Taxonomy & naming
Inpaichthys parauapiranga was formally described in 2024 by Ferreira, Ribeiro, Lima, Silva, Ferreira, and Mirande, with the original description published in Neotropical Ichthyology (volume 22, issue 1, e230113). The type locality is a tributary of the rio Canamã, within the rio Aripuanã drainage of Mato Grosso state, Brazil; the holotype is CPUFMT 7908, a specimen of 1 in standard length. Eschmeyer's Catalog of Fishes (CAS) governs the valid name.
The genus Inpaichthys was erected for the well-known royal tetra (I. kerri), and the addition of I. parauapiranga marks only the second species assigned to the genus. Inpaichthys is placed within Characidae in the broad sense, and its relationships to other small softwater characids of the central and southern Amazon basin remain an active subject of systematic study. The specific epithet parauapiranga refers to the Parauapebas River Basin region of Pará, reflecting the broader geographic context of the species' discovery and trade distribution.
Morphology
Inpaichthys parauapiranga is a small tetra, reaching approximately 1 in standard length based on survey data recorded in FishBase, while trade specimens are noted at 1.5–2 inches (roughly 1.5–2 in) total length, suggesting some growth beyond the holotype size. The body shape is typical of small characids: laterally compressed, moderately deep, with the streamlined profile suited to life in slow forest streams.
The common name Scratched Inpa Tetra refers to markings on the body that distinguish the species from I. kerri. Males show a dark margin along the anal fin, a sexually dimorphic character noted in the original description. As with other small characids, overall coloration includes metallic lateral elements and dark patterning whose precise expression depends on lighting conditions, health, and reproductive state. Detailed meristic and morphometric data are available in the original Neotropical Ichthyology description.
Habitat
The type locality is a narrow, shallow stream — a tributary of the rio Canamã in the rio Aripuanã basin — with clear water, a sandy bottom, and aquatic vegetation. Water conditions at the collection site were recorded as 79 °F and pH 6.5, consistent with the soft, warm, slightly acidic blackwater and clearwater streams typical of central Amazonian lowland forest.
Hobbyist sources associate the species more broadly with the Parauapebas River Basin in the state of Pará, describing clear, slow-moving forest streams with leaf litter and overhanging vegetation — the structurally rich, shaded habitat characteristic of many small tetras across the Amazon basin. This type of microhabitat provides cover, moderate flow, and invertebrate prey, and is broadly replicated in planted aquaria designed for softwater characids.
Feeding
In the wild, Inpaichthys parauapiranga feeds on insect larvae, as recorded in the original description data. This is consistent with the diet of small insectivorous and omnivorous characids inhabiting structurally complex forest streams, where fallen insects, aquatic invertebrates, and zooplankton form the bulk of available prey.
In the aquarium the species is undemanding and accepts a range of prepared and live or frozen foods. High-quality flake, micro-pellets, and frozen foods such as Daphnia, brine shrimp, and bloodworm are all suitable. Offering varied live and frozen invertebrate foods supports condition and coloration and more closely mirrors the natural diet.
Mating
Inpaichthys parauapiranga is a small egg-scattering characid, and spawning behaviour follows the open-water pattern typical of the family: males and females scatter adhesive or semi-adhesive eggs among fine-leaved vegetation or over the substrate, with no parental care following spawning. Sexual dimorphism is present — males are slightly larger and show a dark anal-fin margin, which likely plays a role in courtship signalling.
As a schooling species, reproductive behaviour is most naturally expressed in a group setting, where males display among themselves and to females. Spawning is probably stimulated by soft, slightly acidic water, warm temperatures, and good feeding condition, in line with the softwater Amazonian environment from which the species originates.
Breeding
Tank-bred Inpaichthys parauapiranga is already available in the hobby, as noted by specialist retailers shortly after the species' formal description in 2024. The species follows the egg-scattering model common to small tetras: a conditioned pair or small group placed over a bed of fine-leaved plants or a spawning mop will scatter small adhesive eggs, which the adults do not tend and will consume if given the opportunity.
For successful rearing, spawning adults are typically separated from the eggs after spawning, or the eggs or spawning medium transferred to a dedicated rearing vessel. At temperatures in the mid-to-upper 20s Celsius, eggs hatch within a few days. The tiny fry require infusoria or commercial liquid fry food initially, graduating to newly hatched brine shrimp and finely crushed dry foods as they grow. Soft, slightly acidic water and gentle filtration support egg development and fry survival.
In the aquarium
Inpaichthys parauapiranga is described by hobby sources as peaceful, active, and easy to maintain, and best kept in groups of six or more individuals that allow natural schooling and social interaction. A planted aquarium with areas of open swimming space, dim to moderate lighting, and some surface cover replicates the shaded forest-stream environment and shows the species at its best.
Water chemistry should lean toward soft and slightly acidic: pH 6.0–7.5, with temperatures of 73–82 °F (74–82 °F). These parameters reflect both the collection-site data (79 °F, pH 6.5) and the broader range recommended by hobbyist sources for long-term maintenance. Tankmates should be similarly small and peaceful — other small characids, dwarf cichlids, corydoras, and small rasboras all make suitable companions. The species is available as tank-bred stock, which is preferred over wild-caught for sustainability reasons and typically adapts more readily to aquarium conditions.
Conservation
Inpaichthys parauapiranga was described in 2024 and has not yet received a formal IUCN Red List assessment. The original description notes a Data Deficient (DD) status reflecting the limited distributional and population data available for a newly described species. No dedicated conservation assessment has been published as of mid-2026.
The rio Aripuanã basin in Mato Grosso, where the type locality lies, is part of the broader Amazon drainage system that faces ongoing pressures from deforestation, agricultural expansion, and river modification across its catchment. For a species known from a narrow stream tributary, these landscape-level changes represent a potential risk even in the absence of formal evaluation. The availability of tank-bred stock in the trade reduces demand for wild-caught individuals and is the most practical conservation contribution aquarists can currently make.