Amazon basin

The chocolate talking catfish, Acanthodoras cataphractus, is a doradid catfish from the northern Amazon basin and Atlantic drainages of the Guianas. It is most often exported as bycatch among Platydoras armatulus and is sold under the same trade names as A. spinosissimus, which has pale blotches on the back between the dorsal and caudal fins where this species has pale lines or no markings. Largely nocturnal and gregarious, it is best kept in a group of at least four.

The chocolate talking catfish, Acanthodoras spinosissimus, is a doradid catfish from the northern Amazon basin and the Essequibo in Guyana. Usually exported as bycatch among Platydoras armatulus, it is sold under the same trade names as A. cataphractus, and the most useful difference is the pale blotches on its back between the dorsal and caudal fins. Largely nocturnal and gregarious, it is best kept in a group of at least four.

The red barracuda tetra, Acestrorhynchus altus, is a predatory acestrorhynchid that may be restricted to the lower Amazon in Brazil. A member of the A. lacustris group, it has a round humeral spot and is virtually impossible to tell from its relatives in the trade unless collection data is known. An obligate piscivore of open water, it is best kept in a group of four or more of comparable size, since acestrorhynchids are cannibalistic.

The red-tailed freshwater barracuda, Acestrorhynchus falcatus, is a predatory acestrorhynchid from the northern Amazon and Orinoco basins. It also occurs in coastal rivers of Guyana, Suriname and French Guiana. Its large humeral spot, shaped like an inverted tear drop, separates it from other Acestrorhynchus. Reaching 250 to 275 mm, it needs plenty of open water, and a group must be of comparable size because acestrorhynchids are cannibalistic.

The big-eyed cachorro, Acestrorhynchus falcirostris, is a large predatory acestrorhynchid from northern Amazon drainages and the Orinoco. The two dark body stripes of the A. nasutus group appear only in its juveniles, and at 320 to 350 mm SL it grows far larger than the other members. A black fringe to the rear of the operculum gives it a 'collared' look. It needs open water, and a group must be of comparable size because acestrorhynchids are cannibalistic.

The striped barracuda tetra, Acestrorhynchus isalineae, is a small predatory acestrorhynchid from the rio Madeira basin in the Brazilian Amazon. Most records come from the type locality, a tributary of the rio dos Marmelos. Like others in the A. nasutus group it keeps two dark longitudinal stripes into adulthood and stays around 100 mm. Acestrorhynchids are cannibalistic given the opportunity, so a group must be of comparable size.

The pike tetra, Acestrorhynchus microlepis, is a predatory acestrorhynchid from northern Amazon drainages and the Orinoco. It also occurs in coastal rivers of Guyana, Suriname and French Guiana. A member of the A. microlepis group, it has a small blackish spot behind the gill cover and is separable from the very similar A. grandoculis only by counts. It tends to take smaller prey such as tetras, and acestrorhynchids are cannibalistic, so a group must be of comparable size.

The Pantanal barracuda tetra, Acestrorhynchus pantaneiro, is a predatory acestrorhynchid from the Paraná, Uruguay and de la Plata basins. It also occurs in the rio Mamoré in Bolivia. A member of the A. lacustris group with a round humeral spot, it is virtually impossible to tell from its relatives in the trade unless collection data is known. It lives in open water, and a group must be of comparable size because acestrorhynchids are cannibalistic.

The sheep pacu, Acnodon normani, is a serrasalmid from Brazil, possibly restricted to the Xingu and Tocantins watersheds of the Amazon basin. Also known in the trade as 'tiger pacu', it is often said to be a frugivore or herbivore, but aquarium observations suggest it also feeds on the scales of other fishes. That makes it unsuitable for the community aquarium, although it does not seem to target much smaller species.

The spotted talking catfish, Agamyxis pectinifrons, is a doradid catfish from the Amazon basin in Bolivia, Brazil, Colombia and Peru. Very common in the trade, it is hardy and relatively long-lived, and recommended to beginners and experienced aquarists alike despite its adult size. It closely resembles A. albomaculatus, known only from the Río Orinoco drainage in Venezuela, and the two are probably sold under the same trade names.

The manduba, Ageneiosus inermis, is a large auchenipterid catfish found throughout much of South America east of the Andes. At around 470 mm SL it would need an aquarium in excess of 400 x 120 cm as an adult and is largely unsuitable for private aquaria. An obligate carnivore, it can take surprisingly large prey, and the larger Ageneiosus species are often used as food fishes in their native countries.

The duck catfish, Ageneiosus ucayalensis, is an auchenipterid catfish described from Peru and recorded across the Amazon, Orinoco and Guianas. Body patterning apparently varies with locality, and fish from black water habitats, particularly on the Guiana Shield, tend to be darker. Growing to around 290 mm SL and capable of taking large prey, it is safe only with similarly sized catfishes or large pelagic characins, mostly a combination for public aquaria.

The marbled talking catfish, Amblydoras nauticus, is a small doradid catfish from Peru, described from Nauta in the Peruvian Amazon. It is often still sold as A. hancockii, a name now considered a synonym of Platydoras hancockii. Hardy and tolerant of a wide range of water conditions, it is secretive and rarely seen by day. It makes audible sounds by grinding its pectoral spines in their sockets and by resonating the swim bladder, and its spines tangle easily in nets.

Ancistrus dolichopterus, the starlight ancistrus (L183), is a bristlenose catfish most likely endemic to the middle and lower rio Negro, Brazil. It inhabits blackwater streams. The name has been used for the common bristlenose and other similar species, while this fish has been called A. hoplogenys, and much of the literature confuses them. It differs from all congeners in having 9 soft dorsal-fin rays, and is territorial with conspecifics and similarly-shaped species.

