Taxonomy & naming
Apistogramma lineata was described in 2011 by the Colombian ichthyologists Lina M. Mesa Salazar and Carlos A. Lasso, in their monographic revision of Apistogramma in the Orinoco basin — the third volume of the Humboldt Institute's series on Colombia's continental aquatic resources. It was one of several Orinoco dwarf cichlids the two authors named in that 192-page work, alongside species such as Apistogramma intermedia, Apistogramma megaptera, and Apistogramma piaroa. The type locality is caño Garza, a small tributary of the río Atabapo in the Departamento de Guainía, Colombia (about 03°44′N, 67°34′W); paratypes came from the nearby caño Chaquita, a few kilometres away. The nomenclatural act is registered in ZooBank (989A35C9-2870-4632-91D8-6F419B4F07CB).
The name is plainly descriptive: 'lineata' is Latin for 'lined' or 'striped', a nod to the dark lengthwise band and the fine lines that run along the body and into the fins. That sets it apart from the genus's many eponymous and place-based names.
Apistogramma sits in the Neotropical subfamily Geophaginae, the eartheaters and their dwarf relatives. The genus is one of the most species-rich in South America — roughly a hundred valid species and many more undescribed — and within it, Apistogramma lineata belongs to the iniridae group of the pertensis lineage. Its closest relatives are the blackwater specialists of the upper Orinoco: Apistogramma iniridae and the undescribed trade form Apistogramma sp. 'Blutkehl' (Bloodthroat). It resembles the latter so closely that experienced keepers can struggle to tell them apart unless the fish are displaying their full markings. The species carries no formal 'A-number' in the hobbyist DATZ catalogue, and, unlike most popular Apistogramma, it has no established trade name beyond its scientific one.
Morphology
This is one of the smallest cichlids most aquarists will ever keep. The original description and FishBase give a maximum of about 1 in standard length for the largest male examined; females are smaller still. Even allowing for the extra length once the fins are counted on a wild adult, Apistogramma lineata is a genuinely diminutive fish, on a par with the tiniest members of its genus.
It is a slender, elongate Apistogramma of the iniridae-group build rather than a deep-bodied one. The defining feature, and the source of the name, is a dark longitudinal stripe running the length of the flank, overlaid by finer lines and broken vertical bars; the head often carries dark markings through the eye and across the cheek. Sexual dimorphism follows the usual dwarf-cichlid pattern but is comparatively muted. Males grow larger, more colourful, and carry more extended dorsal and caudal finnage, while females stay smaller and plainer. Wild males from the Atabapo can be strikingly red — a collector who took what may be the first live photographs of the species described netting a young male of 'exceptionally red colouration'. One quirk sets it apart from most congeners: a brooding female does not turn the intense lemon-yellow that signals maternal mood in most Apistogramma, which can make it easy to miss that she is carrying a spawn at all.
Colour and pattern vary across populations and shift with mood, lighting, and substrate, so identification leans heavily on provenance. The recurring caution from specialists is that Apistogramma lineata, Apistogramma iniridae, and Apistogramma sp. 'Blutkehl' overlap enough that a fish out of breeding dress may only be placed confidently to the iniridae group rather than to species.
Habitat
Apistogramma lineata is a narrow-range endemic of the río Atabapo, the blackwater river that forms part of the border between Colombia and Venezuela before joining the upper Orinoco near San Fernando de Atabapo. Records run from the mouth of the Atabapo upstream toward the río Atacavi, spanning both banks; a population from a lake on the lower río Matavi, a left-bank tributary of the upper Orinoco in Venezuela, has also been attributed to the species. The whole documented distribution is a short stretch of one river system.
The Atabapo is classic Orinoco blackwater — stained the colour of strong tea by dissolved tannins leaching from the flooded forest, nearly free of dissolved minerals, and strongly acidic. In-situ measurements are extreme by any standard. A field worker diving the lower Atabapo at Gualloval Vitina recorded a pH of 4.29, a conductivity of just 12 µS/cm, and a water temperature of 85 °F, and found a young Apistogramma lineata sheltering under a single leaf in a shallow granite pothole, less than a metre down. Tom Christoffersen's Apistogramma survey gives the species' water as pH 4–6 with very low mineral content. Across the seasonal cycle the temperature swings between roughly 26 and 88 °F while the water stays soft and acidic year-round; the higher figures keepers quote (around 82–88 °F, or the low-to-mid 80s °F) reflect dry-season extremes rather than a requirement.
