Taxonomy & naming
Farlowella amazonum was described by Albert Günther in 1864 in the Catalogue of the Fishes in the British Museum (volume 5, page 261), under the name Acestra amazonum, from specimens collected at Santarém, Pará State, on the lower Amazon. The combination Farlowella amazonum was established when the genus Farlowella Eigenmann & Eigenmann, 1889 was erected to accommodate these elongate twig-catfishes.
The species' synonymy is extensive. PlanetCatfish lists Acestra amazonum, Farlowella amazona, Farlowella carinata, Farlowella gladiolus, Farlowella oliveirae, Farlowella paranaense, Farlowella pleurotaenia, and Farlowella pseudogladiolus as synonyms; Farlowella platorynchus Retzer & Page, 1997, described from Peru and long circulated in the hobby under that name, is treated by FishBase as a synonym of F. amazonum pending final taxonomic resolution. The Catalog of Fishes (Eschmeyer, CAS) accepts F. amazonum (Günther, 1864) as the valid name. The species was redescribed by Retzer and Page in their 1997 revision of the genus in Proceedings of the Academy of Natural Sciences of Philadelphia.
Farlowella belongs to the tribe Harttiini of subfamily Loricariinae (Armbruster, 2004), a group characterised by the highly elongate, twig-like body and the distinctive rostrum (snout extension). With approximately 25 valid species, the genus is distributed across most of tropical South America.
Morphology
Farlowella amazonum is a spectacularly elongate fish reaching up to 9 in standard length (SL), with a total length including the attenuated caudal lobes that can approach 11 in — a body plan so extreme that the fish is essentially a swimming stick. The trunk is narrow, triangular in cross-section, and covered in keeled scutes; there are no paired lateral ridges projecting beyond the scute edges, distinguishing F. amazonum from some congeners. The rostrum — the prominent snout extension — is moderately long and slightly flattened dorsoventrally.
Coloration is cryptic brown to tan, with two prominent dark lateral stripes running from the tip of the rostrum through the eye to the caudal peduncle; these stripes closely simulate the dark edge-lines on a dry twig or reed stem. The ground colour may carry fine speckling or a reticulate pattern. The dorsal fin is positioned near the mid-body — a diagnostic feature of the genus distinguishing it from Sturisoma, in which the dorsal fin is placed conspicuously anterior.
Sexual dimorphism is pronounced. Mature males develop odontodes (small tooth-like dermal projections) on the snout, cheeks, and pectoral spines — most notably the interopercular odontodes, which become noticeably elongated during breeding condition. The male's snout odontodes give the rostrum a bristly texture visible at close range. Females are broader-bodied when gravid and have a smaller, rounder papilla compared with the pointed male papilla.
Habitat
Farlowella amazonum has a wide distribution: the Amazon basin from the lower Amazon (Santarém, type locality) through the Tocantins system, extending south to the La Plata drainage — a range spanning Brazil, Bolivia, and potentially adjacent countries. PlanetCatfish records distributions in the lower Amazon, upper Amazon, Tocantins, and La Plata drainages. This breadth, partly reflecting the historical lumping of multiple synonymous names under this species, means that ecological data come from a variety of localities and river types.
Typical habitat is shallow to moderately deep sections of clearwater or whitewater rivers and streams where dense marginal vegetation, submerged branches, and reed beds provide cover. The fish press themselves against submerged sticks, stems, and root surfaces in an orientation that makes them extremely difficult to detect; they are diurnal browsers in natural conditions. PlanetCatfish records temperature data of 73–81 °F, consistent with tropical lowland rivers throughout the range. pH is typically 5.5–7.5 depending on water type; conductivity varies widely across the broad geographic range, from soft clearwaters of the central Amazon to more mineralised La Plata tributaries.
Feeding
Farlowella amazonum is a periphyton and biofilm grazer, feeding primarily on the thin epilithic and epiphytic algal films that coat submerged wood, rocks, and plant stems. The oral disc is modified for fine-surface rasping; teeth are bicuspid and relatively delicate compared with the more robustly toothed Hypostomus. Gut-content analyses of Farlowella species consistently show high proportions of algae, diatoms, fine detritus, and sediment particles, with animal matter incidentally present. FishBase records a trophic level of 2.4 ± 0.2 se for the species, reflecting a minor omnivorous component above pure algal grazing.
In captivity, F. amazonum can be a challenging feeder to establish, particularly when imported as wild-caught adults. The fish requires abundant green algae growing naturally on glass, plants, and wood; a mature, well-lit, algae-coated aquarium is a prerequisite. Supplementary feeding with algae wafers, spirulina tablets, and — crucially — soft blanched vegetables placed to decompose slightly (courgette, cucumber, lettuce) is important. The PlanetCatfish Cat-eLog notes that twig catfishes should not be kept with 'aggressive or predatory fish' but do well with smaller tetras, hatchetfish, and Corydoras. Wood is grazed but not eaten in quantity; several pieces of driftwood provide both supplementary biofilm substrate and essential resting perches.