Ancistrus ranunculus, the medusa pleco (L034), is a wide-headed, flattened suckermouth catfish from the rio Xingu and rio Tocantins basins in Brazil. It lives among rocks in shallow, fast-flowing water, needs well-oxygenated water with plenty of movement and a protein-rich diet, and is often in poor condition after import. Juveniles carry light spots like the similarly shaped L255, but in A. ranunculus these fade as the fish matures.

L255, the spotted medusa plec, is a wide-headed, flattened Ancistrus known only from the middle rio Xingu basin in Pará state, Brazil. It lives among rocks in shallow, fast-flowing water, needs well-oxygenated water with plenty of movement and a protein-rich diet, and is often in poor condition after import. It resembles A. ranunculus, but keeps its light body markings throughout life, whereas those of A. ranunculus fade as the fish matures.

The striped headstander, Anostomus anostomus, is an anostomid from the Amazon and Orinoco river systems in Peru, Brazil, Venezuela and Guyana. It lives along rocky shores of fast-flowing rivers, grazing algae and small invertebrates from the rocks. Although it shoals in nature, it is very quarrelsome with conspecifics when only a few are kept, so it is best kept singly or in a group of 6 or more in a larger tank.

Apistogramma agassizii is a dwarf cichlid found through much of the Amazon/Solimões basin, from the Río Ucayali in Peru to the Capim River in Brazil. Colour and pattern vary considerably with locality, and numerous ornamental forms have been selectively bred for the trade. It inhabits slower-moving tributaries and creeks where leaf litter collects. Captive-raised fish suit the community aquarium, while wild fish are best kept alone or with small dither fishes.

The redspot dwarf cichlid, Apistogramma alacrina, is from the Río Guaviare (Orinoco) and Río Orteguaza (Amazon) drainages in Colombia. It differs from all other described members of the genus in having dark blotches at the dorsal and ventral base of the pectoral fins. Three very similar fishes coded A106, A107 and A108 may or may not be conspecific with it, since they show some differences in colour pattern and morphology.

The Inca dwarf cichlid, Apistogramma baenschi, is from tributaries of the lower Río Huallaga in the Amazonian portion of northern Peru. Coded A188 under the DATZ system, it is produced on a commercial basis and is perhaps among the most suitable Apistogramma for those new to dwarf cichlids. Wild fish come from shallow forest tributaries with very soft, tea-stained water and a pH measured between 4.1 and 6.3.

The two-striped dwarf cichlid, Apistogramma bitaeniata, ranges across the Peruvian, Colombian and Brazilian Amazon, from the Marañón to the Tapajós. Also known as the banded dwarf cichlid, it occurs in several colour forms depending on locality, loosely grouped as 'red', 'blue', 'orange' and 'yellow' in the hobby. Many locality names are in use for these forms, and several are regularly applied incorrectly.

Borelli's dwarf cichlid, Apistogramma borellii, is from southern Brazil, Paraguay, Argentina and Uruguay. Also known as the umbrella or yellow dwarf cichlid, it occurs in creeks and tributaries of the rio Paraguay, lower rio Paraná and Uruguay systems. Captive-raised fish are the recommended choice for the community aquarium, while wild examples are best kept alone or with small dither fishes.

Apistogramma brevis is a dwarf cichlid from the Rio Uaupés basin in far northwestern Brazil and the Rio Tiquié in southern Colombia. It has also been recorded in the upper Rio Negro and Rio Orinoco, and inhabits slow-moving blackwater streams where the pH can drop as low as 4.0 or 5.0. Coded A168, it is the type species of the A. brevis group, and breeding is not too difficult if very soft, acidic water can be provided.

The cockatoo cichlid, Apistogramma cacatuoides, is a small cichlid from the upper Amazon basin, from the Ucayali in Peru to the Solimões in Brazil. It lives in slow tributaries, backwaters and creeks where leaf litter collects. Numerous line-bred forms such as 'double red' and 'orange flash' are traded, and captive-raised fish suit a community aquarium, while wild fish are best kept alone or with small dither fishes.

Apistogramma elizabethae is a dwarf cichlid from the rio Uaupés and adjacent rio Içana, both tributaries of the upper rio Negro in Brazil. Coded A208, it is among the more sought-after Apistogramma in the hobby. Içana fish tend to have more blue on the head than those from the Uaupés, a reddish population is traded as A. elizabethae 'super red', and none of the forms should be mixed in aquaria.

Apistogramma eremnopyge (A218) is a dwarf cichlid known only from Loreto region in northeastern Peru, in the Itaya, Nanay and Tapiche drainages. Traded under names including A. sp. 'strawberry', 'red beard' and 'diamante', it has a dark blotch low on the caudal peduncle in both sexes. Pairs can apparently be kept only when other pairs are visible in adjacent tanks, so a group of several males with more females is preferable.

Apistogramma eunotus is a dwarf cichlid from the Río Ucayali in Peru and the Solimões/Amazon in Colombia and Brazil, as far east as the Japurá. Coded A73 under the DATZ system, it has similar-looking, possibly conspecific populations referred to as A74 to A77 depending on locality. It inhabits slow-moving streams, creeks and tributaries, and captive-raised fish are the recommended choice for the community aquarium.

The blackline apisto, Apistogramma gibbiceps, is a dwarf cichlid from the Rio Branco and middle Rio Negro basins in Brazil. It is identified by a row of short dark marks low on the flank below the lateral band, which show most clearly on a settled fish. Meinken's type series held three species, and A. roraimae from the Rio Branco has been treated as a synonym since 2003.

Apistogramma paulmuelleri (A52) is a dwarf cichlid apparently endemic to Loreto, Peru, described from a forest stream near the Iquitos to Nauta road. It has been traded as A. sp. 'Apache', a name also applied to other, non-conspecific Apistogramma. Since 2009 parts of the type locality stream have been degraded by removal of riparian vegetation.

