Taxonomy & naming
Apistogramma linkei was described in 1985 by the German cichlid specialist Ingo Koslowski, in a Bonner Zoologische Beiträge paper that introduced several new dwarf cichlids from the Río Mamoré system of Bolivia. The name has stood ever since — the Catalog of Fishes, FishBase and the IUCN all treat it as valid, with no junior synonyms. Koslowski worked from an unusually generous type series for a fish this small: the holotype (ZFMK 13323, in the Zoologisches Forschungsmuseum Alexander Koenig in Bonn) plus dozens of paratypes held across European and South American museums, all collected in 1983. The type locality lies northwest of Santa Cruz, Bolivia, at roughly 16°20'S, 68°25'W, in the upper Bolivian Amazon. Within Apistogramma — a genus of well over a hundred named species and many more undescribed forms — Apistogramma linkei belongs to the regani lineage. The specialist Mike Wise places it in the Apistogramma-commbrae complex, a cluster of mostly small, deep-bodied fishes centred on the Bolivian Amazon and the Río Paraguay system; their shared field mark, useful for this species, is the caudal blotch formed where the lateral stripe and the seventh vertical bar merge into a spot at the tail base. In the hobby the fish is sold consistently as 'Linke's dwarf cichlid', and should not be muddled with the 'Rotpunkt' or 'red-point' apisto — a separate Colombian fish, a form of Apistogramma cf. alacrina, that the trade names quite differently.
Morphology
This is a small fish even by Apistogramma standards. The checklist figures on FishBase, from Kullander's 2003 treatment, give a maximum of about 1.5 in standard length for males and 1.5 in for females. An older aquarium reference cites 2.5 in total length, but the scientific material does not bear that out; read it as the rare large male measured tip to tail. The body is the compact, moderately deep, laterally flattened shape typical of the commbrae-complex dwarfs. Ground colour runs soft tan to grey-brown over a pale belly, and mature males add blue-green iridescence on the cheeks and flanks with a warm orange or reddish wash in the unpaired fins. The most reliable marking is the caudal blotch at the tail base — the dark spot that gives the regani-lineage dwarfs their look — set off by a broken lateral band and faint vertical bars the fish can darken or wash out with mood. The sexes are easy to separate once mature: males grow larger, carry more colour, and develop longer, more pointed dorsal and anal fins, while females stay smaller and plainer and turn an intense yellow when guarding eggs. Because several Bolivian congeners share the basic pattern, confident identification leans on locality and on the exact shape of that caudal blotch.
Habitat
Apistogramma linkei lives in the upper Madeira drainage, on the southwestern rim of the Amazon basin. Its documented range runs through the Bolivian Amazon — the Mamoré, Beni and Madre de Dios systems — and crosses into Peru, where it has been recorded in Tambopata National Park; surveys also report it from the Manuripi and Nareuda rivers of Bolivia's Pando department. These are lowland but inland waters, sitting at roughly 150 to 250 metres elevation. The species avoids the open main rivers. It occupies ponds, oxbow lakes, seasonally flooded areas, small rivers and shaded forest streams — the quiet, leaf-littered margins where dwarf cichlids hunt and breed. The Mamoré–Iténez region carries a mix of clear and white water rather than the acidic blackwater of the Río Negro. A biotope reconstruction of a Mamoré forest stream near the Guaporé mouth, where Apistogramma linkei lives alongside Mikrogeophagus altispinosus, records roughly 70–82 °F, pH about 6.6–7.2 and low conductivity around 110–220 µS/cm, the water faintly tea-stained from leaf litter; FishBase lists an aquarium temperature preference of 75–79 °F. The substrate is sand strewn with drowned leaves, fine twigs and wood — the cover this cave-spawner depends on. No precise depth survey exists, so we give a nominal 0–3 ft: like other shallow-stream and pool apistogrammas, it keeps to the top metre of water.
Feeding
Like its relatives, Apistogramma linkei is a micro-predator of the leaf litter and soft sediment. The IUCN assessment sums up its diet as based mainly on aquatic arthropods, which fits the genus's general ecology: these dwarfs work the bottom and litter layer for insect larvae, small crustaceans, microcrustaceans and other tiny invertebrates, sieving mouthfuls of sand and detritus to sort out what is edible. FishBase places the fish around trophic level 3.3 — a carnivore-leaning omnivore rather than a plant feeder. In its forest-stream and floodplain habitats it fills the small-invertivore niche at the base of the fish community, and is itself prey for larger cichlids, characins and birds. No gut-content study specific to Apistogramma linkei has been published, so the dietary picture comes from the IUCN note and from the well-documented feeding of the genus as a whole.
