Taxonomy & naming
Hyphessobrycon takasei was described by the French ichthyologist Jacques Géry in 1964. The type locality given in the original description is Serra do Navio, above Macapá in the then Amapá Territory of north-eastern Brazil, within the Araguari River drainage. Eschmeyer's Catalog of Fishes records the valid name as Hyphessobrycon takasei Géry, 1964, and the species remains placed in Hyphessobrycon.
Hyphessobrycon is the largest genus of characids and one of the most species-rich in the entire order Characiformes, encompassing a morphologically diverse assemblage united broadly by small size, a prominent humeral or mid-lateral spot, and the presence of a Weberian apparatus. The placement of many species within Hyphessobrycon has been debated as molecular and morphological phylogenies have revised the broader Characidae, and the genus is widely acknowledged to be polyphyletic in its current circumscription; revisions continue to separate out lineages. H. takasei has not been a focus of revisionary work and remains in Hyphessobrycon pending a broader reclassification of the group.
The specific epithet honours its collector or a contemporary associate; the name takasei does not appear to derive from a descriptive Latin or Greek root but is an eponym. The common name coffee-bean tetra refers straightforwardly to the prominent, rounded dark blotch on the flank that resembles a roasted coffee bean.
Morphology
Hyphessobrycon takasei is a small, moderately deep-bodied characid reaching approximately 1 in standard length, with a reported maximum of around 1.5 in. The body is laterally compressed in the typical Hyphessobrycon manner, with a rounded dorsal profile and a relatively deep mid-body that tapers toward the narrow caudal peduncle.
The most diagnostic feature is a large, dark, roughly oval blotch positioned on the mid-lateral flank, usually centred at or just behind the mid-body; it is this mark that inspired the common name. The flanks are otherwise silvery to pale gold, sometimes with a faint lateral stripe, and the fins are largely hyaline or with a light flush. A small humeral spot may also be present anterior to the main blotch. Like most Hyphessobrycon, the species shows a small adipose fin between the dorsal and caudal.
Sexual dimorphism is subtle. Females in breeding condition are noticeably deeper-bellied and somewhat fuller than males when viewed from above, a feature used to distinguish conditioned pairs. Males may be slightly slimmer and more intensely coloured under good conditions, but the differences are modest compared with more strongly dimorphic relatives.
Habitat
Hyphessobrycon takasei is recorded from the Araguari River basin of north-eastern Brazil (Amapá state) and from the Oyapock River system of French Guiana. Both drainages flow through lowland Amazonian forest and coastal plain habitats in the Guiana Shield transition zone. The Araguari drains north-westward into the Atlantic near the Amazon delta region, and the Oyapock forms the border between Brazil and French Guiana.
Like most small forest-stream tetras, H. takasei likely inhabits slow-moving to standing waters: shaded tributaries, marginal pools, flooded forest margins, and similar habitats where currents are gentle, leaf litter accumulates, and tannins from decaying vegetation create soft, acidic, darkly stained water. Source data indicate a natural temperature range around 75–77 °F, with pH approximated near 6.5 and soft to moderately hard water chemistry. These conditions reflect the typically blackwater or mixed-water environments of north-eastern Amazonian lowland streams, where humic acids from forest soils dominate the chemistry.
Feeding
Hyphessobrycon takasei is an omnivore in the wild, feeding opportunistically on small invertebrates, insect larvae, zooplankton, and organic detritus in the water column and at the surface. This feeding mode is typical of small characids inhabiting forest streams, where seasonal flooding concentrates or disperses food resources and a generalist strategy is advantageous.
In the aquarium it accepts a wide range of prepared and live foods without difficulty. High-quality micro-pellets and fine flake form a practical staple, and the fish benefits from regular supplements of small frozen or live foods — bloodworm, mosquito larvae, brine shrimp, and Daphnia are all readily taken and improve colour and conditioning. Because of its small mouth, food particle size matters: coarsely ground or large pellets may be ignored or difficult to ingest. Feeding small amounts two to three times daily is preferable to one larger meal.
