• Scientific name: Eigenmannia virescens
• Synonyms: Cryptops humboldtii, C. lienatus, C. virescens, Eigenmannia lineata, E. humboldtii, Sternarchus virescens, Sternopygus humboldtii, S. lineatus
• Common name: Glass Knife Fish, Green Knifefish
• Group: Other fishes
• Habitat: South America;
• Size: Male: 45 cm, female: 25 cm
• Biotope: Found in freshwater flood plains from Rio Magdalena to Rio de la Plata, usually in strong-flowing streams.
• Social behavior: A nocturnal, timid yet gregarious fish. A group will form a rigid social structure with dominant and subdominant members. The fish recognize each other and will not inflict injury. They are best kept in a species tank.
• Diet: Carnivorous; all types of live foods; Tubifex, mosquito larvae, small crustaceans, snails, small fishes.
• Breeding: Very hard
• Tank: Minimum 250 litres
• Population: 5 fish for 300 litres
• Decoration: Use moderately fine gravel. Plants are not essential, though a floating cover will create welcome shade. Add hiding places among rocks and roots.
• Temperature: 23-28 °C
• pH: 6-7.5
• Hardness: 2-15 NK°
• Lifespan: 6 years

Description: Eigenmannia virescens have neither dorsal nor caudal fins. The anal fin has about 240 rays. The body is transparent, usually light green colored. The backbone can be seen through the body. Two fine, lateral stripes run along the body, the first runs on the base of the transparent anal fin, the second is just above this stripe. The head is brown. The fish are sensitive to fresh water and you should always use a good water conditioner when making water changes. During spawning, the Glass Knife Fish emits electrical signals.

Breeding was only recently successful. For breeding use low electrical cunductivity water, with a drop in pH. Increase the water level, and imitate the rainy season. The fishes spawn in the early morning hours. The dominant male, nearly always the larger, spawns with the rutting females. The eggs are tacky, a few being laid at each pairing on floating plants if they are available. Depending on the size of the female, 100 to 200 eggs are laid per session. A pairing lasts for several hours. Remove eggs and transfer them to rearing tank. Raise the fry on Artemia nauplii.