The biotope is shallow shoreline among submerged granite, leaf litter, and the margins of seasonally flooded forest. At high water the sandy bottom can lie several metres down, but the fish themselves keep to the shallow, leaf-strewn edges. It shares this water with other small blackwater specialists — the cichlid Mesonauta egregius was seen in slightly deeper water nearby.
Feeding
Like the rest of its genus, Apistogramma lineata is a micro-predator of the leaf litter and soft sediment. No dedicated gut-content study of this species has been published, but its ecology matches the iniridae group generally: it works the bottom and the litter layer for small invertebrates — insect larvae, micro-crustaceans, and other tiny prey — picking through detritus rather than grazing algae or sifting sand in bulk. FishBase places it at an estimated trophic level of about 3.2, the modest-carnivore figure typical of the genus.
In the aquarium it readily takes small live and frozen foods — newly hatched brine shrimp, micro-worms, and the like — and keepers report adults and young hunting tiny shrimp and brine shrimp among the leaves. In its blackwater community it is a low-level forager and prey for larger fish itself, which fits its cryptic, cover-bound habits in the wild.
Mating
Apistogramma lineata is, like most of its genus, a polygynous harem brooder in structure: a dominant male holds a territory that overlaps the smaller territories of one or more females, each of whom defends her own spawning site. In practice, keepers describe it as one of the gentler dwarf cichlids. Where many Apistogramma males relentlessly harry females and patrol every corner of the tank, breeders of Apistogramma lineata report a male and female that often keep to opposite ends of the aquarium, with only occasional, low-intensity sparring — one keeper called it 'not too friendly, not too aggressive, just right'. The same keeper noted that the species does not seem to form the tight, conspicuous pair bond of some congeners, and that aggression eased markedly within the first week of cohabitation.
Courtship and territoriality centre on a cave or sheltered cavity that the female adopts as a spawning site. Because the fish is small and the markings that distinguish it show best during display, much of its mating behaviour — the lateral displays between rival males, the female's solicitation — is bound up with the same fin-flaring and pattern-intensifying that makes the species identifiable in the first place.
Breeding
Apistogramma lineata is a substrate-brooding cave spawner with maternal care, the standard reproductive mode for the genus. The female chooses a sheltered cavity — in the wild, a hollow under a leaf or among litter and rockwork; in the aquarium, a small cave, coconut shell, or the underside of a leaf — attaches her eggs to its ceiling, then tends and guards them while the male defends the wider territory. Clutch counts have not been formally published, but this is a very small fish and, in keeping with its closest relatives, lays small clutches; keepers who have bred it describe broods on the order of a few dozen fry rather than the larger spawns of bigger Apistogramma.
The one detailed first-hand account in circulation, from a keeper on Apistogramma.com, captures the species' quiet, undemonstrative breeding well. The female spawned so discreetly that the first sign was her leading a cloud of free-swimming fry out from under a leaf, never having shown the bright yellow brooding colours that betray most Apistogramma females. She proved a careful but nervous mother who kept her fry close, guarding successive broods at intervals of weeks rather than the near-continuous spawning of some congeners. The pinhead-sized fry took newly hatched brine shrimp once free-swimming, and the male stayed tolerant of them, consistent with the species' generally peaceable temperament.
Wild spawning has not been studied, but the breeding triggers are those of any upper-Orinoco blackwater Apistogramma: soft, warm, acidic water and the security of dense cover. Keepers report success at temperatures around 79–82 °F and recommend very low conductivity (under about 50 µS/cm). While wild fish live below pH 4.3, captive spawning is reported at considerably higher pH — around 5.5 — when the water is otherwise soft and clean.
In the aquarium
Apistogramma lineata is a genuinely uncommon fish in the hobby. It surfaces occasionally through specialist dealers and importers who work the upper Orinoco blackwater trade, but it is not a chain-store staple, and most aquarists who keep it have sourced it from breeders or targeted imports. Anyone who finds it should understand up front that this is a niche challenge, not a beginner's dwarf cichlid — its care requirements do not forgive shortcuts, and the fish is so small that mistakes read as disproportionately serious.
