Taxonomy & naming
The German aquarist-ichthyologist Wolfgang Staeck described Apistogramma inornata in 2003, in the third volume of his Cichliden-Lexikon (Südamerikanische Zwergbuntbarsche), alongside a sister novelty from the same waters, Apistogramma velifera. The type locality is a pool at the entry of the Río Maniapure in Bolívar State, Venezuela, on the middle Orinoco. The holotype is held at the Museum für Tierkunde Dresden (MTD F 27042), with paratypes at Dresden (MTD F 27043, 27491–92) and further paratypes in Vienna's Naturhistorisches Museum; Zarske (2003) published the type catalogue. Regan coined the genus name in 1913 as a replacement for the preoccupied Heterogramma, joining Greek apistos, "inconstant" or "uncertain," to gramme, "line" — a nod to the variably developed, often incomplete lateral lines of these dwarf cichlids, reduced in many species to a scattering of pored scales. The epithet inornata is Latin for "unadorned" or "plain," chosen for the fish's inconspicuous colour. Within the genus, Apistogramma inornata belongs to the Apistogramma pertensis species-group — small, slim apistos with a naked anterior chest and, in males, dorsal-fin lappets drawn out well beyond the spine tips. A regional monograph by Mesa S. & Lasso (2011) for the Instituto Humboldt revised the genus across the Orinoco and placed Apistogramma inornata among the basin's striped-caudal forms; it remains valid and is the only member of its group restricted to that drainage.
Morphology
This is a genuinely diminutive fish. Examining Venezuelan material, Mesa S. & Lasso (2011) recorded specimens of 0.5–1 in standard length and diagnosed the species as a "dwarf" form that does not exceed about 1 in SL — among the smallest apistos known, and far below the 2.5–3 in reached by popular aquarium congeners (Staeck's original account gives a slightly larger size, so figures vary by sample). The body is elongate and laterally compressed, its dorsal and ventral profiles evenly curved, with a small triangular snout and roughly equal jaws. Colour is the species' defining trait precisely because there is so little of it: a plain brown ground crossed by about seven faint vertical bars, a single discrete lateral spot standing slightly proud of the longitudinal band, and — diagnostically — thick, straight, well-separated dark crossbars on the caudal fin. The first two or three dorsal rays are pigmented to the margin but never jet-black as in some relatives, and there is no bold abdominal striping — at most two indistinct abdominal stripes, against the three or four sharp dot-rows of the related Apistogramma velifera. As in other males of the pertensis group, the dorsal-fin lappets are drawn out beyond the spine tips. Sexual dimorphism follows the genus norm: males grow larger and carry the more developed, elongated finnage, females are smaller and rounder-bodied — though in a fish this plain the difference is correspondingly subtle. Meristically, Mesa S. & Lasso found 21–23 longitudinal scales, a dorsal count around XV–XVI with 6–7 soft rays, and the group's signature two (sometimes three) postlachrymal infraorbital pores.
Habitat
Apistogramma inornata is endemic to the Orinoco River basin of Venezuela; the Catalog of Fishes treats it as an Orinoco endemic, and FishBase records it only from that country. Its type locality lies on the middle Orinoco at the Río Maniapure (Bolívar), but most documented material comes from the lower Orinoco and the eastern Llanos: Mesa S. & Lasso (2011) map the species across the ríos Apure, Guárico, Uracoa, Guanipa, Morichal Largo, Upata, Imataca and Caura, and illustrate typical specimens from the "Llanos Orientales." These are warm lowland waters — the seasonally flooded savannas, blackwater palm-swamp creeks (morichales, fringed by Mauritia palms) and clear-water esteros that define the Llanos and the Guayana shield margins. Like its small congeners, it is a fish of leaf litter and shallow margins rather than open water; the documented habitats are shallow, on the order of 0–3 ft, with soft, acidic, tannin-stained water typical of the region. No published in-situ chemistry exists for Apistogramma inornata specifically, so the temperature and pH bands given here come from the regional Orinoco-Llanos envelope its congeners occupy rather than from measurements at its own collecting sites — a point worth flagging.
Feeding
No diet study has been published for Apistogramma inornata, so what can be said rests on the genus. Apistogramma are micro-predators of the substrate and leaf litter: they hover over the bottom and pick small benthic invertebrates — chironomid (midge) larvae and other aquatic insect larvae, microcrustaceans and similar meiofauna — often taking mouthfuls of fine sediment that they sift and expel through the gills. FishBase places the species at an estimated trophic level near 3.3, consistent with a small invertivore-omnivore. In a fish this tiny, the prey is correspondingly small: the bottom microfauna of warm, litter-floored blackwater. Its ecological role is that of one more diminutive predator near the base of the Llanos floodplain food web, itself prey for larger fishes, wading birds and aquatic invertebrates.
Mating
Reproductive behaviour has not been documented for Apistogramma inornata in the wild, nor in any detailed published account from captivity, so the pattern below is the well-established one of the genus, applied with that caveat. Apistogramma are cave-spawning dwarf cichlids: the female holds and defends a small breeding territory centred on a cavity — a crevice, a hollow under a leaf or root, an empty snail shell — while the larger male defends a broader area that may overlap several females, a loosely harem-polygynous arrangement. Courtship runs on colour and posture. A ripe female typically flushes a vivid yellow and performs flexing, bending displays to lure the male into her cave to fertilise the clutch. How fully this plays out in so small and plainly coloured a species — whose females cannot signal with the bright nuptial dress of, say, Apistogramma cacatuoides — is simply unrecorded, and worth being curious about rather than asserting.