Apistogramma sp. 'breitbinden' is an undescribed dwarf cichlid from the upper Rio Negro in Brazil, the Venezuelan Orinoco and the Inirida in Colombia. The German name means 'broad-banded' and refers to the uniformly broad suborbital stripe of males. Known in the hobby for several decades, it is often imported as bycatch among shipments of wild-collected A. iniridae, and some populations carry the DATZ codes A164, A165 and A167.

The gulper catfish, Asterophysus batrachus, is a predatory auchenipterid catfish from the rio Negro in Brazil and the Orinoco in Venezuela. Also called the 'ogre catfish', it hunts in shallow blackwater tributaries, mostly at night. It can consume fishes almost twice its own size and is not recommended for the community aquarium.

The oscar, Astronotus ocellatus, is a large cichlid widely distributed in the Amazon region, recorded from Colombia and Venezuela south to Argentina. It grows to 350 mm SL and typically lives 10 to 20 years, both of which need taking into account before purchase. Most fish on sale come from commercial breeders in Eastern Europe or the Far East, in numerous ornamental strains, and genetic analyses suggest the genus contains additional, morphologically cryptic species.

The two spot astyanax, Astyanax bimaculatus, is a characid ranging from Panama through most of the Amazon and Orinoco basins. It lives in a wide variety of biotopes, from swiftly-flowing rivers and streams to ponds, ditches and reservoirs. The name is currently applied to what is considered a species complex of at least four taxa, and aquarium fish most often arrive as contaminants among shipments of other species.

Kennedy's tetra, Astyanax kennedyi, is a small characid endemic to the upper Amazon basin in Peru, around the city of Iquitos. Like most Astyanax it is rarely offered for sale, and the occasional specimen turns up mixed among shipments of wild fishes from Peru.

The midnight catfish, Auchenipterichthys coracoideus, is an auchenipterid catfish from the Peruvian and Brazilian Amazon and the Essequibo drainage. Also known as the 'Zamora woodcat', it has often been misidentified as A. thoracatus, and the two differ principally in anal-fin ray count. By day it shelters among submerged roots, tree stumps or vegetation in turbid rivers and flooded areas, emerging to feed in open water at night.

Balroglanis macracanthus is a small driftwood catfish endemic to the upper rio Negro system in Brazil. Poorly known but occasionally available in the aquarium hobby, it shelters among submerged wood by day and forages at night. Like other auchenipterids it practises internal insemination, and females can carry eggs and sperm packets until conditions trigger fertilisation.

The mango pleco, Baryancistrus chrysolomus, traded as L047, is a loricariid endemic to the rio Xingu basin in Pará state, Brazil. A broad, usually yellowish band along the edges of the dorsal and caudal fins throughout life separates it from B. xanthellus, whose bands shrink to tips in adults. It grows to around 220 mm SL, and males in particular become highly intolerant of conspecifics as they age.

The big white spot pleco, Baryancistrus sp. L142, is an undescribed suckermouth catfish from the rio Tapajós in Pará state, Brazil. It appears restricted to a short stretch of the river between Itaituba and Pimenta, in shallow, fast-flowing, warm water. The species is also traded as 'snowball pleco', a name first applied to Hypancistrus inspector and now used for several similar white- or yellow-spotted fishes. Males become highly intolerant of conspecifics as they age.

The gold nugget pleco, Baryancistrus xanthellus, is a suckermouth catfish endemic to the rio Xingu basin in Pará state, Brazil. It lives in whitewater rapids in the Volta Grande do rio Xingu, between Belo Monte falls and the mouth of the rio Iriri. Before its description it was traded as L018, L085, L177 and LDA060, and L081 is the same fish. Males become highly intolerant of conspecifics as they age.

The cupid cichlid, Biotodoma cupido, is a geophagine cichlid from much of the Amazon basin, north to the Essequibo in Guyana and south to Bolivia. Also traded as the 'green-streaked eartheater', it varies in colour pattern and shape by locality, and most traded fish come from around Santarém in Pará state. Unless breeding it is surprisingly peaceful. Its relatively compact body and a dark flank blotch above the upper lateral line separate it from B. wavrini.

The Orinoco eartheater, Biotodoma wavrini, is a geophagine cichlid from the Orinoco and rio Negro basins of Venezuela, Colombia and Brazil. One natural habitat is the Río Cinaruco, a low-nutrient blackwater tributary of the Orinoco. It can be told from B. cupido by its noticeably elongate body and a dark flank blotch on or below the upper lateral line. Unless breeding it is surprisingly peaceful, and trade populations include 'Cuao', 'Orinoco', 'San Antonio' and 'Sipapo Ventuari'.

Biotoecus opercularis is a small geophagine cichlid from the middle Amazon basin in Brazil, including the lower Madeira, Tapajós and Negro. It favours shallow, slow-flowing water over sand with leaf litter and submerged wood, often stained with tannins. Several populations are traded, among them B. sp. 'rio Negro' from the rio Jauaperi and B. sp. 'Santarém' or 'Tapajós', though no scientific evidence shows them to be more than one species. It should not be mixed with other Biotoecus species or populations.

The striped pike 'characin', Boulengerella lateristriga, is a ctenoluciid from the rio Negro basin and parts of the upper Río Orinoco. It appears limited to black water rivers and tributaries, where the water is stained darkly with humic acids and the pH can be as low as 3.0 or 4.0. A thin dark stripe from the rear of the eye to the caudal peduncle and dark crossbars on the caudal-fin lobes separate it from the similar B. maculata. It grows to 258 mm SL.

Boulengerella maculata is a pelagic ctenoluciid found throughout much of the Amazon, Orinoco and Tocantins river systems. Colour pattern varies considerably, with some specimens much paler than others, and this may be correlated with water type. Random dark spots on the upper body, and a dark stripe only behind the eye when one is present, separate it from the similar B. lateristriga. It reaches 329 mm SL and needs an aquarium with base dimensions of 240 by 90 cm or more.

