Buenos Aires tetra

The Buenos Aires tetra is a robust, active characid from the subtropical and temperate waters of southern Brazil, Paraguay, Uruguay, and northern Argentina. It is named after the capital city of Argentina, though its natural range extends well beyond that region. Unlike many of its tropical relatives, this species inhabits waters that experience cooler winters and abundant rainfall, giving it remarkable tolerance for lower temperatures. It reaches about 5–6 cm in standard length and is distinguished by its silvery body, reddish fins, and a black marking on the dorsal fin.

These tetras are undemanding but need plenty of swimming space. An aquarium with base dimensions of at least 90 cm x 30 cm (~81 litres) should be considered the minimum. Filtration does not need to be particularly strong, though they appreciate a degree of water movement. They are adaptable across a wide range of conditions — temperatures from 16–28 °C, pH from 5.5–8.5, and hardness up to 357 ppm. However, they should not be maintained at the upper end of the temperature range for extended periods as they are naturally a subtropical species.

Buenos Aires tetras have a reputation for nipping the fins of tankmates, especially when kept in insufficient numbers or cramped conditions. A group of at least eight to ten specimens is recommended, as the fish form loose hierarchies and rival males continually compete, creating a natural distraction. They are not ideal companions for shy, slow-moving, or long-finned fish. Their diet is omnivorous — they accept most foods and benefit from plant or algal content in their diet. Live and frozen foods supplement their nutrition and enhance colouration.