Taxonomy & naming
Holopristis haraldi was described by the French-Swiss ichthyologist Jacques Géry in 1961. The species has had a complicated nomenclatural career: it was at one stage treated as a subspecies, Hemigrammus pulcher haraldi, suggesting a close relationship with the pretty tetra H. pulcher, before being elevated back to full species rank. The Catalog of Fishes now places it in the genus Holopristis, making Holopristis haraldi the currently accepted valid name, with Holopristis haraldi as a senior synonym.
The family assignment remains Characidae. FishBase carries the species under Holopristis haraldi, and ITIS records the nomenclatural history under the original Holopristis haraldi Géry, 1961 combination. Because the valid name has moved to Holopristis, the authority is written without parentheses only when the original combination is cited; when using the current binomial Holopristis haraldi the authority parenthetical form applies.
This fish was long listed as Hemigrammus haraldi; Eschmeyer's Catalog of Fishes places the species in Holopristis, and the current combination Holopristis haraldi is followed here.
Morphology
Holopristis haraldi is a small, slender tetra with a maximum recorded standard length of 1.1 in. Like other members of the Hemigrammus-alliance tetras, it is laterally compressed with a typical characid body plan: a complete lateral line, two dorsal-fin elements (the first a single spine or hardened ray, the second a soft-rayed dorsal), a small adipose fin, and a forked caudal fin.
Detailed meristic and colour descriptions are sparse in the hobbyist literature. As a member of the Hemigrammus pulcher group it may share elements of that species' pattern — a dark humeral blotch and caudal marking — but field data for haraldi specifically are limited. Collectors and researchers working in the Purus and Negro drainages would be the best source of live-colour notes.
Habitat
The species is distributed across several major tributary systems of the upper Amazon River basin: records exist from the Purus, Tefé, Ucayali, Japurá, Negro, and Amazonas main-channel tributaries (FishBase). This broad distribution across large, ecologically diverse Amazonian drainages suggests it tolerates a range of water conditions, though it is fundamentally a tropical freshwater fish of the benthopelagic zone.
Amazonian white-water, black-water, and clear-water river systems each differ markedly in pH, conductivity, and sediment load, and a species recorded across the Purus (white-water), Negro (black-water), and Ucayali (Andean foothills) likely has some flexibility. Biogeographical work on Amazon fishes (Lowe-McConnell and colleagues) places small tetras like this one in the category of widespread Amazonian tributary fauna, associated with flooded forest margins and slow-flowing backwaters with abundant fine-leaved and floating vegetation.
Feeding
No specific dietary studies are available for Holopristis haraldi. Small Amazonian tetras in the Hemigrammus alliance are generally micropredatory omnivores, feeding on small invertebrates — zooplankton, small insect larvae, aquatic crustaceans — together with algae, diatoms, and organic detritus encountered while foraging in the water column and near the substrate.
In the aquarium, similarly sized tetras do well on high-quality micro-granules and small flake supplemented with frozen or live Daphnia, micro-worm, and newly hatched brine shrimp. A varied diet supports condition and colour in small characids generally.
Mating
No published account of mating behaviour in Holopristis haraldi is available. By analogy with closely related Hemigrammus and Holopristis species, the reproductive strategy is almost certainly open egg-scattering with no parental care. Spawning in small Amazonian tetras of this group typically involves brief courtship chases in which a male drives a receptive female into fine-leaved vegetation or among surface root mats, where eggs are scattered and left to their own fate.
Adhesive or semi-adhesive eggs sink into or cling to plant matter, and the adults take no further interest, commonly consuming any eggs within reach. Seasonal cues in the wild are likely tied to the Amazonian flood cycle, with peak reproductive activity associated with rising waters that flood marginal vegetation and provide both shelter and food for larvae.
Breeding
Holopristis haraldi has not been established in the hobby as a bred species, and no captive-breeding accounts appear in the accessible literature. Based on the biology of congeners and the genus Holopristis, the expected breeding mode is egg-scattering over fine-leaved plants or spawning mops, with adhesive eggs and no parental investment.
Anyone attempting to breed the species would likely follow the standard small-tetra protocol: a soft, slightly acidic, warm conditioning tank; a conditioning period on live and frozen foods; and separation of the adults from eggs and fry immediately after spawning. First foods for the tiny fry would be infusoria and rotifers before graduating to newly hatched brine shrimp nauplii. Data on clutch size, incubation time, and fry growth rate are absent from the published record.
In the aquarium
Holopristis haraldi is essentially absent from the international aquarium trade under any name and is not commercially bred. A fish of 1.1 in SL is well within the size range that small-tetra keepers favour, and any specimens that appeared in trade would suit the standard small-tetra setup: a planted, soft-to-moderately-hard tropical aquarium with gentle filtration and a group of six or more conspecifics to bring out natural schooling behaviour.
Because its current valid name is Holopristis haraldi rather than a Hemigrammus, catalogue and availability listings may vary. Aquarists seeking this species would need to cross-reference both names. In all practical respects the care requirements are those of any small Amazonian tetra: stable warm water (75–82 °F), subdued lighting with floating plants to reduce stress, fine-mouthed tankmates, and regular small feedings of varied foods.
Conservation
Holopristis haraldi (as Holopristis haraldi) was assessed by the IUCN Red List in November 2018 and placed in the Least Concern category. The assessment reflects the species' broad distribution across multiple large Amazonian river systems — Purus, Tefé, Ucayali, Japurá, Negro, and Amazonas — which collectively represent a large extent of occurrence with no evidence of rapid population decline.
The upper Amazon basin faces ongoing pressure from deforestation, agricultural run-off, artisanal gold mining, and dam construction in some tributary systems. For a broadly distributed small tetra these threats are unlikely to constitute a range-wide crisis in the near term, which supports the Least Concern listing. Population-level data for this specific taxon are sparse, and a future assessment with improved occurrence data would give a clearer picture of any trends.