Taxonomy & naming
Geophagus multiocellus was described in 2018 by the Brazilian ichthyologists José Leonardo de Oliveira Mattos and Wilson J. E. M. Costa, in the open-access journal Zoosystematics and Evolution, in a paper erecting three new eartheaters from the coastal basins of north-eastern Brazil (the others being Geophagus rufomarginatus of the Rio Buranhém and Geophagus santosi of the Rio Mariana). The species name is built from the Latin multum, 'many,' and ocellus, 'little eye' or 'jewel,' in allusion to the numerous small pale-blue spots with minute bright-blue centres scattered over its flanks. Eschmeyer's Catalog of Fishes, FishBase and the Catalogue of Life list it as valid as Geophagus multiocellus Mattos & Costa 2018. It belongs to the 'Geophagus' brasiliensis species group, the eastern-Brazilian pearl-cichlid lineage, which is distinct from the true Amazonian-Guianan eartheaters and is widely expected to be moved to its own genus when the genus is revised — hence the frequent 'Geophagus' in quotation marks — though the combination Geophagus multiocellus is the valid name. The describing study's phylogeny places multiocellus in a clade with Geophagus santosi and the older Geophagus itapicuruensis, spanning the Rio de Contas, Rio Itapicuru and Rio Mariana basins. The holotype (UFRJ 11764, 4 in SL) was collected at the Rio Cambiriba, in the Rio Gongogi drainage of the Rio de Contas basin, at Iguaí, Bahia.
Morphology
Geophagus multiocellus is a small-to-medium eartheater; FishBase gives a maximum of about 4 in in standard length, and the holotype measured 4 in SL. It has the brasiliensis-group form — a moderately deep, laterally compressed body, a fairly steep frontal profile and the small, low, protrusible mouth of a substrate-sifter — together with the genus-typical dark mid-lateral blotch. Its diagnostic feature, and the source of its name, is its colour pattern: it is distinguished from all other species of the brasiliensis group by having numerous small pale-blue spots, each with a minute bright-blue dot at its centre, scattered densely over the flanks — a finer, more profuse and more sharply 'ocellated' spangling than the streakier patterning of its relatives. Against an olive-to-grey or brassy ground these jewel-like spots extend onto the cheeks, operculum and unpaired fins and brighten in dominant and breeding fish. Sexual dimorphism is modest in the group: males grow somewhat larger and may show marginally extended fin tips, with the sexes least distinguishable outside breeding condition.
Habitat
The species is endemic to the Rio de Contas basin of Bahia, north-eastern Brazil, known from the Rio Gongogi sub-drainage (including the Rio Cambiriba) and from streams in the upper basin around Iguaí, Nova Canaã and Poções, at altitudes recorded between roughly 270 and 1788 ft above sea level. The Rio de Contas is one of the medium coastal rivers of Bahia, rising in the interior uplands and running east to the Atlantic; the reaches multiocellus occupies are clear-to-tannic streams and small rivers flowing over sand, gravel and rock in a hilly, transitional landscape between the Atlantic Forest and the drier interior. It is a benthopelagic freshwater fish of warm tropical waters. No specific published temperature or chemistry envelope exists for the species, but the upland Rio de Contas regime is warm, moderately soft, and ranges from clear to lightly stained over a hard, mixed bottom — the sort of running-water, mixed-substrate habitat its sifting habit exploits. Its confinement to this one basin is part of the broader basin-by-basin endemism that characterises the brasiliensis complex along eastern Brazil.
Feeding
Like all members of its genus and group, Geophagus multiocellus is a substrate-sifter. It takes mouthfuls of sand and fine sediment from the stream bed, sorts edible invertebrates, detritus and organic particles from the inorganic grit over its gill rakers, and expels the cleaned substrate through mouth and gills. The brasiliensis-group eartheaters are abundant sand-sifting fishes whose diet runs to benthic invertebrates — insect larvae, small crustaceans and worms — along with seeds, plant fragments and detritus, placing them low on the food web as invertivore-detritivores. There is no diet study specific to multiocellus, but its mouth and gill-raker morphology and its group membership make it a near-certain sand-sifter, working the productive interface of sand, gravel and leaf litter in the Rio de Contas streams.
