after which eggs are laid among plants. It is rarely bred in home aquariums and is considered challenging.

Good to know

Mostly nocturnal and shy, so it needs dim lighting, plenty of cover and peaceful tankmates; small fish such as neon tetras may be eaten by large adults. Males can grow larger than the typical 20 cm, sometimes over 30 cm.