Taxonomy & naming
Hemigrammus rubrostriatus was formally described by Axel Zarske in 2015 in the journal Vertebrate Zoology (volume 65, issue 1, pages 3–14), in a paper that simultaneously revalidated the related Hemigrammus falsus Meinken, 1958. The type material traced back to a commercial importation by Aquarium Glaser in 2013, originating from Colombia, and that import event is closely associated with the type locality. Eschmeyer's Catalog of Fishes (Catalog of Fishes, CAS) treats the valid name as Hemigrammus rubrostriatus Zarske, 2015.
Zarske placed the species in the H. ocellifer species-group on the basis of a suite of shared characters, including a vertically elongated humeral spot and the shape of the caudal spot. The WorldFish Wiki records the distribution as straddling the Colombia–Venezuela border area of the Orinoco basin, which partially overlaps with the Colombian assignment recorded in FishBase; the precise type locality has not been publicly mapped in detail. The genus Hemigrammus is one of the largest in the family Characidae, encompassing dozens of small to mid-sized tetras distributed across tropical South America, and the group shows considerable convergence in body pattern, making careful meristic study essential for species delimitation.
Morphology
Hemigrammus rubrostriatus is a slender, moderately compressed tetra that reaches a maximum of approximately 2 in standard length (SL) according to FishBase, with hobbyist reports generally giving 1.5–2 in at maturity. The body depth sits at roughly 2.91 times standard length and the head length at about 3.99 times SL — proportions typical of the elongated end of the Hemigrammus range. Scale counts run to 34–36 scales in the longitudinal series, with 10–15 pored scales on the lateral line. The anal fin carries iii–iv spines and 19–21 soft rays.
The colour pattern is the defining feature. A sharp, vertically elongated humeral spot sits just behind the operculum. Most conspicuous is the broad vermilion longitudinal band that originates at the operculum and runs straight to the base of the caudal fin, where it terminates in an asymmetric, elongated caudal spot. This red stripe is the basis for the specific epithet. In life, on well-conditioned fish, the band is intense enough to distinguish the species at a glance from related tetras that carry only a pale or yellowish lateral stripe.
Habitat
The species originates from the northern Amazon and Orinoco drainage systems of Colombia and the adjacent Colombia–Venezuela border region. Fishipedia notes habitat as low-flow rivers and wetlands characterised by clear, amber-tinted water with low mineral content — the blackwater or clearwater conditions typical of many Amazonian and Guianan tetra habitats, where tannins from leaf litter stain the water and conductivity is minimal.
Reported water parameters for these habitats are soft and acidic: temperatures in the range of 75–82 °F and pH values of 6.0–6.5. These are conditions broadly shared by many Colombian tetras associated with igapó-type forest streams and low-gradient floodplain channels, where fluctuating water levels and dense riparian vegetation create the fine-grained, dimly lit microhabitats that characids colonise year-round.
Feeding
Fishipedia characterises Hemigrammus rubrostriatus as a carnivore in the wild, taking micro-prey including small worms and microcrustaceans, which is consistent with the feeding ecology of most small Hemigrammus species that forage in the water column and at the surface film.
In the aquarium the species accepts standard small-tetra foods readily. A diet combining quality micro-pellets or fine flake with regular offerings of live or frozen foods — Artemia nauplii, Daphnia, small bloodworm, Cyclops — will maintain condition and help preserve the vibrancy of the red stripe. Feeding variety is worth the effort given that the lateral band is the fish's primary aesthetic feature and fades somewhat under nutritional stress.
Mating
Like all Hemigrammus species, H. rubrostriatus is an egg-scattering open spawner with no parental care. Courtship involves the male pursuing and nudging the female, displaying the lateral stripe at full intensity as a signal of condition and vigour. Spawning takes place in or near fine-leaved vegetation or among leaf litter, with adhesive eggs deposited among plant stems or on submerged surfaces.
No published detailed behavioural account of this species exists in the primary literature, but the pattern is consistent with that of closely related species in the H. ocellifer group: pair or group spawning in which eggs scatter widely, offering no post-spawn cohesion that would facilitate parental attendance. Males are likely to display most intensely when multiple individuals are present, and the red stripe probably functions as a visual signal during intraspecific competition as well as courtship.
Breeding
Fishipedia records the species as oviparous, spawning in open water among vegetation or leaf litter — the standard Hemigrammus pattern. Breeding protocol in captivity follows the general small-tetra approach: a species tank or dedicated breeding vessel with very soft, slightly acidic, warm water (around 79–82 °F, pH 6.0–6.5, low conductivity), furnished with fine-leaved plants such as Java moss or synthetic spawning mops. A pair or small group can be conditioned on live and frozen foods before being moved to the breeding setup.
Eggs are adhesive and small; the adults should be removed after spawning as they will readily eat the eggs. At tropical temperatures eggs typically hatch within 24–36 hours, and the fry are free-swimming a few days later. First foods are infusoria, rotifers, or commercial liquid fry food, progressing to freshly hatched brine shrimp nauplii as the fry grow. Data on clutch size and incubation time specific to this species are sparse in published sources.
In the aquarium
Hemigrammus rubrostriatus first appeared in the European aquarium trade through Aquarium Glaser in 2013, before its formal description, and it has since established a modest following among tetra enthusiasts drawn to the vivid red stripe. Amazonas Magazine noted that at roughly 2 in it falls outside the nano tank bracket and is best suited to a standard small community or species tank of 15 US gal or more.
Soft, acidic, well-filtered water replicating its Colombian blackwater origins suits the species best: pH 6.0–6.5, conductivity low, temperature 75–82 °F. Dense planting with open swimming lanes and subdued or dappled lighting shows the red stripe to greatest effect; bright hard light over a sparse tank tends to wash out the colour and makes the fish skittish. Keep in groups of six or more — like most tetras it is more settled and better coloured in a school. Compatible with other peaceful, small blackwater fish: pencilfish, dwarf cichlids such as Apistogramma, and other soft-water tetras all work well as tankmates.
Conservation
Hemigrammus rubrostriatus is listed as Data Deficient (DD) on the IUCN Red List, a status that reflects how recently the species was formally described and how little population-level field data exist rather than any confirmed assessment of abundance or threat. The DD designation means neither that the species is secure nor that it is threatened — it means the information required to make that determination is lacking.
The species is associated with Colombia's river systems, which face ongoing pressures from deforestation, agricultural run-off, and artisanal gold mining that degrades water quality and alters the fine-grained blackwater habitats on which many endemic characids depend. Because it entered the trade as a wild-caught import before its scientific description, any future population surveys will need to account for its commercial collection history. Aquarists keeping the species may want to seek tank-bred stock where available, as wild populations remain poorly monitored.