The zebra shovelnose, Brachyplatystoma tigrinum, is a pimelodid catfish from the upper Amazon basin in Brazil, Colombia and Peru. Adults appear to be obligate inhabitants of main river channels with strong flow, often around cataracts and rapids, and most aquarium fish are juveniles collected around Iquitos in Peru. It is sometimes confused with B. juruense, especially when young, but has a more well-defined colour pattern, a slenderer body and longer barbels.

The false adolfoi, Brachyrhamdia rambarrani, is a heptapterid catfish from the Rio Unini, a blackwater tributary of the lower rio Negro in Brazil. It occurs with, and mimics, Hoplisoma davidsandsi, sharing its basic colour pattern, while the common name comes from its resemblance to H. adolfoi. Rarely seen in the trade, it tends to turn up as a contaminant among shipments of other species.

The imitator cory, Brochis imitator, long known as Corydoras imitator, is an armoured catfish endemic to the upper rio Negro basin in northern Brazil and southern Venezuela. It is one of several rio Negro congeners with an oblique dark bar along the dorsal surface of the body, a group that includes Hoplisoma adolfoi, H. burgessi and H. duplicareum. It inhabits pristine blackwater tributaries and flooded forest with tea-coloured water, very little hardness and a pH of 4.0-6.0.

Brochis incolicana (C001), long known as Corydoras incolicana, is an armoured catfish from the rio Içana in the upper rio Negro basin, northern Brazil. It presumably also occurs in eastern Colombia, where the Içana forms the border. The first fish to receive a 'C' number, in 1993, it was described the same year in a hobbyist magazine and is difficult to identify accurately. The colour pattern is said to be extremely variable, but the dark bar through the eye and the dark marking at the dorsal-fin base are apparently consistent.

Brochis lamberti (C009), long known as Corydoras lamberti, is an armoured catfish known only from the lower Río Pastaza, a tributary of the Río Marañón in Loreto, northern Peru. Similar-looking fish are known from tributaries close to Iquitos, and it is unclear whether these, 'C009' and B. lamberti are the same species. It is rare in the hobby and difficult to identify without collection details, so it may have been traded under other names.

The leopard cory, Brochis leopardus, long known as Corydoras leopardus, is a spotted armoured catfish from the western Amazon basin in Peru, Ecuador, Bolivia and Brazil. It looks very like Hoplisoma julii and H. trilineatum, but has a longer, more pointed snout and grows larger. Dias et al. (2024) moved it to the genus Brochis and put the two lookalikes in Hoplisoma, so the resemblance does not reflect a close relationship. The type specimens were aquarium imports.

Known in the hobby as the hognose 'Brochis', Brochis multiradiata, long known as Corydoras multiradiatus, is an armoured catfish from the northwestern Amazon basin in Ecuador and Peru. Formerly placed in Brochis, it has an extended snout and 17-18 dorsal-fin rays, against 6-8 in other Corydoras. Little is known of its habitat, but it is likely to live in smaller tributaries and still waters such as backwaters and oxbows, as closely related species do.

The blackwing hatchetfish, Carnegiella marthae, is a small freshwater hatchetfish from the upper Orinoco in Venezuela and the rio Negro in Brazil. It appears to be a stenotypic inhabitant of blackwater, found in igapó and igarapé habitats with overhanging vegetation and leaf litter. Very peaceful but small and timid, it is best kept in a group of 10 or more with similarly sized, peaceful fishes.

The pygmy hatchetfish, Carnegiella myersi, is a tiny freshwater hatchetfish from the Peruvian Amazon basin, with a second population in Bolivia. The smallest and most delicate of the nominal hatchetfishes, it has a shallower, rounded keel that gives it an elongate profile. It lives in small, shaded, shallow forest streams and must be kept in a group of at least six, away from active tankmates.

The marbled hatchetfish, Carnegiella strigata, is a hatchetfish from the Amazon and Orinoco basins and coastal rivers of Guyana and Suriname. Popular in the hobby, it is collected for the trade mostly in the rio Negro basin in Brazil. Its larger size and dark, marbled pattern set it apart from congeners, though the pattern varies and the wide range may be open to question. It appears to live only in blackwater.

The reticulated driftwood catfish, Centromochlus reticulatus, is a small auchenipterid first known from the upper Rupununi River basin in Guyana. Its secretive, mostly nocturnal habits mean it may have been overlooked elsewhere, and it has been recorded from the rio Preto da Eva near Manaus, Brazil. Sometimes traded as 'purple oil catfish', it is highly gregarious and ideally kept in groups of at least eight.

The spotted headstander, Chilodus punctatus, is a headstander from much of the Amazon, the western Orinoco and coastal rivers of Guyana and Suriname. Also called the 'checkered headstander', it lives in slow-moving rivers, oxbows and floodplain lakes, and its colour pattern appears to vary with locality. Shy and peaceful, it is sensitive to dissolved organic wastes and should never be introduced to a biologically-immature aquarium.

The Amazon puffer, Colomesus asellus, is a freshwater puffer found throughout much of the Amazon basin, with records north to Guyana and Venezuela. Also traded as the South American puffer or 'SAP', it is told from congeners by a transverse row of dermal flaps across the chin. It lives mostly in well-oxygenated river habitats, is intolerant of organic waste, and forms loose aggregations, so a group of 6 or more is best, away from the general community.

The red-spotted tetra, Copeina guttata, is a lebiasinid from the middle and upper Amazon basin in Brazil, Peru, Ecuador and Colombia. Reaching 76 mm, it needs a tank of at least 120 x 30 cm. The eggs are apparently deposited in a shallow depression dug in the substrate and guarded by the male. Like many fishes from pristine environments it is intolerant of organic pollutants and requires spotless water.

Copella callolepis is a small lebiasinid from the central Amazon region of Brazil, where all recent records come from. It is quite common in the aquarium trade but normally misidentified as C. nattereri or the very similar C. meinkeni. It lacks the dark lateral stripe of C. nattereri, and differs from C. meinkeni in a black triangular marking in the lower caudal-fin lobe and blue-black to dark brownish-red spots.

