Taxonomy & naming
The genus Hemichromis was erected by Wilhelm Peters in 1858 for a Chromis-like West African cichlid (the type species being the large piscivore Hemichromis fasciatus), characterised by highly protrusible jaws and a buccal dentition of unicuspid teeth with anteriorly placed pseudo-canines. The American ichthyologist Theodore Gill monographed the genus in 1862, and in that paper described Rubricatochromis bimaculatus from a single specimen of unrecorded provenance — Eschmeyer's Catalog of Fishes records the type locality as 'No locality, probably Liberia', with the holotype (USNM 4097) in the Smithsonian. Gill noted that the new fish's smaller mouth, less protractile jaws and different colour pattern set it apart from the other Hemichromis, but kept it in the genus on the strength of its similar tooth arrangement. Even at the time the placement was contested — Thys van den Audenaerde later suggested bimaculatus warranted its own genus — but most workers (Regan, Loiselle, Greenwood) accepted the monophyly of Hemichromis through the twentieth century.
The name became one of the hobby's great muddles. Following Boulenger's drastic 1915 lumping, almost every small red jewel cichlid was filed under bimaculatus, and by the late 1960s aquarists and biologists alike had realised that several biologically distinct animals were being traded under the one nomen. Paul V. Loiselle resolved the tangle in his 1979 revision of the genus (published as a four-part series in the Annales du Musée Royal de l'Afrique Centrale), which redefined bimaculatus narrowly, rehabilitated Hemichromis guttatus, Hemichromis elongatus and Hemichromis letourneauxi, and described four new species including Hemichromis lifalili. Loiselle's central, often-repeated finding is that virtually all pre-1979 articles purporting to deal with 'Rubricatochromis bimaculatus' — in both the aquarium and the scientific literature — actually refer to Hemichromis guttatus, the first jewel cichlid imported (to Germany, in 1911). Most recently, Lamboj & Koblmüller's 2022 molecular phylogeny split the brilliantly red, spangled species into a new genus, Rubricatochromis ('red-coloured cichlid'), so that FishBase and the Catalog of Fishes now list this fish as Rubricatochromis bimaculatus (Gill, 1862); the IUCN and much of the literature still use the long-familiar Rubricatochromis bimaculatus, retained here.
Morphology
Rubricatochromis bimaculatus is a moderately deep-bodied, fusiform cichlid that reaches about 5.5 in in standard length, though a common length nearer 3–3.5 in is more usual and captive fish are often cited at around 4.5 in — a small-to-medium cichlid. The fins carry 14–15 dorsal spines and 10–12 soft rays, with 3 anal spines and 8–9 soft anal rays. Its specific name, 'two-spotted', is something of a misnomer in practice: the diagnostic pattern is three black blotches down each side — one on the gill cover, one at the midpoint of the flank, and one at the base of the tail — set against a ground colour that shifts from a quiet brownish-grey in unstressed fish to an intense scarlet over the lower head, breast and belly when a fish is in breeding condition or dominance display.
What most cleanly separates the true bimaculatus from its glittering relatives is what it lacks. In Loiselle's key the species is diagnosed in part by the proportions of the lower pharyngeal bone, but for the living fish the telling feature is that the body is 'almost totally devoid of metallic blue or gold spangling' — the iridescent 'jewels' that stud the flanks and fins of Hemichromis guttatus, Hemichromis lifalili and Hemichromis cristatus are reduced here to a faint scatter at most. A genuine bimaculatus is therefore a comparatively plain red-and-black fish, not the sequinned showpiece the trade name promises. Sexual dimorphism is modest and unreliable: males average slightly larger and may show longer, more pointed dorsal and anal fins, while ripe females are rounder-bodied and often flush a deeper, more saturated red, but the sexes are otherwise difficult to tell apart outside of breeding.
Habitat
The true Rubricatochromis bimaculatus is a fish of the Upper Guinean forest streams of westernmost Africa. Loiselle restricted its range to Guinea, Sierra Leone and Liberia (FishBase, following Lévêque and colleagues, gives the same narrow limits), although broader nineteenth- and twentieth-century records spreading it across much of West Africa and beyond almost all rest on misidentified Hemichromis guttatus or other congeners; FishBase explicitly flags that 'species boundaries in the genus remain unclear.' Within its restricted range it lives some distance inland from the coast, in clear forest streams, mud- and sand-bottomed canals and small rivers associated with areas of intact or recently disturbed forest cover.
These are soft, warm, slightly acidic to neutral waters. FishBase gives a preferred pH of about 6.5–7.5 and a temperature band of roughly 70–73 °F — cooler than many tropical aquarium cichlids, reflecting the shaded forest-stream biotope — with a tolerated hardness of about 4–16 dH. The species is potamodromous and occurs in both fresh and, occasionally, mildly brackish reaches near the coast. As shallow shoreline and channel dwellers, jewel cichlids keep to the upper few metres of the water column; published in-situ depths are not well documented, but the small, structurally complex streams they inhabit confine them to roughly the top 3–7 ft. They shelter and spawn among rocks, roots, leaf litter and submerged wood.
Feeding
Jewel cichlids are opportunistic carnivores and omnivores that forage over the bottom and through structure for small animal prey. In the wild the diet centres on aquatic insects and their larvae, small crustaceans and other invertebrates, supplemented by worms, tiny fishes and incidental plant and detrital matter; FishBase places the species at a relatively high trophic level (around 3.9), consistent with a predominantly animal diet. The protrusible jaws and conical, pseudo-canine-tipped dentition that define the genus are the tools of a grab-and-hold predator rather than a sifter or scraper.
