Neon tetra

The neon tetra (Paracheirodon innesi) is a small freshwater fish from the Amazon basin in South America. It belongs to the family Characidae, and its vivid colors help it stand out to other neon tetras in the dark, acidic blackwater streams it inhabits, and this same brightness has made it a favorite among aquarium keepers worldwide. These fish are found in the western and northern Amazon basin, spanning parts of southeastern Colombia, eastern Peru, and western Brazil. They prefer acidic blackwater streams but also live in clearwater streams, avoiding whitewater rivers entirely.

Description

Water temperatures in their natural habitat range from 20 to 28 °C (68–82 °F), with a pH between 4 and 7.5. The neon tetra has a light-blue back and a silver-white belly. A bright, iridescent blue stripe runs horizontally from its nose to the base of the adipose fin on each side, while an iridescent red stripe starts at the middle of the body and extends to the base of the caudal fin. The rest of the fish, including its fins, is partially transparent.

Males and females look similar, but females have a slightly larger belly and a bent iridescent stripe, whereas males have a straight one. At night, the blue and red stripes turn gray or black as the fish rests, then regain their color in the morning. This change happens because guanine crystals in the fish’s cells reflect light differently depending on lighting conditions: in light, the stripe appears blue-green; in darkness, it shifts to indigo.

Economics

The fish grows to about 4 cm (1.6 inches) in total length. First imported from South America and originally described as Hyphessobrycon innesi by ichthyologist George S. Myers in 1936, the neon tetra was named after William T. Innes. It is one of the most popular aquarium fish, with roughly 2 million sold in the United States each month. Most of these are imported from Southeast Asia, where they are farm-raised, though some are still collected from the wild in Colombia, Peru, and Brazil.