Silver Tetra Oligosarcus

Oligosarcus argenteus is a sleek, torpedo-shaped piscivore from the río de la Plata drainage and adjacent Atlantic coastal river systems of eastern South America. Reaching around 20 cm, it has a bright silver body with a faint midlateral stripe and a large, toothy mouth designed for seizing small fish. It belongs to the subfamily Stevardiinae and is a fast, active hunter that in the wild targets schools of smaller tetras and characins.

In the aquarium, Oligosarcus argenteus requires at least 250 litres with clean, moderately cool to warm water and good oxygenation. It is a fast swimmer and appreciates open water lanes. Being from a subtropical drainage, it tolerates temperatures down to about 18–20°C, making it an option for unheated cooler setups in temperate climates. All fish small enough to be eaten will be targeted.

Feeding is straightforward once settled — frozen or fresh fish strips, frozen prawns, and eventually carnivore pellets are accepted readily. It is less demanding in captivity than cynodontid relatives and is a feasible if challenging choice for intermediate-to-advanced aquarists interested in predatory South American characins.

Water: Moderately soft, pH 6.0–7.5, 18–26°C; tolerates cooler subtropical temperatures. Tank: 250 L minimum; open water; secure lid; no small tankmates. Feeding: Carnivore — frozen fish strips, prawns, carnivore pellets; accepts prepared foods well. Breeding: Not documented in home aquaria. Compatibility: Aggressive piscivore toward smaller fish; best solo or with very large non-swallowable species.