The spotted splashing tetra, Copella meinkeni, is a small lebiasinid from the central Amazon region, with most records from the rio Negro and Orinoco. It has been widely referred to as C. nattereri in aquarium literature, but lacks that species' dark lateral stripe and has 5-6 rows of bright red spots on the body. The similar C. callolepis is also traded. It inhabits forest streams with tea-coloured water and lays its eggs among vegetation.

Copella nattereri is a small lebiasinid widespread in the middle and upper Amazon drainage in Peru and Brazil. It is sometimes traded as C. sp. 'red line', 'spotted tetra' or C. nigrofasciata, and its name was long applied to C. callolepis and C. meinkeni. Of the three it alone has a dark lateral stripe, and it has no more than three rows of red spots on the flanks. It inhabits forest streams and flooded forest.

Fowler's cory, Corydoras fowleri, is a long-snouted armoured catfish from the Amazon basin in Peru. Also known as the 'huanta cory' and 'milegros cory', it is often confused with C. coriatae and C. semiaquilus, and aquarium fish are regularly misidentified. Most long-snouted cories grow larger and are more aggressive than other Corydoras, and this one is suitable only for larger community aquaria.

The Pastaza cory, Corydoras pastazensis, is an armoured catfish from the upper Río Pastaza basin in Ecuador and the ríos Ucayali and Puinahua in Peru. The Río Tigre form was raised to species status as C. orcesi, a decision not followed by all authorities. The two are relatively easy to tell apart: in C. pastazensis the dark vertical bar breaks up or tapers off low on the body, and the body is peppered with numerous small dark spots.

The sailfin characin, Crenuchus spilurus, is a crenuchid from much of the Amazon and Orinoco drainages and coastal rivers of the Guianas. The only described member of its genus, it varies considerably in colour pattern and morphology across that range. It lives in tea-stained forest streams, and its timid, predominantly benthic nature means it does not always make an ideal community fish. Males guard eggs laid on the roof of a small cave, often formed from leaf litter.

Cynodon gibbus is a cynodontid from much of the Amazon basin, the middle and lower Orinoco, and the Rupununi River in Guyana. A pelagic fish of main river channels and larger tributaries, it grows to around 280 mm SL. It is rare in the trade but arguably more suitable for the home aquarium than some of its better-known relatives, given its size and relatively docile behaviour. Being easily dominated, it is best kept alone or with similarly sized, non-aggressive fishes.

Gastrodermus gracilis, long known as Corydoras gracilis, is a small armoured catfish from the central Amazon basin in Brazil, known from the rio Juriti in Pará to the rio Juma in Amazonas. Sometimes called 'shy cory' in the hobby, it has a lightish body with a dark arched stripe along the upper flank, a pattern shared with Brochis arcuata, C. narcissus and Hoplisoma urucu. Only in G. gracilis does the stripe end at the base of the upper caudal-fin rays. It apparently favours minor tributaries with dense riparian vegetation and acidic, tannin-stained water.

The tail-spot pygmy cory, Gastrodermus hastatus, long known as Corydoras hastatus, is a tiny armoured catfish with a wide range across the Amazon and Río Paraguay basins. It is known from Brazil, Bolivia, Paraguay and northeastern Argentina. Unlike most congeners it swims in midwater, forming mixed schools with similarly patterned small characids such as Serrapinnus kriegi. It is frequently confused with G. pygmaeus, but has a dark, roughly diamond-shaped spot on the caudal peduncle where G. pygmaeus has a dark lateral stripe.

Geophagus abalios is a cichlid from black and clear water tributaries of the río Orinoco in Venezuela, across the Llanos and south to the Casiquiare. One of the more commonly-traded members of the genus, it is rarely sold under the correct name and usually misidentified as G. altifrons or G. surinamensis. Juveniles are available cheaply because it is one of the few Geophagus bred commercially. Vertically split anterior flank bars separate it from the very similar G. brokopondo.

Geophagus altifrons is a large cichlid from the middle-to-lower Amazon basin in Brazil, including the Xingu, Tapajós, Madeira, Negro and Purus. Despite being the type species it is among the most frequently-misidentified members of the genus, partly because populations from the Orinoco, the Guianas and the Tocantins are now species in their own right. In adults the dark midlateral marking is reduced to 1-2 scales or absent, a feature unique to the species, but juveniles are very difficult to identify.

Geophagus argyrostictus is a cichlid known only from the rio Xingu system in Brazil, including its major tributary the rio Iriri. It belongs to the five species outside the G. surinamensis group, all with a complete infraorbital stripe, and fish over 70 to 80 mm SL develop silvery reflective scales on the anterior flanks. Markedly more aggressive than most congeners, it is a substrate-spawner and does best in a group of 5-8.

Geophagus dicrozoster is a cichlid from tributaries of the río Orinoco in Venezuela, extending to the Casiquiare and the headwaters of the Negro. Commonly traded but rarely under the correct name, it is usually sold as G. altifrons or G. surinamensis, and it is one of the few Geophagus bred commercially. Seven flank bars, the fourth and fifth meeting in a 'Y', and a relatively elongate profile identify it. It appears restricted to acidic blackwater.

Geophagus megasema is a cichlid from the upper rio Madeira basin, recorded from the Mamoré and Guaporé drainages in Bolivia and Brazil. Very rare in the aquarium hobby, it has been collected, bred and distributed by some private collectors. It has no dark preopercular or infraorbital markings, no bars on the flanks and a relatively large, roundish midlateral marking.

Geophagus proximus is a large cichlid from the Amazon system in Peru and Brazil, from the río Ucayali along the Solimões-Amazon to the rio Trombetas. Rare in the hobby, its name is often attached to shipments of other Geophagus species. It has a dark preopercular marking, no bars on the flanks and a large, roughly oblong midlateral marking. It is found mostly in the lower reaches of rivers and in floodplain lakes, favouring clear and black water.

