Black neon tetra

The black neon tetra (Hyphessobrycon herbertaxelrodi) is a freshwater fish of the characin family (Characidae) of the order Characiformes. It is native to the Paraguay basin of southern Brazil. They are often found in the aquarium trade.

Taxonomy
The species is named in honor of pet-book publisher Herbert R. Axelrod (1927–2017), whose Tropical Fish Hobbyist magazine published this description and several others by Géry.

Description
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. Befitting its common name, it slightly resembles the neon tetra, which belongs to a different genus (Paracheirodon)

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 are kept in soft acidic water. Aquarists recommend that the water be kept clean at all times; that the tank contain live plants, a darker substrate and open water for swimming; and that the fish be kept in groups of at least 6, preferably more. The recommended minimum aquarium volume for a group of 6 is about 15 US gallons (60 L), and for a group of 8–10 fish, about 20 gallons.

Because black neon tetras swim at the top level of the aquarium, and do not feed from the bottom of the tank, aquarists keep them 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 are fed a variety of foods, including flake, frozen and freeze dried food. Small live foods like worms and brine shrimp are said to bring out the fish's colors.

Breeding
Black neon tetras can be spawned rather easily if the water quality is right. Before attempting to breed the black neon tetra, breeders condition the prospective parents with live food. Fish around one year old can be suitable for breeding. The sex of the fish is determined by its body shape, the female being much rounder and more plump than the males. Although the black neon tetra can be kept in water harder and more alkaline than its natural habitat, for breeding it is necessary to be closer to what it would feel like in the Amazon. Breeding the Black neon tetra requires acidic water with no more than four degrees of hardness.

The black neon tetra is an egg scatterer, laying adhesive (sticky) eggs over plants, etc. One female can produce several hundred eggs. The parents eat their own eggs, so the parents are normally removed 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), then Daphnia. Usually very fine fry food is used, graduating to slightly coarse fry food. At all ages, the black neon tetra benefits from suitably sized live food.