Taxonomy & naming
Farlowella smithi was described by Henry Weed Fowler in 1913 in a paper treating fishes from the Madeira River, Brazil, published in the Proceedings of the Academy of Natural Sciences of Philadelphia (volume 65, page 574, with figure). The type locality is the Madeira River, approximately 200 miles east of 62°20'W longitude, in Amazonas State, Brazil — coordinates best interpreted as the vicinity of the middle Madeira near Nova Olinda do Norte, with paratypes collected near Porto Velho.
The species was subsequently redescribed by Retzer and Page (1997) in a broader revision of Farlowella. The Catalog of Fishes (Eschmeyer, CAS) recognises Farlowella smithi Fowler, 1913 as the valid name. The genus Farlowella is placed in the subfamily Loricariinae and represents the most extremely elongate body form within that subfamily — superficially resembling a woody twig or stick, with the slender rostrum extending well forward of the eyes and the body tapering to a thread-like caudal region.
Morphology
Farlowella smithi reaches a maximum of 4 in standard length (SL). The body is extraordinarily slender throughout — one of the most attenuated body forms in Loricariidae. The snout (rostrum) projects conspicuously forward of the eyes, forming an elongate pointed structure that gives the genus its common name of 'twig catfish' or 'stick catfish'. The dorsal surface is keeled and covered in bony scutes; the ventral surface is partly plated.
Coloration is brownish overall, with two lateral dark stripes running from the rostrum tip through the eye and continuing along the flanks to the tail base — a consistent patterning feature across Farlowella. The dorsal fin is positioned near the body midpoint and is only slightly anterior to the anal fin. The caudal fin is small relative to body length.
Sexual dimorphism in Farlowella follows the genus-wide pattern: mature males develop conspicuous hypertrophied odontodes (bristle-like denticles) along the sides of the snout and rostrum. These 'cheek bristles' are absent in females and are the most reliable external sexing character. Gravid females may be subtly deeper-bodied when viewed from the side.
Habitat
Farlowella smithi is distributed through the middle Madeira River basin, including the Amazon, middle Amazon (Solimões), Madeira, and middle Madeira drainages (PlanetCatfish). The Madeira is the largest southern tributary of the Amazon and carries sediment-rich whitewater from Andean headwaters, but the middle reaches are influenced by a mix of clear-water and blackwater tributaries draining the Brazilian Shield, creating a complex mosaic of water types.
Twig catfishes in the genus Farlowella are strongly microhabitat-specific: they associate closely with submerged woody debris, aquatic plant stems, and the undersides of broad-leaved aquatic vegetation, where their cryptic body form renders them nearly invisible against the background. They graze the biofilm — the thin layer of algae, bacteria, and fine organic matter — that colonises these submerged surfaces. Water parameter data for F. smithi specifically are not available in FishBase or in published aquarium literature; general Madeira basin values include warm tropical temperatures and variable pH depending on tributary origin.
Feeding
Farlowella smithi is a biofilm and algae grazer. The ventral mouth is suited to rasping the thin layers of periphyton, diatoms, and associated organic material from smooth surfaces — submerged plant stems, leaves, driftwood, and aquarium glass are all used as grazing substrates. The trophic level of 2.6 (FishBase) confirms a diet low on the food chain, heavily plant- and algae-derived.
In an aquarium setting, twig catfishes require a steady supply of surface biofilm and algal growth, supplemented with algae wafers, blanched vegetables (courgette, cucumber, spinach), and spirulina-based foods. They are slow, methodical feeders that may be outcompeted at feeding time by faster or more aggressive bottom-dwellers. Protein-rich foods are generally not a significant part of the diet.
Mating
In Farlowella, mature males are recognisable by the developed rostral odontodes (cheek bristles) that appear during and after sexual maturity. These elaborate bristles play a role in male-male competition and are assessed by females during mate choice. Males typically select a smooth vertical or near-vertical surface — a broad plant leaf, the aquarium glass pane, a smooth piece of driftwood — as the spawning and egg-guarding site.
Specific courtship observations for F. smithi are absent from the published literature. By genus-level analogy, the male positions himself at the chosen substrate and the female deposits eggs directly onto the surface, where they adhere. No species-specific mating observations are recorded for F. smithi in either wild or aquarium settings.
Breeding
No breeding reports for Farlowella smithi are recorded in the hobby literature (PlanetCatfish). The wider genus Farlowella has been bred in aquaria, and the general pattern involves adhesive egg deposition on a smooth hard surface — often the aquarium glass — followed by paternal guarding. The male fans the egg mass with his pectoral fins and remains close, defending it from disturbance until the fry hatch and become free-swimming.
Farlowella fry are delicate and require very clean, well-oxygenated water with a reliable supply of biofilm on surfaces. Raising fry to juvenile stage in captivity demands careful attention to water quality and food availability. Given the absence of any breeding records for F. smithi specifically, extrapolation from congeners is the only available reference framework.
In the aquarium
Farlowella smithi is an infrequently kept species, overshadowed in the hobby by the more commonly encountered F. acus and related species. Its requirements are shared with the genus: clean, well-oxygenated water, a substrate and tank furniture rich in grazing surfaces (algae-colonised driftwood, broad-leaved plants such as Amazon swords or Anubias, and glass panels), and gentle tankmates that will not harass a slow-moving, delicate fish.
The species is peaceful and should not be kept with fin-nipping fish or boisterous mid-water species. PlanetCatfish notes compatibility with smaller tetras and rasboras, Corydoras, and other non-aggressive fish; larger cichlids or competitive catfish should be avoided. A tank of 20–30 US gal is appropriate for a pair or small group.
The absence of published water parameter data for F. smithi requires the aquarist to work from Madeira basin generalities: temperatures in the 75–82 °F range are reasonable, with near-neutral to slightly acidic pH appropriate for fish originating from a basin with significant blackwater-influenced tributaries. Strong filtration and regular partial water changes are essential — twig catfishes are sensitive to elevated nitrates.
Conservation
The IUCN Red List assessed Farlowella smithi as Least Concern, with the evaluation completed on 26 October 2020. The species is known from the middle Madeira River drainage, a large basin with extensive natural habitat, and no major documented threats are recorded in the assessment.
The Madeira basin has experienced significant hydroelectric development in recent decades, including the Jirau and Santo Antônio dams near Porto Velho — the vicinity of the paratypes of F. smithi. Dam construction alters flow regimes, sediment dynamics, and the structure of instream habitat on which twig catfishes depend, potentially affecting local populations. Broader distribution data across the middle Madeira would help assess whether such localised modifications represent a significant concern for the species as a whole. At present it is not considered threatened.