In the stream community the jewel cichlid functions as a small mid-level predator of the benthos and margins, hunting among rocks, leaf litter and root tangles. The same boldness and adaptability that make it an effective forager also make it a successful colonist: introduced populations (in Florida and the Philippines, derived largely from the spangled trade species rather than true bimaculatus) have established readily, and the genus has a reputation for displacing or preying on smaller native fishes where it has been released.
Mating
Rubricatochromis bimaculatus is a monogamous, biparental species, and pair formation is the pivot of its social life. Outside breeding the fish are gregarious but quarrelsome; as a pair comes into condition it withdraws from the group, claims and clears a territory around a chosen spawning surface, and becomes intensely aggressive toward everything else, conspecific or not. Courtship is built on the genus's vivid colour signalling — both partners intensify to a deep red, displaying flanks and fins to one another with lateral spreads, quivering and mouth-to-mouth jaw-locking trials of strength that establish the bond and synchronise the pair.
This is also where the species earns its difficult reputation. The same hair-trigger aggression that lets a pair defend a brood against far larger fish is turned on a mate the moment the bond falters: an unready or mismatched partner is harried mercilessly and can be killed. Keepers traditionally counter this by raising a group of young together and letting a pair form naturally, by giving the tank enough length and broken sight-lines for a subordinate to escape, and by being ready to separate fish that have not genuinely paired. A settled, well-matched pair, by contrast, can be a strikingly coordinated unit that holds a territory and raises brood after brood together.
Breeding
The jewel cichlid is a textbook biparental open-substrate (open-brooding) spawner — the reproductive strategy that defines the genus. The pair selects and meticulously cleans a firm surface, typically a flat or gently angled rock, a broad leaf or a patch of cleared substrate; where no suitable hard surface is available the fish will excavate a shallow pit in the sand or gravel and spawn in it. The female lays rows of adhesive eggs over the cleaned surface and the male follows immediately to fertilise them, the two working in alternating passes over a period of up to two or three hours.
Clutches are large for the fish's size. Hobbyist accounts of the trade jewel cichlids report anywhere from about 200 to several hundred eggs in a single spawn — FishBase's congener data note up to roughly 300 eggs hatching after about two days, with the fry free-swimming after about five — and exceptional spawns approaching 500–800 eggs have been recorded. Both parents share the work intensively: the eggs are fanned and guarded against all comers, infertile eggs (which whiten) are picked out and eaten, and after hatching the wriggling larvae are shuttled to one or more pits and moved among them. The fry become free-swimming within roughly three to five days of hatching and are then led about the territory as a tight grey cloud, one parent at the front and the other shepherding stragglers. Parental defence is fierce and prolonged, often continuing while the next clutch is already on the way; pairs typically spawn repeatedly, every few weeks, when well fed.
In the aquarium
The jewel cichlid is one of the oldest and most widely kept African cichlids in the hobby, and an excellent fish — for the right keeper. It is hardy, undemanding about water chemistry, brilliantly coloured in breeding dress, and a tireless, attentive parent. It is also genuinely belligerent, and the single most common mistake is underestimating that aggression: a breeding pair will dominate, harass and frequently kill tankmates many times their size, and is entirely capable of clearing a community tank. This is not a community fish.
A single pair needs a tank of at least about 39.5 in length (roughly 200+ litres); more length is better, both to dilute aggression and to let a non-breeding fish keep its distance from a hostile mate. FishBase's husbandry note is blunt: aggressive, keep in pairs, minimum aquarium 39.5 in. Water parameters are easy — these fish thrive across a broad range, with a pH around 6.5–7.5 and moderate hardness suiting them well; aim for the species' naturally warm-but-not-hot regime (the mid-20s °C, around 75–82 °F for breeding, is typical hobby practice, a touch above the cool wild figure). Provide rockwork, driftwood and caves to break the tank into defensible zones and give weaker fish refuge, plus at least one flat rock as a potential spawning site. Robust or floating plants survive better than delicate rooted ones, which a digging pair will uproot.
Feeding presents no difficulty: jewel cichlids accept virtually all foods and do best on a varied carnivore-leaning menu of quality pellets or flake supplemented with live and frozen items — bloodworm, brine shrimp, daphnia and the like — which also bring out the best colour. The standard advice on tankmates is to keep a pair alone, or to attempt them only with similarly robust, fast cichlids or large characins in a spacious tank, accepting that compatibility may collapse the moment the pair spawns. A final, important caveat for the discerning keeper: a fish bought as 'Rubricatochromis bimaculatus' is, statistically, almost certainly Hemichromis guttatus or Hemichromis lifalili — visibly more spangled with blue-green than the genuinely rather plain true bimaculatus — and the true species, restricted to a few West African countries, only sporadically reaches aquarists. Husbandry is effectively identical across the group, but the name on the label rarely is.
Conservation
The IUCN Red List assesses Rubricatochromis bimaculatus as Least Concern (assessed 2020 by Dankwa, Azeroual and Lalèyè; the assessment retains the traditional binomial), with an unknown population trend. As a small, adaptable and fecund fish across its West African range, it faces no species-level threat at present and is of no fisheries interest. It is harmless to humans and is not listed by CITES or CMS.
The more meaningful conservation context is twofold. First, the taxonomic confusion that dogs the genus means range and abundance data for the true bimaculatus are genuinely uncertain — many records belong to other species — and FishBase notes outright that species boundaries within Hemichromis remain unclear, which complicates any fine-grained assessment of this particular fish. Second, its Upper Guinean forest-stream habitat in Guinea, Sierra Leone and Liberia is among the more heavily pressured freshwater landscapes in Africa, where deforestation, alluvial and artisanal mining, siltation and pollution are degrading the small clear streams these fish depend on. None of this is flagged as a present danger to the species, but the hardiness that makes the jewel cichlid an invasive elsewhere is also what currently insulates it from the pressures on its native waters.