Taxonomy & naming
The species was described by the Austrian ichthyologist Johann Jakob Heckel in 1840 as Heros coryphaenoides, from the Rio Negro at Maribitanos, in what is now Amazonas, Brazil; the unique holotype (NMW 17376) is held at the Naturhistorisches Museum Wien. In the same 1840 work Heckel also named Heros niger from the same fauna, a name that — together with Centrarchus niger Jardine 1843, Cichlasoma arnoldi Ahl 1936, and Chuco axelrodi Fernández-Yépez 1971 — is now treated as a junior synonym. For most of the twentieth century the "chocolate cichlids" drifted through a tangle of names within the catch-all genus Cichlasoma, and the hobby literature applied several interchangeably, making identification genuinely difficult. That confusion was resolved when Sven O. Kullander (1986), in his monograph on the cichlids of the Peruvian Amazon, erected the genus Hypselecara and recognized just two species: Hypselecara temporalis (Günther 1862) and Hypselecara coryphaenoides (Heckel 1840). Kullander folded H. goeldii, H. crassa, and H. hellabrunni into the former and Heros niger, H. arnoldi, and Hyphessobrycon axelrodi into the latter. The genus sits in the Neotropical subfamily Cichlinae (heroine cichlids), alongside relatives such as Heros, Hoplarchus, and Mesonauta; Kullander remains the FishBase coordinator for the species, and his 2003 Checklist of the Freshwater Fishes of South and Central America is the standard nomenclatural treatment.
Morphology
Hypselecara coryphaenoides is a large, laterally compressed, deep-bodied cichlid. FishBase gives a maximum of 6.5 in standard length, with a maximum total length of about 8.5 in; aquarium fish are reported to reach roughly 8–10 in TL under good conditions, though they mature and spawn well below that ceiling. The two members of the genus are easily told apart: Hypselecara temporalis has an almost square, abruptly steep-headed profile and is typically a green-and-wine-red fish carrying its dark lateral blotch below the lateral line, whereas Hypselecara coryphaenoides is more elongate, with a gradually rising forehead, and is dark brown to black with its lateral blotch centred above the lateral line and extending into the base of the soft dorsal fin. The epithet captures that head shape — coryphaenoides means "resembling Coryphaena," the dolphinfish, an allusion to the tall, blunt, dolphinfish-like head. Identification is complicated by two things: Hypselecara temporalis is itself geographically variable, and Hypselecara coryphaenoides undergoes dramatic, mood-driven changes in colour and pattern, shifting from a quiet uniform brown to an intense black body with a glowing burnt-orange dorsal blaze when breeding or alarmed. Juveniles wear a series of brownish-black vertical bars crossed by a pale orange stripe running from the snout over the head to the soft dorsal, a pattern that fades to plain brown with the prominent flank blotch as the fish grows. Sexual dimorphism is subtle and emerges mainly at breeding: Lee Newman, who raised wild fish, found males grew slightly larger and developed a slight nuchal hump, while ripe females became much heavier-bodied; the female's genital papilla (breeding tube) is notably stouter and longer than the male's thin, short one. There is no consistent colour difference between the sexes.
Habitat
The species is a fish of the northwestern Amazon and the upper Orinoco. FishBase records it from the Amazon basin in the Negro, Trombetas, Tapajós, Maués and Uatumã rivers, and from tributaries of the upper Orinoco and the Aguaro basin; Eschmeyer's Catalog of Fishes gives the distribution simply as the Amazon and Orinoco basins of Brazil, Colombia and Venezuela. It is fundamentally a blackwater animal — soft, acidic, tea-stained water stained by dissolved tannins and stripped of dissolved minerals. FishBase lists a pH range of 5.0–6.0 and a hardness of just 0.5–1 dH, at temperatures of 72–86 °F, and notes the species lives in blackwater rivers. Lee Newman, collecting on the lower Rio Negro and its tributaries (the Rio Cueiras, and islands near the confluence with the Rio Branco) during a 1996 Project Piaba expedition, found juveniles abundant in very shallow water, sheltering in cavities and rotted holes in submerged, well-worn tree trunks alongside Ancistrus catfish and palaemonid shrimp — habitat he could net by hand from a floating dock with a dipnet and flashlight. This is a structure-loving fish of the flooded blackwater margins, where waterlogged wood and leaf litter provide the cavities it uses for cover and, later, for spawning. In Newman's aquarium the colony thrived at pH 6.5, 84 °F and very soft water (calcium carbonate hardness around 4 mg/L), parameters that closely echo its wild blackwater home.