Mating
Apistogramma linkei runs on the polygynous harem that defines much of the genus. A dominant male holds a comparatively large territory that overlaps the smaller territories of several females, each guarding a cave or sheltered crevice. Pairing is female-driven within that structure: a ripe female colours up, claims her cave, and courts the male into spawning, after which she does the close work of egg care while he patrols the perimeter and turns back rivals. FishBase captures the male's role well — he is 'very secretive about the eggs', there for defence and the occasional quiet visit rather than constant attendance at the nest. Because of this division of labour, one male can father several simultaneous clutches across his harem. Aggression is real but scaled to the fish: disputes are mostly display and chasing, and the main practical hazard in a tank is a male harassing an unready female, or females turning on each other when caves are too few.
Breeding
Apistogramma linkei is a cave-spawning harem breeder. The female picks a small enclosed cavity — under wood or a leaf, in a crevice, or in the tank a flowerpot or coconut shell — and fixes her eggs to its ceiling in the characteristic Apistogramma posture. She tends and fans the clutch in near-darkness while the male guards the surrounding ground; FishBase records the female as the clutch-tender and notes that the male often shares in caring for eggs and larvae. Once the eggs hatch she leads the wrigglers, and later the free-swimming brood, in a tight defended cloud around the cave, herding them back to cover at any threat. No wild clutch count is published for Apistogramma linkei; harem-spawning Apistogramma of this size typically lay on the order of a few dozen to a hundred-plus eggs per spawn, and that genus-typical range is the best guide here. The fish has a long, forgiving reputation in the hobby — a 1980s German account titled it 'a dwarf cichlid without breeding problems' — and keepers find the standard triggers work: soft, slightly acidic water, a temperature in the mid-20s °C, plenty of caves, and small live and frozen foods to bring females into condition.
In the aquarium
Few apistos are as beginner-friendly, largely because Apistogramma linkei tolerates a wider range of chemistry than its fussier Bolivian and Colombian relatives; it does not demand the very soft, acidic water the exacting species require. What matters most is clean water and a well-planned floor.
Water: pH 6.6–7.2 and moderate hardness suit it, at 72–82 °F — about 77 °F serves both daily keeping and spawning. Regular partial water changes matter more than chasing exact numbers; clean, well-oxygenated water keeps the colour up and the females willing to spawn.
Tank: one male with two or three females fits a 23.5–31.5 in tank of roughly 15–20 US gal, with more room welcome for extra females. Floor space beats height, since the fish stays near the bottom of shallow water. Lay down fine sand, dried leaves (Indian almond or beech), driftwood and rounded stones under gentle flow and moderate light — strong current and bright overhead lighting both send it into hiding. Provide at least one cave per female: half-coconut shells, unglazed flowerpots on their side or small terracotta tubes all serve. Java fern, Anubias on wood and floating plants are welcome but optional.
Tankmates: small open-water dither fish — ember or rummy-nose tetras and similar soft-water characins — settle the females and draw them out. Avoid large, boisterous or nippy fish; even peaceful bigger cichlids leave the male anxious and the females cryptic. Small Corydoras generally mix well, provided they do not monopolise the cave entrances.
Common mistakes: the usual failures are too few caves, or females crowded with no visual breaks between territories, which brings constant fighting and reluctant spawning — each female needs her own cave and a defendable patch of ground. And because juveniles are hard to sex in the shop, a 'pair' often turns out to be two males or two females; buy a small group of several-month-old fish and let them sort themselves out. Newly free-swimming fry take micro-foods at once — infusoria, commercial fry powder and baby brine shrimp — and rear without much fuss, the fish spawning again readily in good conditions.
Conservation
The IUCN Red List assesses Apistogramma linkei as Least Concern (assessed 23 April 2014 by J. Sarmiento and M. Maldonado, published 2016). The reasoning is straightforward: the fish is widely distributed across the Bolivian Amazon and into Peru, appears common, and occurs in at least one protected area, Tambopata National Park. Its population trend is listed as unknown but not declining, and it carries no CITES listing. The assessment does flag the pressures that bear on a small floodplain fish — habitat modification and pollution from agriculture and livestock ranching, which degrade the shallow streams and pools it needs. It is not a food fish, and the trade in it is modest; the IUCN notes only its potential as an ornamental, and its low fishing-vulnerability score reflects that. The wider backdrop is the upper Madeira basin, where the Mamoré and Beni and their floodplains face plastic pollution, agricultural runoff and the cumulative effects of land-use change along their banks — diffuse pressures rather than a single acute threat. For now those weigh only lightly on a habitat generalist like Apistogramma linkei, but they are the backdrop against which a fish this dependent on intact marginal habitat should be watched. The assessment itself is now more than a decade old, and the Red List flags it as needing an update.