Taxonomy & naming
Hyphessobrycon haraldschultzi was described by H. Travassos in 1960, with the Araguaia River basin of Brazil as its provenance. The species has also appeared in the literature under the genus Megalamphodus, reflecting broader debates about generic limits within the Hyphessobrycon assemblage; modern sources including FishBase retain Megalamphodus haraldschultzi as an accepted synonym, though the Hyphessobrycon placement remains widely used in the hobby.
The genus Hyphessobrycon is one of the largest in the family Characidae, encompassing several hundred small to mid-sized tetras distributed across South and Central America. Its limits have long been contested: many species have been shuffled between Hyphessobrycon and allied genera such as Megalamphodus and Tetragonopterus, and ongoing molecular work continues to revise those boundaries. H. haraldschultzi sits within a cluster of small, reddish Hyphessobrycon species typical of central Brazilian drainage systems.
Morphology
Hyphessobrycon haraldschultzi is a very small fish, reaching approximately 1 in total length — FishBase records 1 in TL, while Seriously Fish gives a range of 1 in in aquarium specimens. The body is compressed and somewhat oval in profile, with the typical tetra shape: a moderately deep mid-body, forked caudal fin, and an adipose fin between the dorsal and caudal.
The colouration is translucent to pale reddish, with a delicate shimmer that accounts for the trade name Crystal Red Tetra. A darker mid-lateral stripe or shoulder spot may be present, as in many small Hyphessobrycon. Females tend to be slightly deeper-bodied and plumper when in condition, while males are slimmer; the difference is modest at this small size and most visible when a group contains ripe females.
Habitat
In the wild, Hyphessobrycon haraldschultzi is endemic to the rio Araguaia system of central and western Brazil. Seriously Fish records it from minor tributaries, backwaters, and oxbow lakes associated with this drainage — habitats characterised by slow or standing water, dense marginal and submerged vegetation, and accumulated leaf litter and organic debris.
Water conditions in these environments are soft and acidic: Seriously Fish notes pH 5–6 and temperatures around 75 °F; FishBase records a pH of approximately 7 and temperature of 72 °F, suggesting some variation across sites. The broad picture is a warm, soft, somewhat shaded microhabitat typical of lowland central Brazilian tributaries, where tannins from leaf litter and organic matter stain the water and keep mineral content low.
Feeding
Hyphessobrycon haraldschultzi is an omnivore. In the wild it takes small invertebrates and crustaceans, as well as filamentous algae and fallen fruit — a broad diet typical of a small characid exploiting the varied resources of backwater and floodplain habitats. FishBase categorises it as insectivorous, reflecting the predominance of invertebrate prey.
In the aquarium it readily accepts good-quality micro-pellets and fine flake food. Supplementing the diet with small live or frozen foods — micro-worms, baby brine shrimp, Daphnia, or Cyclops — improves condition and colour. Given its very small size, food particle dimensions matter: standard adult flake should be crushed fine, and live foods should be appropriately sized for a fish under 1 in.
Mating
Like the majority of small Hyphessobrycon, H. haraldschultzi is an egg-scattering free spawner. Males court females with fin displays and pursuit through fine-leaved vegetation or open water, driving the spawning act. There is no pair bond, and multiple males may participate in a single spawning episode when a group is kept together.
Spawning activity tends to peak in the morning, as is common in small tetras. Males in condition flush slightly more intensely and are noticeably slimmer than gravid females; conditioning the group on a varied diet with live foods helps bring both sexes into breeding readiness.
Breeding
Hyphessobrycon haraldschultzi spawns in the manner typical of small tetras: eggs are scattered adhesively among fine-leaved plants or spawning mops, and the adults provide no parental care. Left in the breeding tank, adults will consume both eggs and newly hatched fry, so breeders typically remove the spawning medium to a separate container or move the adults out after spawning is observed.
Eggs hatch within a few days at warm temperatures (around 75–79 °F). The fry are tiny at emergence and require very fine first foods — infusoria, rotifers, or commercial liquid fry food — before being large enough to take newly hatched brine shrimp nauplii. The water in the rearing vessel should be soft and slightly acidic, consistent with the species' natural preferences, and gentle filtration through a sponge filter is advisable to avoid drawing fry into the intake.
In the aquarium
The Crystal Red Tetra is best kept in a group of eight or more, which brings out schooling behaviour and reduces individual stress. A well-planted aquarium with subdued lighting, a dark substrate, and some tannin from driftwood or dried leaves replicates its Araguaia backwater origins and shows the fish at their most settled. Given its very small adult size, it is suitable even for nano aquaria of 10–15 US gal for a small group, though a longer tank allows more natural schooling behaviour.
Water chemistry should lean soft and acidic — pH 5.5–7.0 and temperatures of 72–79 °F suit it well. The species is peaceful and can be combined with other small tetras, rasboras, Corydoras of appropriate size, and dwarf cichlids that do not prey on fish under 1 in. It is not demanding once water quality is stable, but like many small Neotropical species it is sensitive to the sudden parameter swings that accompany poor maintenance or overstocking.
Conservation
Hyphessobrycon haraldschultzi was assessed as Least Concern (LC) on the IUCN Red List, with the assessment completed on 7 November 2018. The Araguaia basin supports a large and partly intact river system, and no specific range-wide threats have elevated the species above LC status at the time of assessment.
Nonetheless, the broader Araguaia drainage faces pressure from agriculture, deforestation, and associated sedimentation and water-quality changes that affect small-stream specialists. As with many small Neotropical tetras, range-restricted habitat degradation could affect local populations without triggering an immediate global reassessment. Aquarium specimens are primarily tank-bred, which reduces any collecting pressure on wild populations.