Black neon tetra

Water parameters

Tolerated range for this species. Aim for the middle of each band rather than the extremes.

Tank and habitat

Substrate: any.

Behavior

Plant interaction: plant safe.

Feeding

An undemanding feeder. Flake food, micro pellets, frozen daphnia, frozen brine shrimp, and frozen bloodworm are all accepted without fuss. The mouth is small for a tetra of this size, so crushing larger flake pieces or picking a finer brand keeps food reachable. The fish feeds in midwater and mostly ignores food that has reached the substrate. Two small feedings a day works better than one large one. The natural diet runs to small worms, crustaceans, and plant matter. Conditioning a pair for spawning is done with frozen food twice daily for a week or so beforehand.

Compatibility

• Among the more tolerant of the small tetras when it comes to water chemistry. Wider hardness range than neon or cardinal tetras, often kept successfully in moderately hard tap water without an RO system
• Belongs to a different genus than the neon tetra (Hyphessobrycon vs Paracheirodon), despite the name. The two are visually similar but not directly related
• Schools well with other peaceful tetras, rasboras, and small catfish. The black-and-gold flank contrast looks its best in a confident group of six or more (ten or more if there is room), against a darker background
• Useful as a dither fish for shy bottom species; an active midwater school of these signals safety to fish that otherwise spend the day hiding

Origin and habitat

A small characin from the upper rio Paraguai basin in southern Brazil, ranging through Mato Grosso and Mato Grosso do Sul states both north and south of the Pantanal wetlands. The type locality is Coxim, on the upper Taquari, with collection records also from the upper Sepotuba near Tangara da Serra; the species is presumed to occur through drainages between those two. A feral population has established in the rio Paraiba do Sul in southeastern Brazil after escapes from the ornamental trade. The species was described by Geryin 1961 in Tropical Fish Hobbyist magazine and named after Herbert R. Axelrod (1927 to 2017), the magazine's publisher, who produced a large body of aquarium literature in the mid-20th century. Despite the common name and visual resemblance, this is not closely related to the neon tetra; the two sit in different genera (Hyphessobrycon vs Paracheirodon) within the family Acestrorhamphidae, an American-characin family in the order Characiformes (some sources still place the species in the older family Characidae). The body has the typical narrow tetra outline, decorated with two adjacent longitudinal stripes (white above black) along the sides, and the eye has two thin colour bands across the top, red over yellow. A selectively bred 'Diamond' or 'Brilliant' form has no white stripe, replaced by reflective scales near the head. Females grow slightly larger than males and are noticeably rounder when carrying eggs. The species reaches a maximum standard length of about 3.2 cm and roughly 4 cm total length. Wild fish live in small tributaries, creeks, flooded forest, and sand-bottomed margins of slow water, mostly soft and tannin-stained. IUCN Least Concern. Captive-bred stock makes up almost all of the aquarium trade today, with an albino form available as well.

Breeding

An egg scatterer and easier to breed in home aquariums than the neon tetra. Condition a chosen pair on high-quality frozen food for a week to ten days. The breeding tank should be small (around 20 to 40 L), dimly lit, and either heavily planted with fine-leaved species or fitted with a spawning mop on the bottom. Water for spawning needs to be soft and acidic: pH 5.5 to 6.5 and GH around 4 or lower. Temperature near the top of the range (around 26 to 27 C) is the usual trigger, and spawning generally happens in the early morning. Males show more intensely contrasting stripes during display, and females are visibly fuller. The adhesive eggs scatter into the plants. Adults eat their own eggs, so the parents come out as soon as spawning ends. The eggs are also light-sensitive and develop better in a covered or dim tank. Hatching takes around 24 to 30 hours at typical aquarium temperature. Fry are very small and need infusoria or a commercial liquid fry food for the first few days before they can take baby brine shrimp. Growth is steady but not fast; juveniles reach saleable size in about three months.

Common problems

Hardy by tetra standards. In a stable, well-cycled tank with consistent water changes, disease is uncommon. The more frequent issue is behavioural: a group of fewer than about six fish stays nervous, hides behind plants, and shows pale, washed-out colour. The stripe contrast that makes the species worth keeping really only appears in a confident, properly-sized school of six or more (ten or more if the tank can hold them). Ich shows up sometimes in newly bought fish that have been stressed in transit, and responds to a standard heat and salt or commercial treatment. Fin rot can appear when water quality slips and is treated by addressing the conditions first. Otherwise, the species is one of the more forgiving small tetras in the trade.

Bioload

Further reading

• The schooling number matters more than you think