The cardinal tetra is a freshwater fish of the family Characidae of order Characiformes. It is native to the upper Orinoco and Negro Rivers in South America. Growing to about 3 cm (1.2 in) total length, the cardinal tetra has the striking iridescent blue line characteristic of the genus Paracheirodon laterally bisecting the fish, with the body below this line being vivid red in color, hence the name "cardinal tetra". The cardinal tetra's appearance is similar to that of the closely related neon tetra, with which it is often confused; the neon's red coloration extends only about halfway to the nose, and the neon's blue stripe is a less vibrant blue.
Cardinal tetra
The cardinal tetra (above) has more red on the underside than the superficially similar neon tetra (below).
A shoal of cardinal tetras in an aquarium
The Orinoco is one of the longest rivers in South America at 2,250 kilometres (1,400 mi).
Orinoquia Bridge near Ciudad Guayana, Venezuela
Orinoco in Mariusa National Park (Delta Amacuro)
Orinoco at its confluence with the Caroní River (lower left)
Rapids of the Orinoco, near Puerto Ayacucho airport, Venezuela