The best companions for neon tetras are other tetra species. The rummy-nose tetra (Hemigrammus rhodostomus) has silvery to iridescent greenish scales and is rarely longer than 2 inches. The cardinal tetra (Paracheirodon axelrodi), which is about 1.2 inches long, features blue neon stripes and a red belly. Other ornamental small tetras include the glowlight tetra (Hemigrammus erythrozonus) and the bleeding heart tetra (Hyphessobrycon erythrostigma).
Platyfish refers to two species of the genus Xiphophorus: the yellowish southern platyfish (X. maculatus) and the variatus platyfish (X. variatus). They can live peacefully with neon tetras, when in small schools. Like platyfish, other small fish of the family Poeciliidae, such as mollies and guppies, are also compatible with neon tetras. The guppy million fish (Poecilia reticulata) has a bright green body with yellow and black markings, while the Yucatan Molly (Poecilia velifera) is golden orange and can reach up to 4 inches in length.
Although generally larger than tetras, catfishes are bottom-feeders or scavengers and do not pose a threat to neon tetras. Popular catfish species for an aquarium include members of the genus Corydoras, often called cory catfish; the suckermouth catfish (Hypostomus plecostomus), which is often sold when small and young but can grow more than 1 foot in length; and catfish of the genus Physopyxis, which are about 1 inch long.
Rasboras are fish of the genera Microrasbora, Rasbora, Boraras, Trigonostigma, which are part of the carp family or Cyprinidae. Popular species in the market that make good companions to neon tetras include the harlequin rasbora (T. heteromorpha), the glowlight rasbora (T. hengeli), and the pink-and-violet lambchop rasbora (T. espei), which has a lamb-chop-shaped mark on each side.