Tank: because males top out around 1 in standard length and females are smaller still, a pair or trio fits a relatively compact setup, but 15–20 US gal is a more workable minimum than the smallest tank that would physically hold them — this is a bottom-dwelling, territory-driven fish that needs floor space, not height. Use fine sand, dark for preference, with a generous covering of dried leaf litter (Indian almond, oak, beech, or similar) and at least one or two small caves or coconut-shell halves per female as potential spawning sites. Heavily planted sides and back give visual breaks that reduce stress and let the pair retreat from each other's sight between interactions. A tight-fitting lid is advisable; like many tiny Apistogramma they will jump.
Water: chemistry is where this species admits the least compromise. In the wild it lives in water as soft and acidic as any cichlid habitat on record — a field pH below 4.3 and conductivity around 12 µS/cm have been logged. Captive spawning has been achieved at much more moderate values (around pH 5.5) provided the water is genuinely very soft, so a practical target is pH 5.0–6.0, total hardness well under 5° dGH, and conductivity under 50 µS/cm. Aged reverse-osmosis water reconstituted with a small quantity of blackwater conditioner or peat extract is the standard approach; the tannin staining matters as much for the fish's sense of security as for the exact numbers. Temperature should sit in the mid-to-upper range of the wild figure — 79–84 °F is comfortable, with the lower end during cooler weather when no breeding stimulus is wanted. These are fish from a heavily shaded, warm blackwater creek and should never be kept in hard, alkaline tap water.
Tankmates: given the species' tiny size, only fish that clearly cannot eat it belong in the tank. Small, peaceful blackwater schoolers — pencilfish (Nannostomus spp.), hatchetfish, or small tetras such as Hyphessobrycon species from similar soft-acid habitats — work as dither fish that reassure the cichlids and coax them into display without competing for the same microhabitat. Avoid anything large or boisterous, and avoid other bottom-dwelling or shelter-occupying cichlids that would compete for the caves. Dwarf shrimp and other invertebrates are risky with any predatory cichlid, and especially with a species that forages micro-crustaceans from leaf litter in the wild — a breeding female will pick off anything small enough to swallow near her nest.
Breeding setup and common mistakes: for breeding, a harem of one male and two or three females works in a longer tank with enough visual separation that subordinate females can dodge the male's attention. Sexing is straightforward once the fish settle — males are larger, more vividly coloured, and carry extended dorsal and caudal fins; females are smaller and plainly coloured. The most common mistake is assuming that a female who has not turned bright yellow has not spawned. Unlike most Apistogramma, Apistogramma lineata females reportedly skip that conspicuous brooding signal, and the first sign of a successful spawn is often a female leading free-swimming fry out from under a leaf; keepers new to the genus who miss this and disturb the tank at the wrong moment can end a brood. Given the species' rarity in the trade and its Endangered status in the wild, anyone who keeps Apistogramma lineata and breeds it consistently is doing the hobby's captive stock a real service — this is not a species that can be easily restocked from wild imports if captive lines thin out.
Conservation
The IUCN Red List assesses Apistogramma lineata as Endangered (criterion B1ab(iii)), assessed on 24 July 2020 by Lina Mesa-Salazar — the species' own describer — and published in 2021. The listing reflects how restricted the fish is: criterion B1 is triggered by a very small extent of occurrence (under 5,0 mi²) combined with a severely fragmented or few-location distribution and a continuing decline in habitat quality. Apistogramma lineata is known only from a short reach of the río Atabapo and its immediate tributaries, so any degradation of that single stretch of blackwater bears directly on the whole species. Some hobby compilations, and the Cichlid Room Companion's species page, still describe the fish as 'not evaluated'; that is an out-of-date record, since FishBase and the Red List both now carry the 2020 Endangered assessment. The species is not listed by CITES.
That narrow range sits within a basin under real and growing pressure. The blackwater rivers of the upper Orinoco and Guainía — the Atabapo, Inírida, and Guaviare among them — drain a region where illegal alluvial gold mining has expanded sharply, bringing sedimentation that clouds these naturally clear-but-dark waters, mercury contamination, and riverbank disturbance, alongside deforestation of the flooded forest that supplies the leaf litter and tannins the ecosystem depends on. Apistogramma lineata is also collected for the ornamental trade, though as an uncommon, hard-to-find species the direct collection pressure appears modest. For a fish confined to one short blackwater river, the broader threat is plain: it has almost no geographic buffer, so basin-level disturbances that a wide-ranging Amazon cichlid could absorb are, for this species, potentially decisive. Its Endangered status should be read as a flag that habitat protection in the Atabapo, not collection limits alone, matters most for its future.