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 (1.5 in). Despite its common name, it does not particularly resemble the neon tetra, which belongs to a different genus.The fish's natural diet consists of small invertebrates and plants.H. herbertaxelrodi is commonly kept as an aquarium fish by hobbyists.The black neon tetra is sometimes called the black tetra, but that name more properly refers to a different species, Gymnocorymbus ternetzi.
In the aquarium
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 - 80°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.
Black neon tetras can be spawned rather easily if the water quality is right. Before attempting to breed the black neon tetra, condition the prospective parents with good food. Fish of about one year old are suitable for breeding. The sex of the fish can be determined by its body shape, the female being much deeper in the body than the male.Although the black neon tetra can be kept in water harder and more alkaline than its natural habitat, for breeding it is necessary to get closer to what it would get in the Amazon. Breeding the black neon tetra requires acidic water with no more than four degrees of hardness. Use dim lighting.The black neon tetra is an egg scatterer, laying adhesive (sticky) eggs over plants, etc. One female can produce several hundred eggs. The parents will eat their own eggs and babies, so it is normal to remove the parents after spawning. As with many fish, The black neon tetra often spawns in the early morning. Raising the fry can be more difficult because of their small size. The first food will normally be protozoa (infusoria). Very fine fry food can be used, graduating to slightly coarse fry food. At all ages, The black neon tetra benefits from suitably sized live food.Breeding of the black neon tetra is mentioned on this websites: http://www.bettatrading.com.au/Black-Neon-Tetra-Fact-sheet.php