Geophagus sp. 'orange head' is an undescribed cichlid confined to the lower rio Tapajós in Brazil, including its tributary the rio Arapiuns. Now one of the more readily available members of the genus, it has suffered from commercial breeders who do not cull deformed fry. Two forms exist, one misleadingly traded as G. sp. 'Araguaia orange head', and the orange on the head is most extensive in dominant adult males.

Geophagus sp. 'Pindaré' is an undescribed cichlid known only from the rio Pindaré in Maranhão state, north-eastern Brazil. It appears to belong to the G. surinamensis group and is quite easily identified by its deep head and body and proportionately large eye. The trade name G. sp. 'Pindare' (Parnaíba) is confusing, because G. sp. 'Parnaíba' is now described as G. parnaibae. Parts of the Pindaré have been heavily degraded by siltation.

Geophagus winemilleri is a cichlid from southern Venezuela and probably northern Brazil, recorded from the upper Río Negro, Río Siapa and Casiquiare. It is rare in the hobby, though other species are sometimes sold under its name. A dark preopercular marking and four ventrally-inclined bars on each flank help identify it, and it may be restricted to acidic blackwater.

Burgess' cory, Hoplisoma burgessi, long known as Corydoras burgessi, is an armoured catfish apparently endemic to the upper rio Negro basin in Brazil. One of several similarly patterned congeners, including H. adolfoi, H. davidsandsi and H. duplicareum, it has a black marking restricted to the area beneath the dorsal fin and extending into it, with a yellowish patch on top of the head. Rio Negro habitats are mostly blackwater tributaries and flooded forest.

Hoplisoma copei, long known as Corydoras copei, is an armoured catfish from Peru, apparently endemic to the Río Pastaza basin and possibly the lower Río Marañón. It is not well known and rarely traded. It looks very similar to several congeners, particularly H. acrense and H. cruziense, and little has been written about it since its description.

The Santa Cruz cory, Hoplisoma cruziense, long known as Corydoras cruziensis, is an armoured catfish from the Bolivian portion of the Río Madeira basin. The precise extent of its range is unclear and may include the Mamoré and Beni drainages. It is not well documented, but is said to differ from C. punctatus in having larger dark body markings, which form an irregular midlateral stripe in some specimens.

Sand's cory, Hoplisoma davidsandsi, long known as Corydoras davidsandsi, is an armoured catfish apparently endemic to the rio Unini system in the lower rio Negro basin, Brazil. One of a group of rio Negro species with an oblique dark bar along the back, it shares with H. melini a bar that splits in two above the caudal peduncle. It has a pale orange area between the facial stripe and dorsal bar and no further dark markings on the flanks.

The palespotted cory, Hoplisoma gossei, long known as Corydoras gossei, is an armoured catfish from the rio Mamoré watershed in Rondônia state, northwestern Brazil. It is also likely to occur in northern Bolivia, since the Mamoré forms the border between the two countries at the type locality. Also known as 'smokey cory' and 'Gosse's cory', it shares its colour pattern with Brochis seussi from the same river, which has a noticeably prolonged snout. A form referred to as 'CW069' appears intermediate between the two.

The julii cory, Hoplisoma julii, long known as Corydoras julii, is an armoured catfish from coastal river systems south of the Amazon delta in northeastern Brazil. Also known as 'leopard cory' or 'three-lined cory', it is often confused with H. trilineatum from the upper Amazon, and many fish traded as C. julii are that species. H. julii has numerous small, distinct spots on the head, where H. trilineatum has vermiform markings, though some H. trilineatum are spotted too.

Hoplisoma kanei, long known as Corydoras kanei, is an armoured catfish that appears to be native to the rio Negro basin in Brazil, possibly only the rio Branco drainage. Before description it was assigned the 'C' numbers C026 and C046. It is most easily confused with H. atropersonatum and sometimes traded as that species, but has dark markings in the anal and caudal fins, more numerous and smaller dark spots on the body, and a darker base colouration.

The false bandit cory, Hoplisoma melini, long known as Corydoras melini, is an armoured catfish from tributaries of the rios Negro, Caquetá and Orinoco in Brazil and Colombia. Its oblique dark bar along the back splits into two above the caudal peduncle, a feature shared only with H. davidsandsi, from which the dark markings on its flanks separate it. The rio Tiquié population is known in the hobby as 'C084', and a similar, slightly larger form from Peru as 'C085'.

The Xingu cory, Hoplisoma xinguense, long known as Corydoras xinguensis, is a small spotted armoured catfish from creeks in the upper Rio Xingu basin in Mato Grosso, Brazil. It is also sold as the dust cory, and fish traded under the C-numbers C055 and C105 to C108 have all been identified as this species. Dias et al. (2024) moved it to Hoplisoma as Hoplisoma xinguense. One of the smaller corys, it is best kept in a group of ten or more.

The vampire tetra, Hydrolycus scomberoides, is a predatory dogtooth characin from the central and upper Amazon in Brazil, Bolivia, Peru and Ecuador. Also sold as 'scomb' and 'sabre tooth tetra', it is regularly confused with the much larger payara, H. armatus. At up to 300 mm it still needs a huge tank and specialist care, and newly-imported specimens often refuse anything but live food.

The snowball pleco (L102), Hypancistrus inspector, is a suckermouth catfish from the upper rio Negro in Brazil and the Casiquiare in Venezuela. Brown to black with large whitish to yellow spots, it is most similar to H. contradens. It is normally collected from rocky rapids, is a cave-spawner with male brood care, and should not be kept with other Hypancistrus in order to prevent hybridisation.

The king tiger plec, Hypancistrus seideli, is a suckermouth catfish from the lower rio Xingu in Pará state, northern Brazil. Described by Sousa et al. in 2025, it is traded as L066 and L333 and also as 'network pleco' and 'scribbled pleco'. Its colour pattern is highly variable and it is regularly confused with L400. It inhabits turbulent whitewater rapids, much of which is likely to be severely degraded by the Belo Monte dam.