Mating
Hyphessobrycon takasei is an egg-scattering characid with no parental care, a reproductive mode shared across the great majority of small Hyphessobrycon species. Males pursue females through the aquarium with increased activity as conditioning improves; visible courtship is brief and characterised by parallel swimming and lateral displays between prospective partners rather than the prolonged, ritualised displays seen in cichlids or gouramis.
The species spawns most readily in soft, slightly acidic water at temperatures in the mid-20s Celsius, conditions that mimic the natural blackwater or mixed-water environment of north-eastern Amazonian drainages. Conditioning the group on varied live and frozen foods noticeably increases readiness to spawn, and females will visibly fill out with eggs when in good condition. Spawning activity in a community tank is largely nocturnal or crepuscular and easily goes unnoticed unless a separate breeding setup is used.
Breeding
To breed H. takasei deliberately, a small, separate aquarium is recommended — a tank of 10–15 US gal is ample. Water should be soft (up to about 8 dH) and acidic to neutral (pH 5.5–7.0), with temperature in the 75–81 °F range and subdued lighting. Fine-leaved plants such as Java moss, hornwort, or synthetic spawning mops provide the substrate into which eggs are scattered and to which some adhere.
A conditioned pair or small group introduced to the breeding tank in the evening will typically spawn in the early morning hours. Eggs are small and semi-adhesive, scattered among plant material and settled on the substrate. Because adults consume eggs at every opportunity, the spawning medium or the adults themselves should be removed promptly after spawning is observed. Eggs hatch within approximately two to three days at breeding temperature, and the tiny free-swimming fry require infusoria or commercial liquid fry food as first foods before transitioning to freshly hatched brine shrimp nauplii and finely powdered preparations. Water quality in the rearing vessel must be maintained carefully, as fry are sensitive to dissolved wastes. Growth to juvenile size takes several weeks under good conditions.
In the aquarium
The coffee-bean tetra is a peaceful, sociable, and undemanding species well suited to a planted community aquarium. It is best kept in a group of at least six individuals, as the shoaling instinct is strong and solitary or small-group specimens are shy and less active. In a proper shoal the fish gain confidence, display more openly, and provide a more rewarding visual effect as the dark mid-lateral blotches of each fish align and catch the light together.
Water parameters should be soft to moderately hard (up to about 8–10 dH), slightly acidic to neutral (pH 5.5–7.0), and maintained in the 75–82 °F range. A well-filtered, planted tank with some shading from floating plants or dense background planting closely mimics the fish's forest-stream origins and shows its best colours. It mixes well with other small, peaceful species of similar size — other small Hyphessobrycon, Nannostomus pencilfish, small Corydoras, and similarly sized rasboras are all compatible. Avoid fast-moving or aggressive tankmates that will out-compete it at feeding or nip its fins.
The species is hardy once established and tolerates routine aquarium maintenance well. Its small size, peaceful disposition, and ease of breeding make it a rewarding choice for aquarists who want a less-common tetra with genuine character.
Conservation
Hyphessobrycon takasei was assessed as Least Concern (LC) by the IUCN Red List in March 2021. The assessment reflects a distribution across two drainages in north-eastern Brazil and French Guiana, with no evidence of rapid population decline sufficient to qualify for a threatened category under current criteria.
The Araguari and Oyapock basins span a region that retains substantial forest cover but also faces ongoing pressure from agricultural expansion, gold mining, and infrastructure development in the Guiana Shield and Amapá region. As a small, widespread characid of forest streams, H. takasei is likely affected by the same broad habitat pressures that concern regional ichthyologists, though it has not been identified as particularly vulnerable at the species level. Most aquarium specimens are tank-bred, which relieves any collecting pressure on wild populations. No dedicated conservation programmes are known for the species.