Taxonomy & naming
Synaptolaemus cingulatus was described by George S. Myers and Agustín Fernández-Yépez in 1950, placing it in the small genus Synaptolaemus within the family Anostomidae — the headstanders — in the order Characiformes. The genus name is diagnostic: Synaptolaemus fish have a distinctive fused or narrowly conjoined lower-lip structure adapted for scraping surfaces, setting them apart from the more numerous Leporinus and Anostomus headstanders in the same family.
The name's standing has since been questioned. A 2011 taxonomic review published in Zootaxa concluded that S. cingulatus is a junior synonym of Synaptolaemus latofasciatus (Steindachner, 1910) — itself originally described as a Leporinus — meaning the two names may refer to the same species, with latofasciatus having priority. Aquarium literature and the trade still use both names, sometimes for what may be colour-variant populations from different drainages (Ventuari-basin fish run more red, Xingu-basin fish more yellow), and this article follows the cingulatus name as requested while flagging that a keeper researching this fish should also check listings under S. latofasciatus.
Morphology
Synaptolaemus cingulatus has the classic anostomid headstander build: an elongated, laterally compressed, torpedo-like body with a small, terminal-to-slightly-underslung mouth set for grazing rather than grasping prey. The lower jaw carries the fused-lip structure that gives the genus its name, an adaptation for scraping algae and biofilm from wood and stone. Adults reach roughly 4–4.5 in, a modest size for the headstander group compared with the large, nippy Leporinus species.
Body colour is typically a silvery-to-golden base crossed by dark, often diagonal banding along the flanks — the "cingulatus" (banded) epithet describes this pattern — with the exact tone varying between populations. Fins are generally clear to lightly dusky. As in most headstanders, the fish swims and forages at a pronounced head-down, tail-up angle, a normal resting and feeding posture rather than a sign of distress.
Habitat
The species is native to South America, recorded from the upper Orinoco River, the Casiquiare canal that connects the Orinoco and Rio Negro systems, and the upper Xingu River basin in the Amazon drainage — a distribution spanning Venezuela, Colombia and Brazil. Aquarium-trade sourcing notes also place populations in the Rio Negro and Rio Tapajós.
It is a benthopelagic fish of tropical freshwater habitats, typically found around submerged wood, rocky substrate and current-swept margins where algae and biofilm accumulate — the surfaces it grazes. Water across this range is generally warm and soft to neutral; aquarium references give a workable range of roughly pH 5.0–7.5 and 68–82 °F, though the species is reported to need a warm minimum of around 75 °F to stay in good condition, consistent with its tropical, lowland Amazonian and Orinocan origins.
Feeding
Synaptolaemus cingulatus is an aufwuchs grazer — FishBase records a trophic level around 2.6, consistent with a herbivore/detritivore that spends its day rasping algae and biofilm from wood and stone rather than hunting. In the wild it works submerged driftwood and rocky substrate methodically, in the characteristic head-down posture, picking at the algal film and any small invertebrates caught in it.
In the aquarium it should get a vegetable-forward diet: algae wafers, blanched vegetables (courgette, spinach) and quality herbivore/omnivore pellets, supplemented with occasional small live or frozen foods. Driftwood itself is worth keeping in the tank not just for cover but as a genuine grazing surface, since the fish will work it the way it would work submerged wood in the Orinoco or Xingu.
Mating
Little is documented about courtship behaviour in Synaptolaemus cingulatus specifically. Aquarium sources note that it can show intraspecific aggression and is generally kept in groups, with males reported as smaller and more slender than females — the clearest sexing cue available, though not extensively documented in the literature. No distinct courtship display or pre-spawning ritual is described in the sources consulted; data is sparse for this aspect of the species' biology.
Breeding
As with most headstanders, Synaptolaemus cingulatus is understood to be an egg-scatterer, releasing eggs without building a nest or guarding a brood site — but it is rarely, if ever, bred in home aquaria, and no detailed spawning account is available in the sources consulted. Prospective breeders should treat this as effectively unbred in the hobby rather than expect a documented protocol; anyone attempting it would be working from the general egg-scattering pattern reported for related Leporinus and Anostomus headstanders rather than species-specific data.
In the aquarium
At a modest adult size of roughly 4–4.5 in, Synaptolaemus cingulatus is one of the more manageable headstanders to keep, but it still wants a tank on the order of 70 US gal or more, per hobby stocking guidance, generously furnished with driftwood and rocky hardscape to graze and current-swept open swimming space. Warm water is non-negotiable — sources put the minimum around 75 °F, with a broader workable range of roughly 68–82 °F and pH 5.0–7.5.
It shows intraspecific aggression and does best kept in a group rather than as a singleton, which also spreads out any squabbling. Unlike the notoriously nippy larger Leporinus and Anostomus headstanders, it is not flagged in the sources as a fin-nipper, but its grazing habit means it will happily browse soft aquarium plants along with algae and biofilm, so hardy, tougher-leaved plants or driftwood-anchored mosses are a safer bet than delicate stem plants. Because of the taxonomic overlap with S. latofasciatus, stock offered under either name should be treated as the same care profile.
Conservation
Synaptolaemus cingulatus has not been evaluated by the IUCN Red List, so no formal conservation status or population trend exists for it. It is a range-restricted species known mainly from the upper Orinoco, Casiquiare and upper Xingu systems, and FishBase characterises it as having high resilience and low vulnerability to fishing pressure, which is favourable, but the absence of assessment means real threats — habitat change, damming or the aquarium trade's collection pressure in these specific headwater systems — have not been formally quantified. The taxonomic uncertainty with S. latofasciatus also complicates any future assessment, since population data may need to be pooled or separated depending on how that question is resolved.