Mating
The 'Geophagus' brasiliensis species group are biparental substrate spawners and guarders rather than mouthbrooders — the reproductive mode that separates them from the Amazonian-Guianan true eartheaters and from the Andean-Panamanian maternal mouthbrooders. The reproductive biology of multiocellus has not been observed and is inferred from this well-documented group. A male and female form a pair, clean a spawning surface — a flat stone or firm patch of substrate — and defend a territory around it together, with the usual cichlid courtship of lateral displays, fin-spreading and joint substrate-cleaning. The eggs are laid and tended in the open, with both parents sharing care and defence; there is no oral incubation. This robust, conventional biparental substrate-spawning is the reproductive signature of the group and a large part of why its best-known member, the pearl cichlid, is so adaptable.
Breeding
No captive or wild breeding account exists specifically for Geophagus multiocellus; what follows is the group pattern, exemplified by the pearl cichlid. The pair lays a clutch of adhesive eggs on a cleaned hard surface and tends them biparentally — the female fanning and directly caring for the eggs, the male defending the perimeter. After hatching, the wrigglers are typically moved to one or more pre-dug pits, and once free-swimming the fry are herded and guarded as a school by both parents, which defend them tenaciously. Brasiliensis-group cichlids produce sizeable broods relative to the mouthbrooding eartheaters; multiocellus, being on the small side at around 4 in, presumably produces correspondingly modest clutches, but no counts have been published for it. Spawning in coastal-basin cichlids of this kind typically tracks the wet season, when the rivers fill and feeding improves, and the group's hardy, attentive parental care extends well past hatching. The clouds of fine blue-spotted fry of a species like this would, if ever bred in aquaria, be a striking sight, but the species has not to public knowledge been raised in captivity.
In the aquarium
Geophagus multiocellus is unknown in the aquarium hobby. It was described only in 2018, comes from a Bahian river system that is not a source for the ornamental trade, and has no established body of aquarist breeding reports. The brasiliensis-group eartheater hobbyists actually keep is the hardy, widely available pearl cichlid, and any husbandry guidance for multiocellus is extrapolated from it.
That extrapolation is reasonably safe, because the brasiliensis group is among the most forgiving of eartheaters. A keeper would provide a spacious tank with a deep bed of fine, soft sand — these are substrate-sifters, and gravel both frustrates feeding and risks gill abrasion — with scattered smooth stones, driftwood, gentle current and open foraging space, reflecting the running, mixed-substrate upland streams the species comes from. Warm water (around 75–82 °F) of soft to moderate hardness suits it; the group tolerates a wide range, so clean, stable, well-filtered conditions matter more than precise targets, and a constant sand-stirrer rewards strong mechanical filtration and regular water changes. Feeding is straightforward — sinking pellets and frozen or live invertebrates taken off the bottom match the natural invertivore-detritivore diet. The usual caution applies to temperament: brasiliensis-group cichlids can become territorial and pugnacious when breeding, so even this small, finely spotted species would want space and the option to hold a defensible territory.
Conservation
Geophagus multiocellus has not yet been formally evaluated for the IUCN Red List (Not Evaluated), which is unsurprising for a species described only in 2018. As a single-basin endemic of the Rio de Contas, however, it fits the profile of a fish that warrants conservation attention. The Rio de Contas basin, like the other coastal rivers of Bahia, faces pressures from water abstraction and damming, agriculture and cattle ranching, deforestation, sedimentation, pollution and the introduction of non-native fishes, and lies in a region exposed to intensifying drought. Narrow-range upland endemics of this kind are inherently vulnerable to localised disturbance of their few occupied streams. The rapid recent description of multiocellus and its relatives underlines how much undescribed and unassessed diversity these north-eastern Brazilian basins still hold, and how exposed it is. A formal assessment of multiocellus and the other newly described Bahian eartheaters would be a sensible priority. The species has no CITES listing and no commercial or ornamental significance.