Breeding
As with mating, the breeding biology of Apistogramma inornata has not been described, and the genus supplies the template. Apistogramma are maternal cave spawners: the female lays a small adhesive clutch on the roof or wall of her cavity — typically a few dozen eggs in small species, far below the hundreds of larger substrate-spawning cichlids — and tends them largely alone. She fans and guards the eggs, leads the wrigglers to pits, and shepherds the free-swimming fry in a tight school, flaring at intruders and flashing the fry back into cover at any threat, while the male patrols the wider territory. Larvae hatch in a few days and become free-swimming roughly a week after spawning, depending on temperature. For Apistogramma inornata specifically, the clutch size, fry development and any spawning triggers are undocumented; what is offered here is explicitly the genus-typical figure, not a measurement of this species, and the fish is rare enough in the hobby that reliable first-hand breeding reports are scarce.
In the aquarium
Apistogramma inornata is rarely seen in the hobby and is best described honestly as a specialist's fish rather than a beginner's one — not because it is technically demanding, but because it is genuinely scarce: very few importers handle it, and finding captive-bred stock takes patience and a foothold in dedicated apisto circles. Anyone who does obtain it is working with one of the smallest Apistogramma known, a fish under 1 in standard length, and the tank and tankmate choices follow from that as much as from its blackwater origins.
Tank: a fish this small is well served by a modest footprint. A 15–20 US gal tank (roughly a 60 × 12 in base) suits a pair or a small harem of one male to two or three females, provided the layout gives each female her own visual territory. Use fine sand — dark-toned river sand reproduces the Llanos leaf-litter floor and shows the fish to advantage. Dry leaves (Indian almond, beech, oak) laid thickly on the bottom are not decorative afterthoughts; they build the microhabitats, mild tannin staining and microfaunal layer the fish naturally exploits. Coconut caves, small clay pots on their sides, or bogwood with an enclosed hollow serve as spawning sites and female refuges. Keep filtration gentle — a small sponge filter at low turnover moves water without pushing a sub-2-cm fish around.
Water: chemistry is non-negotiable for a species from tannin-stained morichales. The facts for this article give 75–84 °F and pH 4.5–6.5; the soft, acidic end of that range (pH 5.0–6.0, conductivity under 100 µS/cm) best reflects the blackwater palm-swamp creeks it comes from, and conditioning fish to spawn in harder, more neutral water is not documented. Use reverse-osmosis water remineralised to very low hardness, or naturally soft, acidic source water, and keep a handful of leaves or a piece of driftwood in the tank for steady tannin input. For day-to-day maintenance, temperature can sit mid-range at 79–81 °F; a small seasonal drop and rise can serve as a spawning cue, as in many apistos, though that is genus-typical advice rather than something confirmed for this species.
Tankmates: because the fish is so small, choose companions carefully. Only peaceful, equally tiny fish make sense — small tetras of comparable size (neons and cardinals are the Orinoco classic, though even they can be boisterous next to a 2-cm apisto), pencilfish, or small Corydoras pygmaeus-group catfish work as dither fish and help the apistos feel secure enough to stay visible. Avoid anything large enough to treat the cichlids as food, and avoid other bottom-dwelling cavity-users that would compete for the limited cave real estate. A species-only setup with just the Apistogramma inornata colony is often the most productive route, and the one most likely to yield a breeding account.
Sexing and common mistakes: sexing is straightforward in principle — males are larger with more produced dorsal-fin lappets, females smaller and rounder — but the subdued colour makes it subtle in young fish; females in breeding condition show the genus-typical yellow flush. The usual soft-water dwarf-cichlid errors all apply: overcrowding females (each needs her own cave and room to escape the male when not receptive), using water that is too hard or too alkaline, and over-filtering with a current that disturbs the leaf-litter bed. Given how rarely this species is kept, any careful breeding record a hobbyist contributes to the specialist apisto community would be a real addition to what is known.
Conservation
The IUCN Red List assesses Apistogramma inornata as Least Concern (assessed 22 July 2020 by Lina Mesa-Salazar — the same specialist who co-authored the Orinoco revision of the genus — and published in 2020). It carries no CITES listing. As a small-bodied, non-commercial fish with no fishery value and only marginal presence in the ornamental trade, it faces no species-specific harvest pressure, and its occurrence across several Llanos drainages argues against an immediately narrow range. Even so, "Least Concern" here partly reflects how little is known: the species is rarely collected, its true distribution and population are poorly mapped, and a fish this small and localised is intrinsically harder to read than a widespread giant. The broader context is the Orinoco Llanos itself — a vast seasonal-flood system increasingly pressed by cattle ranching, agricultural expansion and water diversion, and by oil and mining activity across the Orinoco belt and the Guayana shield, all of which degrade exactly the shallow, blackwater morichal and savanna habitats this cichlid depends on. None is documented as a present threat to Apistogramma inornata, but they are the backdrop against which a small Llanos endemic's long-term security should be judged.