Mating
Courtship in Farlowella species has been described in aquarium observations of several congeners and is broadly similar across the genus. Males in breeding condition bear fully developed interopercular and snout odontodes and actively patrol surfaces in search of responsive females. A male locating a gravid female will orient alongside her, often pressing his body against hers, and follows her along plant stems and tank walls in a slow, parallel procession that can continue for hours before spawning commences.
The male's odontodes appear to play a role in stimulating the female through tactile contact along her flanks. Rival males will spar — pressing rostrum to rostrum and attempting to undercut each other with pectoral spines — but serious injuries are uncommon in well-structured aquaria with adequate space. Conditioned females are noticeably deeper-bodied and may show a slight pinkish hue around the ventral surface. PlanetCatfish notes recommended tank-mates as 'smaller Tetras or Rasboras' and specifically mentions hatchetfish as ideal due to their peaceful temperament; cichlids and larger catfish are to be avoided.
Breeding
Farlowella amazonum and its congeners have been bred in captivity, though PlanetCatfish records no registered breeding report specifically for this species as of mid-2026. Closely related species — particularly F. gracilis and F. vittata, which share the genus's egg-guarding spawning strategy — have been bred by hobbyists and provide the template for captive reproduction.
The male selects a flat, clean surface — typically the aquarium glass, a broad smooth stone, or a section of PVC pipe wall — and the female deposits a single layer of large, pale, adhesive eggs in a compact mass. Clutch sizes in Farlowella typically range from 40 to 100 eggs depending on female size and condition. The male then takes sole responsibility for guarding the clutch, fanning it constantly with his pectoral fins to maintain water movement and oxygen supply, and removing any dead or fungused eggs immediately. Incubation at 77–81 °F takes approximately seven to ten days. The male continues guarding after hatching until the fry disperse to graze independently. Rearing fry requires a biofilm-rich surface and either fine infusoria or commercial fry preparations; they are fragile in the first week and require very gentle filtration. Conditioning the adults on varied algae-based and vegetable-based foods, performing regular partial water changes, and slightly raising the temperature (to 81–82 °F) are the most commonly reported triggers for spawning.
In the aquarium
Farlowella amazonum represents a genus that consistently over-delivers on visual drama and consistently under-delivers on hardiness — at least in transit. Wild-caught specimens frequently arrive severely stressed and emaciated, making the post-import period critical. A quarantine tank with established algae growth, minimal water movement stress, and no competing fish is the best start. Once settled, the fish are surprisingly hardy and long-lived (five or more years in good conditions is well documented).
The minimum practical aquarium for a pair is 20–25 US gal, with ample length for the fish to cruise along glass surfaces — these are linear grazers, not corner-lurkers. Gentle to moderate current is important for oxygenation; the fish are found in well-oxygenated environments in nature. Temperature 73–81 °F; pH 6.0–7.5; soft to moderately hard water. The tank should be mature and algae-coated; a newly set-up aquarium with clean glass is insufficient to sustain the fish.
Farlowella are fragile in community settings with boisterous or nippy fish — danios, tiger barbs, and semi-aggressive cichlids will harass them mercilessly, particularly targeting the elongate fins and rostrum odontodes. Suitable company includes small, peaceful tetras (cardinal, rummy-nose, neon), pencilfish, hatchetfish, and small Corydoras. Multiple individuals can be kept together if space allows; the fish are not territorial outside of spawning periods. A pair or trio in a species or biotope aquarium yields the most rewarding observations.
The twig mimicry is fully expressed in a well-planted tank: the fish press themselves lengthways against stems or the glass at low angles, completely motionless for long periods, and are genuinely difficult to locate at a glance.
Conservation
The IUCN Red List assessed Farlowella amazonum as Least Concern in 2020, citing a broad distribution across the Amazon, Tocantins, and La Plata drainages, with no evidence of population-level decline. The species — or at least the name, which encompasses a complex of formerly separate taxa — is widespread across some of the largest and least-modified river systems on earth, including the central Amazon.
The more localised populations in the upper La Plata drainage and the Tocantins are exposed to greater anthropogenic pressure: deforestation of riparian vegetation that removes the overhanging stems and root mats the fish depend on, sedimentation from agricultural runoff that smothers the clean periphyton surfaces they graze, and hydroelectric impoundment on major Tocantins tributaries. The ornamental trade collects Farlowella species in moderate numbers from the Colombian and Peruvian Amazon, and mortality rates in transit and early captivity are high; any shift toward captive breeding of the genus would be ecologically and commercially beneficial. At present, however, no significant conservation concern has been identified for F. amazonum as a whole.