Feeding
FishBase places the species at a trophic level near 3.8, reflecting an omnivorous diet that leans more carnivorous than that of the basin's dedicated detritivores. In the aquarium it is unfussy and greedy: Newman's wild-caught juveniles immediately took live brine shrimp, frozen bloodworms, live whiteworms and small soaked cichlid pellets, and as they grew they fed eagerly on chopped earthworms, frozen Mysis and cichlid pellets. Notably, the fish are attentive to the water surface and will rise to take live mealworms and crickets, suggesting that in the wild, drifting and falling terrestrial invertebrates from the flooded forest canopy form part of the natural diet alongside aquatic insect larvae and other small invertebrates gleaned from submerged wood and litter. There is no published evidence that it is a substrate-sifter in the manner of the eartheaters it sometimes shares habitat with; rather it is a generalist mid-water and structure-oriented forager.
Mating
Outside of breeding, Hypselecara coryphaenoides is strikingly peaceful toward other species — Newman kept it for years with Satanoperca eartheaters that it essentially ignored, even at feeding time — but it is intensely intolerant of its own kind. As wild juveniles grew, aggression among conspecifics rose steadily until the colony had to be repeatedly thinned; the fish remained "remarkably indifferent" to heterospecifics throughout. Pair formation is a gradual, mutual affair: in Newman's tank two near-identical fish began to tolerate each other, spent time together under a chosen piece of wood, and drove the remaining conspecifics to the far end of the aquarium — the territory established so emphatically that one excluded fish was found dead, forced out through a gap in the lid. The pair then excavate jointly, digging a broad pit; in captivity this reached about 23.5 in square (two square feet) and took a full week to complete. During this courtship-and-construction phase the secondary sexual characters sharpen and both fish drop their breeding tubes, signalling that spawning is imminent. The species also shows a curious readiness to parent: Newman twice observed a lone fish adopt unrelated fry placed nearby, taking on full parental colouration and guarding behaviour over a floating tank of another species' young.
Breeding
Hypselecara coryphaenoides is a biparental substrate spawner that breeds in the typical heroine-cichlid fashion. After preparing a cleaned site — often the sheltered underside or backside of a piece of wood within the excavated pit — the female makes several "dry" passes before laying rows of eggs, with the male following to fertilize; Newman's pair completed a spawning in about 90 minutes. The female then fans and tends the egg plaque while the male takes over territorial defence. Because deposition occurred out of view, Newman could not count the eggs directly, but he estimated total brood size at around 300. Two days after spawning the wrigglers were moved to a fresh hollow in the wood, the parents taking turns transporting larvae mouthful by mouthful and signalling each other with lateral displays; the fry were free-swimming roughly a week after spawning, still carrying yolk. Newman's pair spawned three times in close succession, re-using the same cleaned pit. Parental care is biparental and prolonged: both fish escort the mobile fry, flick their pelvic fins to signal them, and intensify to the black-and-burnt-orange alarm pattern to cue the young to freeze motionless on the bottom — the parents gather them under cover each evening before lights-out. Free-swimming fry readily take newly hatched Artemia nauplii as a first food and grow quickly onto chopped bloodworm and crushed flake within a few weeks. The species spawns well below its maximum size, which makes it tractable in the aquarium; the main difficulty is its own aggression, so successful rearing depends on a large, heavily aquascaped tank with low conspecific density. As Newman observed, only low fish densities combined with complex shelter allow many juveniles to survive to recruit into the wider community.
In the aquarium
Hypselecara coryphaenoides demands a large tank — a minimum of 59 in (five feet) in length for a single adult pair, and considerably larger if tankmates are intended. The fish grows to roughly 8–10 in total length under aquarium conditions and is deep-bodied enough that standard-depth tanks 19.5–23.5 in front-to-back suit it far better than cramped narrow-footprint designs. Filtration should be robust to match the appetite: high-volume biological filtration and regular partial water changes are more important than any particular equipment brand. Temperature should be held between 26 and 86 °F; the species shows its best colour and activity at the warmer end of that band.
