Taxonomy & naming
Parastremma pulchrum was described by Georg Dahl in 1960. The genus Parastremma was established by Carl H. Eigenmann in 1912; it is placed within the family Characidae, though historical sources have also associated it with a broader characid classification framework. Catalog of Fishes records the valid name as Parastremma pulchrum Dahl, 1960.
The genus name Parastremma is of Greek derivation, combining para- (beside, near) with stremma (a turning or twist), alluding to morphological features noted by Eigenmann in his original genus diagnosis. The species epithet pulchrum is Latin for beautiful or handsome, a common epithetical nod to the appearance of a newly described fish. Only a handful of species are assigned to Parastremma, and detailed revisionary work on the genus remains limited.
Morphology
Parastremma pulchrum is recorded at a maximum size of 4 in standard length, placing it in the mid-sized range for a characin. Like most members of the family it is a laterally compressed, streamlined fish with a forked tail and the small adipose fin characteristic of characids.
Detailed morphological data for this species are sparse in the accessible literature. FishBase classifies it as benthopelagic, suggesting it occupies both the lower water column and mid-water zones. The specific epithet pulchrum (beautiful) implies the original description found its colouration or proportions noteworthy, but published illustrations or detailed colour descriptions are not widely available for this species.
Habitat
Parastremma pulchrum is endemic to the Atrato River basin on the Atlantic versant of Colombia. The Atrato is one of Colombia's major lowland rivers, draining the Chocó biogeographic region — one of the world's most biodiverse areas — and flowing north into the Gulf of Urabá. Related hobbyist records also reference the San Juan basin, a Pacific-versant system that shares the Chocó lowlands and whose river corridors include submerged wood, overhanging riparian vegetation, and tannin-stained or moderately turbid waters typical of Neotropical lowland rivers.
The Chocó lowlands experience extremely high annual rainfall, resulting in rivers that are typically warm, soft, and slightly acidic to neutral in chemistry. Precise water-parameter records for Parastremma pulchrum collection sites are not available in the accessible literature, but conditions consistent with the broader Atrato basin — temperatures in the mid-to-upper 20s Celsius, low to moderate conductivity, and pH near neutral — are reasonable working parameters.
Feeding
No detailed dietary studies of Parastremma pulchrum are available in the literature. Like most characins of similar body form and habitat, it is presumed to be an opportunistic omnivore, feeding on small invertebrates, insect larvae, and organic material available in the water column and at substrate level in its lowland river habitat.
In an aquarium context, similar-sized Neotropical characins of the Chocó region accept good-quality flake and micro-pellet foods alongside frozen and live foods such as Daphnia, brine shrimp, and bloodworm. A varied diet is advisable to maintain condition in any Parastremma held in captivity, though the species is rarely encountered in the hobby.
Mating
No specific mating observations for Parastremma pulchrum have been published. The genus belongs to a large lineage of characins that characteristically spawn by scattering adhesive or semi-adhesive eggs among fine-leaved aquatic plants or over substrate, with no parental care from either sex after spawning.
Displays between males in such species typically involve lateral posturing and fin-spreading. Spawning is usually triggered by conditioning on live and frozen foods combined with a slight rise in temperature or a water change simulating seasonal cues, as is standard for open-water characin spawners.
Breeding
Breeding records for Parastremma pulchrum in captivity are not documented in the available literature. By analogy with other similarly sized Neotropical characins, the species would be expected to be an egg-scattering open spawner, depositing small adhesive eggs among fine-leaved vegetation or spawning mops, with no parental care.
Adults of egg-scattering characins will consume their own eggs, so in a managed breeding setup the eggs or spawning medium should be removed promptly after spawning. Fry typically require infusoria or other very fine first foods initially, progressing to newly hatched brine shrimp as they grow. Because this species is essentially unknown in the hobby, no first-hand captive breeding reports are available.
In the aquarium
Parastremma pulchrum is not an established hobby fish and is unlikely to be encountered in the retail trade. The Atrato and San Juan river basins of Colombia do yield a range of characins and other fish that occasionally enter specialist channels, but this species specifically has no documented history of captive husbandry.
For aquarists who do obtain specimens — most likely as part of a scientific or specialist biotope collection — conditions matching the Chocó lowland river environment would apply: warm, soft to moderately hard, slightly acidic to neutral water; a well-filtered tank with gentle current and some cover of submerged wood or fine-leaved plants; and a peaceful community of similarly sized fish. The species' benthopelagic designation suggests it would use the mid and lower water column. Data are too sparse to assign a care rating with confidence.
Conservation
Parastremma pulchrum is assessed as Data Deficient (DD) on the IUCN Red List, with the most recent assessment dating to 2022. The Data Deficient designation indicates that insufficient information is available to make a direct or indirect assessment of its extinction risk — the species has not been the subject of enough targeted survey work to determine population size, trend, or the extent to which its habitat is threatened.
The Atrato River basin lies within the Chocó biogeographic province, a region under sustained pressure from deforestation, gold mining, and agricultural expansion. While these threats affect many aquatic species in the region, whether and to what degree they affect Parastremma pulchrum specifically remains unknown. The Data Deficient assessment is best understood as a flag for needed survey work rather than an indicator of safety; a narrowly endemic fish in a heavily impacted river system warrants closer attention.