L260, the queen arabesque pleco, is an undescribed Hypancistrus known only from the lower rio Tapajós in Pará state, northern Brazil. Among the most popular loricariids in the hobby, it is available on a regular basis. The larger L411 from the rio Jarí looks similar, but in L260 the white vermiculations are significantly finer. The area where it is collected would be largely destroyed should a planned hydroelectric project go ahead.

L136 is an undescribed Hypancistrus from the rio Negro basin in Amazonas state, Brazil, collected in particular from the rio Demini. Highly variable in colour pattern, it has been assigned a series of L-numbers as a result. A peaceful cave-spawner with male brood care, it has been bred regularly in aquaria, but should not be kept with other Hypancistrus in order to prevent hybridisation.

The zebra plec, Hypancistrus zebra (L046), is a small loricariid catfish from the Rio Xingú basin in Brazil, named for its zebra pattern. Brazil banned its export in 2004 and captive-bred fish are expensive. Shy and easily outcompeted for food, it needs warm water of 26 to 30 °C, high oxygen levels and pristine conditions, and does not suit the general community tank.

Hyphessobrycon agulha is a small tetra known with certainty only from the rio Madeira system in the Amazon basin of Brazil, Peru and Bolivia. Relatively rare in the hobby, it is occasionally traded as the 'red-tailed flag tetra'. It lends its name to a group of closely-related species with a dark lower half of the body, especially above the anal fin, and it is very peaceful.

The flag tetra, Hyphessobrycon heterorhabdus, is a characid from Pará and Maranhão states in eastern Brazil, also known as 'Belgian flag tetra'. Its name has been misapplied to similar fishes across much of the Amazon, the Orinoco and the Guianas, and the true species may reach no further upstream than the rio Tapajós. It lives almost exclusively in small, shaded forest streams called igarapés.

The Loreto tetra, Hyphessobrycon loretoensis, is a small characid from the upper Amazon basin in Colombia, Peru and Ecuador. It is relatively popular in the hobby, but most traded fish are wild-caught, so availability can be sporadic. Most records are from forest streams and minor tributaries with tea-coloured water, overhanging vegetation and leaf litter.

The black stripe tetra, Hyphessobrycon melanostichos, is a characid endemic to the Rio Doze de Outubro in the upper Rio Tapajos basin, Brazil. It shares a number of similarities with Hyphessobrycon sp. 'Blue Ribbon' but has a lighter, more streamlined body, a smaller humeral spot and red colouring. It can become territorial in small tanks, but a group of 10 or more should prevent problems.

The Peruvian tetra, Hyphessobrycon peruvianus, is a characid known only from the upper Amazon basin in Peru. Popular in the trade, it is sometimes confused with H. loretoensis and H. metae and has repeatedly appeared under the latter name in aquarium literature. A more elongate body, a dark band reaching the tips of the median caudal-fin rays and red markings at the base of both caudal lobes set it apart.

The lemon tetra, Hyphessobrycon pulchripinnis, is a characid from central Brazil, mostly recorded from the rio Tapajós basin. It is bred commercially in several countries, but the origin of the aquarium strain is questionable. Fish identical to it have been photographed in the lower Xingu, while a related 'orange red' form from the Tapajós may not be the same species.

The flame-back bleeding heart tetra, Hyphessobrycon pyrrhonotus, is a characid endemic to the rio Negro system in Amazonas state, Brazil. The smallest of the three 'bleeding heart' species, it alone has a red, wedge-shaped patch along the upper body from below the dorsal fin to the base of the caudal. It lives in shallow blackwater tributaries near Barcelos, among roots, branches and leaf litter.

Hyphessobrycon vilmae is a small characid that appears to be endemic to the upper rio Tapajós basin in Amazonas and Mato Grosso states, Brazil. It is occasionally traded as 'chocolate neon tetra', and has a continuous, solid dark lateral stripe with no obvious humeral blotch. Generally peaceful, it is best kept in a mixed-sex group of at least 8-10.

Traded as the 'red line lizard tetra', Iguanodectes adujai is a characin from the rio Negro in Brazil and the upper Río Orinoco in Venezuela. It is exported alongside the similar-looking I. geisleri, and differs in lacking the black lateral stripe beneath the red stripe and in having 28 to 34 anal-fin rays (20 to 25 in I. geisleri). It is assumed to live in smaller tributaries containing pristine blackwater.

Iguanodectes geisleri is a characin from the rios Madeira and Negro in Brazil and the upper Río Orinoco in Venezuela. Traded with the similar-looking I. adujai as the 'red line lizard tetra', it differs in having a black lateral stripe beneath the red stripe and 20 to 25 anal-fin rays (28 to 34 in I. adujai). Adult males carry red markings in the pectoral, pelvic, anal and caudal fins.

The green line lizard tetra, Iguanodectes spilurus, is a characin found throughout the Amazon, Orinoco, Essequibo and Tocantins river systems. The most widespread Iguanodectes species, it has also been called the 'slender', 'spindle' or 'iguana' tetra, and differs from its congeners in its translucent dorsal and anal fins, lack of a red lateral stripe and prominent dark caudal-fin marking. It is sensitive to poor water conditions.

The striped headstander, Laemolyta taeniata, is an anostomid from the central Amazon basin, also recorded from the Orinoco system in Venezuela. The largest-growing member of the genus, to 288 mm SL, it is rarely seen in the aquarium trade. Something of a habitat generalist, it migrates into flooded forest in the wet season and has been seen in large migratory shoals with Leporinus fasciatus and L. agassizii. Water quality is of the utmost importance, and anostomids are prodigious jumpers.

