Taxonomy & naming
Hyphessobrycon cyanotaenia was described by Zarski and Géry in 2006. The species belongs to Hyphessobrycon, one of the largest and most species-rich genera in the family Characidae, encompassing hundreds of small tetras distributed across South and Central America. The valid name as governed by Eschmeyer's Catalog of Fishes is Hyphessobrycon cyanotaenia Zarski & Géry, 2006.
Morphologically, the original description notes diagnostic characters including 13–15 branched anal-fin rays and a scale formula of 5/(6–9) 27–30/3–4 — a relatively large-scale count for its body size. These meristic details place it within the broader Hyphessobrycon assemblage but distinguish it from the many closely related species in the genus. The species was collected from Brazil and entered the ornamental-fish trade around the time of its description, with wild-caught specimens noted from importers.
Morphology
Hyphessobrycon cyanotaenia is a small characid reaching approximately 1.5 in standard length, consistent with the general size range of hobbyist-targeted Hyphessobrycon. The body is laterally compressed and moderately deep, typical of the genus. The characteristic feature that earns the common name 'Lapis Tetra' is a vivid iridescent blue lateral stripe or band running along the body, which in good light and condition gleams with an intense lapis-blue sheen.
As with most Hyphessobrycon, the fins are relatively clear to lightly pigmented, and the overall impression is of a small, bright fish whose colour intensity varies with mood, lighting, and condition. Wild-caught specimens are often noted as particularly vibrant compared to tank-bred stock in some imports. Sexual dimorphism follows the genus pattern: females are typically fuller-bodied when gravid, while males may display more intense colouration.
Habitat
Hyphessobrycon cyanotaenia originates from Brazil. Precise locality data from the original description is limited in available sources, but the species inhabits freshwater environments typical of the Neotropical lowland fish fauna — vegetated areas in still or slow-moving water where fine-leaved aquatic plants and submerged structure provide cover.
Water conditions reported for the species are soft and acidic, consistent with the lowland Brazilian habitats where many small Hyphessobrycon are found: a pH around 5 and a temperature of approximately 79 °F are cited. In the wild, such habitats often correspond to blackwater or clearwater systems with low mineral content, dim light filtering through overhanging canopy, and a substrate of leaf litter or fine sand.
Feeding
Hyphessobrycon cyanotaenia is an omnivore, feeding on a variety of small food items in the wild. Like most small tetras in its genus, it likely takes small invertebrates — zooplankton, insect larvae, and micro-crustaceans — alongside algae and organic detritus in its natural vegetated habitat. It is described as diurnal in activity.
In the aquarium the species accepts prepared foods readily. A diet of small-grade flake or micro-pellets forms an adequate base, but condition and colour are best maintained with regular supplementation of frozen or live foods such as Daphnia, brine shrimp nauplii, and micro-worms. Given its small size, food particle size matters — very fine grades or crushed flake are appropriate, especially for smaller individuals.
Mating
Hyphessobrycon cyanotaenia is an egg-scattering open spawner, as is standard for the genus. Males court receptive females with displays in which fin posture and body colour are intensified. The species is described as shoaling and social, and keeping a group rather than a single pair typically elicits natural courtship behaviour, with males competing for female attention through display.
Spawning occurs among fine-leaved plants or similar structure, where the pair scatter adhesive eggs that attach to vegetation or substrate. No pair bond is formed and there is no parental care — both sexes will consume eggs given the opportunity, which shapes the practical approach to breeding.
Breeding
Breeding Hyphessobrycon cyanotaenia follows the standard Hyphessobrycon protocol. Conditioned adults are moved to a small, dimly lit breeding tank furnished with clumps of fine-leaved plants such as Java moss or synthetic spawning mops. Water should be soft and slightly acidic, around pH 5–6.5 and 79 °F, matching the species' natural conditions. A thin layer of substrate or a mesh covering the bottom protects eggs from being eaten.
The pair or small group scatter adhesive eggs among the plants. Because adults will readily consume the eggs, breeders remove the adults promptly after spawning, or harvest the spawning medium to a separate rearing vessel. Eggs hatch within a few days at breeding temperature, and the tiny fry initially require infusoria or commercial micro-fry food before graduating to newly hatched brine shrimp nauplii as they grow. No parental care is provided at any stage.
In the aquarium
The Lapis Tetra is suited to a planted nano or small community aquarium. It is noted as a shoaling species that does best in groups; a minimum of six individuals allows natural schooling behaviour and reduces individual stress. Its small size — under 1.5 in — makes it appropriate for tanks from around 23.5 in in length, provided water quality is stable. The species is described as diurnal and as hiding with larger tank-mates when kept in mixed company, so it is best paired with similarly sized, peaceful companions.
Water chemistry should reflect the soft, acidic conditions of its Brazilian origin: pH around 5 to 6.5, temperature approximately 77–81 °F, and low to moderate hardness. A well-planted tank with some surface cover, gentle filtration, and subdued or diffused lighting will encourage the fish to venture into open water and display its best colour. The species' vivid blue band is most striking under moderate lighting conditions where iridescence can develop fully. It is an active, peaceful shoaling fish with no particular difficulty in care, provided soft, acidic water is maintained.
Conservation
Hyphessobrycon cyanotaenia is assessed as Least Concern (LC) on the IUCN Red List, with the assessment dated 7 November 2018. This status reflects an absence of evidence for significant population decline or major threats across its Brazilian range at the time of assessment.
As a Brazilian freshwater species, it shares the general conservation context of small Neotropical fish: ongoing pressures from habitat loss through deforestation, agricultural runoff, and water-course modification in the Amazon basin and associated drainages affect many species in the region, even those not currently considered threatened. Wild-caught specimens have been imported into the ornamental trade. Sourcing captive-bred stock where available reduces pressure on wild populations, though the Least Concern status indicates the species is not currently considered at elevated risk.