Water chemistry is critical, and the species is unforgiving of alkaline, hard conditions. This is a blackwater animal from the Rio Negro, and it should be kept in soft, acidic to neutral water — pH 5.5–6.8, hardness no more than 5–6 °dH (ideally lower), and zero tolerance for elevated nitrates or chloramine. Reverse-osmosis water blended to the target parameters and boosted with tannins (botanicals, peat filtration, driftwood) is the practical keeper approach. Newman's wild fish thrived at pH 6.5 and a carbonate hardness of around 4 mg/L, which is a useful real-world benchmark; pushing the pH above 7 or hardness above about 10 °dH is a common mistake and blunts breeding colour, suppresses spawning, and can cause long-term health decline. Acidic blackwater conditions also help suppress bacterial infections that can afflict cichlids kept in harder, more buffered water.
The aquascape should combine open bottom space with substantial structure. A sandy or fine-gravel substrate works well and allows the pair to excavate their characteristic broad pit — in Newman's tank, the spawning crater reached about 23.5 in square; the tank must have room for this without making the pit the only feature. Driftwood is essential both for cover and for water conditioning; large flat pieces of slate or smooth stone make useful spawning surfaces and should be available even if the fish ultimately choose wood over stone. Leave open swimming lanes. Strong planting is possible — hardy species such as Anubias and Java fern attached to wood will be tolerated and add tannins — but any soft-stemmed plant in the path of a breeding pair will be uprooted or shredded.
Choosing tankmates requires care on two axes. Hypselecara coryphaenoides is remarkably peaceful toward dissimilar fish of similar or larger size: Newman kept a colony alongside Satanoperca eartheaters for years without incident, and similarly sized Heros, Mesonauta, or peaceful large catfish (Pimelodella, Hoplosternum, large Ancistrus) make compatible company provided the tank is large enough that territories do not compress. Small fish — anything that fits in a 8–10 in cichlid's mouth — will be eaten, and this should be treated as a certainty rather than a risk. The species' Achilles heel is its relationship with its own kind: outside an established pair, conspecific aggression escalates steadily and can be lethal. Keeping more than one pair in the same tank requires a very large, heavily broken-up aquascape, and even then is not reliably peaceful; for most keepers, a single pair per display tank is the working arrangement.
Breeding is achievable in the aquarium and follows the biparental substrate-spawning pattern typical of heroine cichlids. The pair prepare a cleaned site — often the sheltered underside of a large piece of wood within the excavated pit — and the female lays several hundred eggs in rows while the male follows to fertilize. Both parents participate in brood care: the female fans and tends the egg plaque while the male handles territorial defence; wrigglers are moved mouthful-by-mouthful to fresh hollows in the wood, and free-swimming fry are escorted, sheltered at night, and rallied with pelvic-fin flicks and the striking black-and-burnt-orange alarm colouration. First food is newly hatched Artemia nauplii; the fry grow quickly onto chopped bloodworm and crushed cichlid crumble within a few weeks. The principal difficulty is not inducing spawning — a conditioned pair in correct water will usually manage that without intervention — but raising a large proportion of juveniles past 1 in. As the fry grow, intraspecific aggression among siblings intensifies and the tank population must be thinned progressively to prevent casualties. Selling or trading young fish at 1.5–2 in is recommended before dominance hierarchies consolidate.
Conservation
The IUCN Red List assesses Hypselecara coryphaenoides as Least Concern (assessed 19 November 2020 by Renata Guimarães Frederico, published 2020), consistent with a wide distribution across the Amazon and Orinoco basins. It carries no CITES listing and is rated harmless to humans, with low fishing vulnerability. The species is collected for the ornamental aquarium trade, though it is comparatively uncommon in exports — Newman noted that despite being readily collectable in the wild, it was absent from Manaus shipments during his trip, which he attributed to either seasonality or low demand; the chocolate cichlid usually sold is the more available, often commercially-bred Hypselecara temporalis. No species-specific threats are documented. As with all blackwater Amazonian fishes, however, the longer-term backdrop is the accelerating pressure on Amazon and Orinoco freshwaters from deforestation, mining (and associated mercury contamination), dam construction and altered flood-pulse regimes; none of these is recorded as a present danger to this particular species, but they frame the conditions under which its blackwater habitats will persist.