The black neon tetra (Hyphessobrycon herbertaxelrodi) is a freshwater fish of the characin family (family Characidae) of order Characiformes. It is native to the Paraguay basin of southern Brazil. This species is of typical elongated tetra appearance; it is of plain basic coloration but with two distinct, adjacent longitudinal stripes, white above black. The eye has two thin but distinctive color bands across the top, red above yellow. It grows to a maximum overall length of approximately 4 cm (1.6 in). The fish's natural diet consists of small invertebrates and plants. Black neon tetras should be kept in soft acidic water, which should be kept clean at all times. Their tank should contain live plants, a darker substrate and open water for swimming. Black neons should be kept in groups of at least 4−6. The Black neon tetra requires the following aquarium conditions: pH 5 - 7 dH (hardness) 1 - 2 Temperature 20–26 °C (68–79 °F) These fish swim at the top level of the aquarium, and do not feed from the bottom of the tank. Therefore, it is recommended they be kept with bottom dwelling fish (such as pygmy corydoras) so that leftover food is then eaten up off the substrate and not left to waste. Black neon tetras can be fed a variety of foods, including flake, frozen and freeze dried food. Small live foods like worms and brine shrimp are also recommended as they bring out the fish's colours.