Taxonomy & naming
Aphyocharax colifax was described by Donald C. Taphorn and James E. Thomerson in 1991 from material collected in Venezuela. The valid name, as recorded in Eschmeyer's Catalog of Fishes (Catalog of Fishes, CAS), is Aphyocharax colifax Taphorn & Thomerson, 1991. A subsequent taxonomic revision of Aphyocharax avary and related species published in ZooKeys (Pensoft) confirmed the species' status and current placement.
The genus Aphyocharax belongs to the subfamily Aphyocharacinae within the large family Characidae. It is a group of small, schooling characins that share a tendency toward brilliant red or orange caudal-fin pigmentation — a trait that made the bloodfin tetra (Aphyocharax anisitsi) one of the earliest tetras established in the hobby. Lima (2003), in the Checklist of the Freshwater Fishes of South and Central America (Reis, Kullander & Ferraris, eds.), treated the subfamily and provided the framework within which colifax is currently classified.
Morphology
Aphyocharax colifax is a slender, laterally compressed characin reaching a maximum recorded size of 2 in standard length for males and unsexed specimens. Like its congeners, the body is elongate and streamlined, suited to fast, open-water movement. The fins are proportionally delicate; the caudal fin is forked and, as implied by the species name, bears the bright-red coloration that characterises the genus.
Detailed published meristic data for this species are sparse in accessible literature. The general Aphyocharax body plan features a prominent lateral line, small scales, and a small mouth oriented for mid-water feeding. Sexual dimorphism has not been formally described in detail for this species, though size and fin coloration differences between sexes are typical for the genus.
Habitat
Aphyocharax colifax is native to South America, specifically the Orinoco River basin in Venezuela. FishBase characterises its ecological guild as benthopelagic — occupying both the lower water column and open mid-water — in freshwater, tropical conditions. The Orinoco system encompasses a vast mosaic of rivers, flooded savannahs (llanos), gallery forests, and blackwater tributaries, and Aphyocharax species within this basin are typically found in slower reaches, marginal vegetation zones, and flooded-plain pools rather than swift main-channel currents.
The tropical climate of the Venezuelan Orinoco drainage imposes a marked seasonal flood pulse: water levels and chemistry shift dramatically between wet and dry seasons, influencing the availability of food, spawning cues, and shelter. Small characins such as A. colifax are well adapted to exploit the seasonally flooded margins when invertebrate prey is most abundant.
Feeding
Aphyocharax colifax is an omnivore in the broad characin mould, foraging opportunistically on small aquatic invertebrates, insect larvae, zooplankton, and surface-fallen insects in its natural habitat. Its slender, mid-water body plan and small, upturned mouth are consistent with a diet dominated by planktonic or near-surface prey.
In the aquarium, congeners such as A. anisitsi and A. rathbuni are accepted as undemanding feeders that take high-quality flake and small pellets readily alongside frozen or live foods such as Daphnia, Artemia, and bloodworm. These feeding habits can be reasonably applied to A. colifax, with a varied diet that includes live or frozen invertebrate food recommended to maintain condition and support breeding.
Mating
Aphyocharax species are egg-scattering characins with no parental care, and reproductive behaviour in A. colifax is expected to follow the open-spawning pattern typical of the genus. Males court females with active chasing and fin displays, the bright red caudal colouring likely serving as a visual signal during courtship. Pre-conditioning with nutritious live or frozen food brings both sexes into breeding condition more reliably.
Spawning occurs in open water or among fine-leaved vegetation, where adhesive or semi-adhesive eggs are scattered. The adults do not guard or attend the spawn and will readily consume eggs given access to them, so breeders typically separate adults after spawning or provide a fine-mesh grid over the tank bottom to protect falling eggs.
Breeding
Like other members of the genus, Aphyocharax colifax is presumed to be a relatively straightforward egg-scattering tetra to breed under appropriate aquarium conditions. A separate, dimly lit breeding tank furnished with fine-leaved plants or spawning mops, slightly acidic to neutral water, and a temperature in the upper range of the species' tolerance supports conditioning and spawning. Pre-conditioning with live or high-quality frozen foods — Daphnia, newly hatched Artemia, small bloodworm — brings adults into spawning condition within a few days.
Eggs are scattered among the spawning medium and are adhesive enough to cling briefly to plant leaves or mop fibres. Incubation at tropical temperatures is typically 24–36 hours for close relatives, with fry becoming free-swimming within a few days of hatching. First foods are infusoria or commercial liquid fry food, graduating to freshly hatched Artemia nauplii as the fry grow. Adults must be removed after spawning to prevent predation of the eggs.
In the aquarium
Aphyocharax colifax is not a widely traded species in the hobby and aquarium records are limited; most available husbandry guidance derives from experience with congeners such as the bloodfin tetra. As a schooling fish it should be kept in groups of six or more, in a moderately sized aquarium with open swimming space and subdued to moderate lighting. A planted tank with soft substrate and gentle filtration suits the species' benthopelagic, vegetation-associated habits.
Water chemistry should reflect the tropical, soft-to-moderately-hard conditions of the Venezuelan Orinoco lowlands: temperatures broadly in the 73–82 °F range, pH near neutral to mildly acidic, and low to moderate hardness. These fish are active and fast-moving; peaceful community tankmates of similar size — other small tetras, small rasboras, corydoras — work well. Live and frozen foods should form a regular part of the diet to maintain colour and health. Because the species is uncommon in the trade, captive-bred stock should be sought where possible.
Conservation
Aphyocharax colifax is assessed as Least Concern (LC) on the IUCN Red List, with the assessment carried out on 1 August 2017. This status reflects a species with a sufficiently broad distribution in the Orinoco River basin that no immediate threat to its continued survival has been identified at the time of assessment. The Orinoco basin, though subject to ongoing pressures from agriculture, oil extraction, and deforestation in parts of its range, remains one of the most hydrologically intact large river systems in South America, supporting diverse freshwater fish communities.
As with many small, schooling characins from lowland South American rivers, A. colifax is not known to face acute or immediate threats, though broader changes to the Orinoco floodplain hydrology and water quality remain long-term concerns for the region's freshwater biodiversity as a whole.