Taxonomy & naming
Roeboexodon geryi was described by the American ichthyologist George S. Myers in 1960. The species is the only member of its genus, making Roeboexodon a monotypic taxon within the family Characidae. Eschmeyer's Catalog of Fishes (Catalog of Fishes, CAS) is the governing authority for the valid name.
The generic epithet Roeboexodon combines elements referencing the fish's affinity and dental or structural characters, in keeping with the naming conventions common for small Amazonian characids of the mid-twentieth century. The specific epithet geryi honours the French ichthyologist Jacques Géry (1917–2007), whose prolific work on Neotropical characids made him one of the foremost authorities on the group; patronyms for Géry appear across numerous small tetra genera described during the same era.
Morphology
Roeboexodon geryi is a small characid. FishBase records a maximum total length in the vicinity of 6 in, though in practice most individuals encountered are considerably smaller, and the figure may reflect an outlier or a conversion artefact — data for this species in the primary literature are sparse.
Like many small Amazonian characids it is a slender, laterally compressed fish with the family's characteristic adipose fin and a terminal mouth. Beyond these general features, detailed morphological descriptions are not widely available in accessible sources; the original 1960 description by Myers remains the principal reference for diagnostic characters.
Habitat
Roeboexodon geryi is recorded from the Amazon basin. Beyond this broad attribution, fine-scale habitat data — specific river systems, water-body types, vegetation associations, or substrate preferences — are not documented in the sources consulted for this profile.
Amazonian characids of similar size and body form typically inhabit the shallow margins of streams, floodplain lakes, and flooded forest (igapó or várzea), where warm, soft, acidic black- or clearwater is common. Whether Roeboexodon geryi is specifically associated with such conditions has not been confirmed by published field data available to this account.
Feeding
No specific feeding data for Roeboexodon geryi appear in the sources reviewed. Small Amazonian characids of similar form are generally opportunistic omnivores, taking small invertebrates, zooplankton, insect larvae, and plant material in proportion to local availability.
In the aquarium, related small tetras accept a broad diet of good-quality micro-pellets, flake, and small frozen foods such as Daphnia, brine shrimp, and Cyclops. These remain reasonable starting points for any husbandry attempt with Roeboexodon geryi, though the species is not established in the trade and practical feeding observations are absent from the literature consulted.
Mating
Reproductive behaviour has not been documented for Roeboexodon geryi in the sources available for this profile. The species is monotypic in its genus and has not been the subject of detailed ethological study.
By analogy with the broader Amazonian characid fauna, open egg-scattering spawning over fine-leaved vegetation or leaf litter, with no parental care, is the likely reproductive strategy. Males of many small tetras develop minor morphological differences from females during breeding condition, but whether such differences occur in Roeboexodon geryi is unrecorded.
Breeding
Roeboexodon geryi is not established in the ornamental fish trade and has not been bred in captivity under documented conditions known to the sources consulted for this profile. No clutch-size, incubation-period, or fry-rearing data are available.
Until the species becomes better represented in collections and the literature, practical breeding guidance cannot be given beyond the general characid framework: soft, slightly acidic warm water, fine-leaved plants or spawning mops, separation of adults from eggs after spawning, and small live or liquid first foods for fry. These represent hypotheses to test rather than confirmed protocol.
In the aquarium
Roeboexodon geryi is rarely if ever available in the ornamental fish trade and should be considered a specialist or collector's fish at best. Seriously Fish lists a care profile for the species, which is the most accessible hobbyist reference; beyond that, practical aquarium notes are sparse.
If kept, the general principles applicable to small Amazonian tetras are a reasonable starting framework: a well-planted aquarium with soft, acidic, warm water (around 75–82 °F), low light, peat or leaf-litter conditioning, and peaceful tankmates of similar size. The species has no established common name in English, reflecting its rarity in hobby contexts.
Conservation
Roeboexodon geryi has not been assessed by the IUCN Red List; its conservation status is Not Evaluated (NE). No specific threat assessments, population estimates, or range-wide surveys have been published in the sources reviewed for this profile.
As an Amazonian species the broad threats facing the region — deforestation, agricultural and mining pollution, and hydrological alteration — may apply, but without a formal assessment or range data the conservation situation of Roeboexodon geryi specifically cannot be characterised. The species' rarity in collections and literature may itself reflect genuinely low abundance in the wild, or may simply reflect collector and research effort directed elsewhere.