Taxonomy & naming
Hyphessobrycon margitae was described by Axel Zarski in 2016 from specimens collected in the río Nanay drainage of Peru. The description was published in the journal Vertebrate Zoology. The species belongs to the large and species-rich genus Hyphessobrycon within the family Characidae, a genus that encompasses a substantial portion of the small characins commonly called tetras in the aquarium hobby.
Before the formal description was published, the species circulated in the hobby under vernacular names — most widely as the Red-Blue Peru or Bleeding Blue Tetra — reflecting both its origin and its bold colour pattern. Those pre-description trade names are among the better-documented for any new tetra and indicate the fish was in circulation with hobbyists before its formal scientific recognition. The valid name, per Eschmeyer's Catalog of Fishes, is Hyphessobrycon margitae Zarski, 2016.
Morphology
Hyphessobrycon margitae is a small tetra reaching approximately 1.5 in standard length. The body plan is the typical slender-to-moderately-deep Hyphessobrycon shape — laterally compressed, with a blunt snout and the adipose fin present as in all members of the genus.
The species' signature is its coloration: the body combines red and blue tones in a pattern that is vivid by any tetra standard. The precise arrangement — a reddish body ground with blue or iridescent blue-violet zones — contributes to the common names coined by hobbyists before the species had a scientific name. Colour intensity, as in most tetras of this group, varies with condition, lighting, and mood; well-settled, well-fed individuals in a mature tank are the most striking. Females are typically plainer and rounder-bodied than males, following the general dimorphism of the genus.
Habitat
Hyphessobrycon margitae originates from the río Nanay drainage in Peru, a blackwater tributary system that feeds into the upper Amazon near Iquitos. The Nanay is characteristic Amazonian blackwater: low pH, very soft, tannin-stained water with minimal dissolved minerals. Temperatures in such environments typically fall in the tropical range of the low-to-mid 20s Celsius.
FishBase records the species as benthopelagic and freshwater, indicating an association with the lower and mid water column in its natural habitat. Like most Hyphessobrycon species, it presumably inhabits sheltered areas of slow-moving or still water near marginal vegetation, submerged roots, and leaf litter — the structural complexity typical of blackwater streams and flooded forest in the upper Amazon basin.
Feeding
In the wild, Hyphessobrycon margitae is presumed to feed as an opportunistic omnivore in the manner typical of small Hyphessobrycon tetras: small invertebrates including microcrustaceans, insect larvae, and worms, supplemented with fine organic material and algae. The specific diet has not been studied in detail, but the gut morphology and ecology of the genus are well established.
In the aquarium, the species accepts a wide range of prepared and live foods. Small flake and micro-pellets form a convenient staple; regular additions of small live or frozen foods — Daphnia, baby brine shrimp, micro-worms, Cyclops — improve colour, condition, and spawning readiness. As with most small tetras, a varied diet yields noticeably better results than flake alone.
Mating
Hyphessobrycon margitae is an egg-scattering open spawner in the manner common to the genus, with no parental care. Males display toward females and rival males with intensified colour and spread fins. Courtship drives are typically brief, with a receptive female moving alongside or beneath the male as the pair weave through fine-leaved vegetation.
As with most small characins, spawning is not tied to a fixed season in the aquarium but can be triggered by suitable conditioning — a period of varied feeding, a slight temperature rise, and the addition of soft, slightly acidic water can all stimulate readiness. The presence of fine-leaved plants or spawning mops gives the pair a substrate to scatter eggs into.
Breeding
Breeding Hyphessobrycon margitae follows the standard small-tetra protocol. A conditioned pair or small group is moved to a shallow breeding tank furnished with fine-leaved plants (Java moss, hornwort) or synthetic spawning mops and filled with soft, slightly acidic water at around 75–79 °F. Eggs are small, adhesive, and scattered among the plants or mops.
Because the adults show no parental instinct and will readily consume eggs and fry, the spawning medium should be removed or the adults separated immediately after spawning is complete. Eggs hatch within roughly 24 to 48 hours at typical breeding temperatures; the fry become free-swimming a few days later and require very small first foods — infusoria, rotifers, or a commercial liquid fry food — before graduating to newly hatched brine shrimp nauplii as they grow. Soft, clean water and small regular water changes support fry development.
In the aquarium
Hyphessobrycon margitae is an adaptable species that acclimates well to a range of water conditions once settled, though it is at its best — and most colourful — in soft, slightly acidic water that mirrors its blackwater origins. A pH of 6.0–7.0 and temperatures of 75–79 °F are appropriate targets; the species has been noted to tolerate a wider range than that in practice.
Being a small, peaceful schooling fish, it should be kept in groups of six or more. A planted tank with dim or moderate lighting, some surface cover, and soft filtration shows the colours well and keeps the fish relaxed and active. Tankmates should be similarly sized and non-aggressive — other small tetras, dwarf corydoras, apistogrammas, and small rasboras are all compatible choices. The species remains underrated in the hobby relative to its visual appeal; well-maintained groups display a level of colour that rivals far more expensive fish.
Conservation
Hyphessobrycon margitae has not been assessed by the IUCN Red List and carries no formal conservation status. The species is recorded from the río Nanay drainage in Peru, a watershed that remains relatively intact compared with more heavily deforested parts of the Amazon basin, though it faces the general pressures of deforestation, land conversion, and river modification that affect the broader region.
The species was described only in 2016, and survey data sufficient for an IUCN assessment have not been compiled. Its presence in the aquarium hobby as a tank-bred species reduces demand for wild-caught individuals, which is a modest but positive factor. As with most recently described small Amazonian tetras, the extent of its natural range and population status remain poorly known.