The neon tetra (Paracheirodon innesi) is a freshwater fish of the characin family (family Characidae) of order Characiformes. The type species of its genus, it is native to blackwater or clearwater streams in South America, in particular the tributaries of the Solimões.

The neon tetra is light in color, apart for the characteristic Paracheirodon iridescent blue-green horizontal stripe along each side of the fish from nose to the front part of the tail and its prominent red coloration along the posterior half of the lower body. It grows to approximately 3 cm (1.25 in) in overall length. Sexual dimorphism is slight, the female having a slightly larger belly.

P. innesi is one of the most popular aquarium fish, having been bred in tremendous numbers for the trade.

The green and black neon tetras are distinct species (the latter belonging to an altogether different genus, in fact) and not color varieties. The cardinal tetra, also sometimes called the red neon, is a very similar species and is often confused with the true neon tetra. Hyphessobrycon innesi, on the other hand, is an obsolete synonym for P. innesi, the neon tetra itself.

In the aquarium

Neon tetras are considered easy to keep in a community aquarium. They tend to be timid unless hungry, and because of their small size they should not be kept with large or aggressive fish, who may bully or simply eat them. Mid-level feeders, they are best kept in schools of five to eight or more, for the "shoaling" effect when they move around the tank. Their color and the iridescent stripe may become dim at night, and they can be virtually invisible after a period of darkness.

While neon tetras bred commercially have adapted to a wide range of water conditions, in the wild they inhabit very soft, slightly acidic waters, between 20 and 26 °C (68–79 °F).

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