The sturgeon catfish, Lamontichthys filamentosus, is a loricariid from the central and western Amazon in Brazil, Peru, Ecuador and Bolivia. Above 60 mm SL the pectoral-fin spine extends into a filament that can be over four times the length of the first branched ray, and the dorsal-fin spine carries a similar extension. Relatively common in the hobby but not easy to maintain, it needs clean, well-oxygenated water and a mature aquarium with plenty of algae-covered surfaces.

Leporinus brunneus is an anostomid from the rios Madeira and Negro in Brazil, the Orinoco in Venezuela and Colombia, and the Casiquiare canal. The largest officially recorded specimen measured 256 mm, and an aquarium with base dimensions of at least 210 by 60 cm is needed.

The banded leporinus, Leporinus fasciatus, is an anostomid from the Amazon and Orinoco systems and coastal Guyana, Suriname and French Guiana. Young fish are often sold without warning of their size and requirements, and it is fairly ubiquitous in public aquarium displays. It is frequently confused with L. affinis, and its dark body bars multiply with age, from five in young fish to around ten in adults.

The threespot leporinus, Leporinus friderici, is an anostomid from much of the Amazon system, with further records from the Guianas and Trinidad. It grows to 350 to 400 mm and needs an aquarium with base dimensions of at least 240 by 90 cm. Across this enormous range the fish differ in morphology and, especially, colour pattern.

The serpae tetra, Megalamphodus eques, is a characid with an enormous range through much of the Amazon drainage and the Río Paraguay. Very common in the trade, it is also sold as the 'jewel', 'red minor', 'blood' or 'callistus' tetra, and ornamental strains include 'long-finned' and 'balloon' forms. It has a reputation for nipping the fins of tankmates, although this is most pronounced when too few are kept or space is limited.

The bleeding heart tetra, Megalamphodus erythrostigma, is a characid from the upper Amazon basin where the borders of Brazil, Peru and Colombia meet. The best-known of three similar species in the 'bleeding heart' subgroup, it has the reddish humeral spot found in no other characid. Generally peaceful, although adult males are territorial to an extent, it mostly inhabits sluggish tributaries, side arms and forest lakes.

The black phantom tetra, Megalamphodus megalopterus, is a characid from the upper rio Madeira and upper rio Paraguai in Bolivia and Brazil. Most records are from the rio Guaporé (Río Iténez in Bolivia). Popular in the hobby and bred commercially in several countries, it is also available as a 'long-finned' strain. Adult males have black fins with the pelvic, dorsal and anal enlarged, while females are deeper-bodied with reddish pelvic, anal and adipose fins.

The lesser bleeding heart tetra, Megalamphodus socolofi, is a characid known only from the rio Negro basin and the rio Nhamundá in Brazil. One of three similar species in the 'bleeding heart' subgroup, it shares their reddish humeral spot, found in no other characid. Generally peaceful, although adult males are territorial to an extent, it mostly inhabits sluggish tributaries, side arms and forest lakes.

Metynnis lippincottianus is a spotted silver dollar from Brazil and French Guiana, found in the lower and middle Amazon and the Oyapock system. It is occasionally seen for sale, sometimes as 'silver dollar', and its spotted pattern tells it apart from M. argenteus and M. hypsauchen. The spots are less pronounced than in M. maculatus, with which it shares a common name. The precise extent of its range is unclear.

The spotted metynnis, Metynnis maculatus, is a silver dollar probably confined to the upper rio Madeira and upper rio Paraguai in Bolivia and Brazil. It is most often confused with M. argenteus and M. lippincottianus, but it has more midlateral scales and more spines on the ventral keel than either. It schools in nature and needs a very large tank with a group of six or more.

The Bolivian ram, Mikrogeophagus altispinosus, is a cichlid endemic to the upper rio Madeira basin in Bolivia and Brazil. Also traded as 'hi-fin ram' and 'Bolivian butterfly', it is larger and less colourful than M. ramirezi and lacks its blue iridescent markings, and it is arguably a better choice for less-experienced aquarists. A soft, sandy substrate is essential, and it needs pristine water quality.

The smallest member of its genus, Nannostomus anduzei is a pencilfish from the upper Orinoco in Venezuela and the rio Negro basin in Brazil. Rarely traded in numbers, it is a relatively common contaminant among shipments of wild fishes from Manaus. Males have an intensely red caudal peduncle and anal-fin, and its size and timid nature suit a tank of its own or diminutive tankmates such as Paracheirodon simulans.

The golden pencilfish, Nannostomus beckfordi, is a lebiasinid widely distributed across Guyana, Suriname, French Guiana, Brazil and Venezuela. The type species of the genus and fairly ubiquitous in the trade, it is less demanding than most congeners and a good choice for a newcomer. Many fish on sale are farmed, and wild populations vary in colour pattern, several having been described as species now considered synonyms of N. beckfordi.

The twostripe pencilfish, Nannostomus digrammus, is a lebiasinid from the central Amazon basin in Brazil and the Rupununi basin in Guyana. Rare in the hobby, it usually arrives as bycatch among shipments of other fishes. It is most similar to N. bifasciatus but has an adipose-fin, and its small size and timid nature make it a poor community fish.

The hockeystick pencilfish, Nannostomus eques, is a lebiasinid from the central and upper Amazon, the Orinoco drainage and rivers of Guyana. It swims at an oblique angle, a trait shared only with N. unifasciatus among congeners, and is also known as the 'rocket', 'diptail' or 'tubemouth' pencilfish. Genetic research on rio Negro populations raises the possibility that the species may be a complex of cryptic taxa.

The dwarf pencilfish, Nannostomus marginatus, is a lebiasinid of Guyana, Suriname and the middle-to-lower Amazon in Peru, Colombia and Brazil. Enduringly popular, it lacks the red body colour of males of the related N. mortenthaleri and N. rubrocaudatus, showing three dark lateral stripes with no red or purple between them. Colour varies between populations, and its small size and timid nature make it a poor community fish.