Every species

Aristochromis christyi is a predatory cichlid endemic to Lake Malawi, found throughout the lake but most commonly in intermediate zones. Growing to 300 mm SL, it is not particularly common in the lake or the hobby. Its beak-like mouthparts are adapted for hunting small fish in crevices between rocks, and it also ambushes prey, sometimes rolling onto its side as it approaches then taking it with a fast sideways motion.

The African red-eyed tetra, Arnoldichthys spilopterus, is a characin endemic to Nigeria, where it occurs in the Ogun and lower Niger river systems. Also known as the 'large-scaled African characin' or 'Niger tetra', it has large scales compared with most relatives and is hardy once settled. In the wild it is relatively scarce, known from fewer than 10 localities in an area of extensive deforestation and pollution.

Aspidoras pauciradiatus is a small armoured catfish that appears restricted to the upper Araguaia basin in Goiás state, Brazil. Sometimes called the 'false corydoras' or 'sixray corydoras', it has 6 soft dorsal-fin rays against 7 in other Aspidoras, plus a distinctive colour pattern. Aspidoras are told from the very similar Corydoras mainly by having two cranial fontanels.

Aspidoras raimundi (C125) is a small armoured catfish from coastal river drainages in north and northeastern Brazil. The fish sold as A. spilotus, from Ceará state, is now treated as the same species. A peaceful, schooling species, it grows to around 45 mm SL.

Aspidoras taurus is a small armoured catfish known only from the upper Itiquira and Taquari rivers, in the rio Paraguay system of Mato Grosso, Brazil. Relatively common in the aquarium trade, it is sometimes mislabelled as A. menezesi, a valid but distinct species. Thick skin covering the infraorbitals, preopercle and reduced nuchal plate separates it from congeners.

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.

Leopold's tetra, Astyanax leopoldi, is a characid native to the Approuague and Oyapock river basins in French Guiana and Brazil. It is most common in fast-flowing waters, where it swims in large shoals in marginal or calmer areas. Like most Astyanax, it is rarely offered for sale.

The blind cave tetra, Astyanax mexicanus, is a characid found from Texas and New Mexico in the southern United States through Mexico into Guatemala. The eyeless, troglomorphic form lives only in underground caves in Mexico and is produced in huge numbers on Far Eastern farms, while the surface form is rarely seen in the hobby. The two may have diverged within the last 10,000 years, and the blind form finds its way with its lateral line.

The alligator gar, Atractosteus spatula, is a gar from the lower Mississippi basin and Gulf Coast states of the south-eastern USA and Mexico. One of the largest freshwater fishes in the world, it reaches a recorded 3050 mm and can live well over 50 years, so it should not be considered a home aquarium subject. Juveniles are seen for sale quite regularly, and a hybrid with Lepisosteus platostomus is known as the 'crocodile gar'.

The Cuban gar, Atractosteus tristoechus, known locally as 'manjuari', is a gar endemic to western Cuba and Isla de la Juventud. Endangered across most of its range, it grows to 1800 mm SL and lives for several decades, so it should not be considered a home aquarium subject. Captive breeding efforts are well-established, and some public aquaria maintain it long-term.

The tropical gar, Atractosteus tropicus, is a gar from Caribbean and Pacific-slope drainages of Central America, from southern Mexico to Costa Rica. It grows to 1250 mm SL and can live for several decades, so it should not be considered a home aquarium subject, though juveniles are occasionally offered in the trade. Like other gars it can breathe atmospheric air to a certain extent through a modified, vascularised swim bladder.

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.

The new yellow regal peacock, Aulonocara baenschi, is a cichlid endemic to Lake Malawi, known from five sites along the lake's western shoreline. It inhabits intermediate zones where rocky shores give way to sand with scattered rocks, usually at 4 to 6 metres. Also sold as the 'yellow regal cichlid', 'Baensch's peacock', 'sunshine peacock' and 'Nkhomo-Benga peacock', it is most easily told from similar congeners by its steeper, more curved snout.

The northern aulonocara, Aulonocara ethelwynnae, is a cichlid endemic to Lake Malawi, known only from Chitande Island and the nearby northwest shore. Quite rarely seen in the hobby, it is most easily distinguished by the chocolate-brown striping of mature males. In intermediate zones, females and immature males form loose schools at around 3 metres while mature males hold territories deeper, at 6 to 7 metres.

The red shoulder peacock, Aulonocara hansbaenschi, is a cichlid endemic to Lake Malawi, known from four localities on its southeastern shore. Some authors regard it as a geographical variant of the highly variable A. stuartgranti. It is also sold as the 'firebird cichlid' and 'red peacock'. At Masinje it shows a distinct preference for rocky caves and crevices in 3 to 6 metres of water, where most of the genus forage over sand.

The Malawi butterfly, Aulonocara jacobfreibergi, is a cichlid endemic to Lake Malawi, living where rocky shores give way to sand. One of the larger members of the genus, with males reaching 150 to 170 mm, it was among the first Aulonocara species in the hobby and is also sold as 'Freiberg's peacock' and 'fairy cichlid'. Males react aggressively to fish with a similar colour pattern, so tankmates need choosing with care.

The sulphurhead peacock, Aulonocara maylandi, is a cichlid endemic to Lake Malawi, where it occurs in two principal colour forms. Males from West Reef and Eccles Reef, in the southeast of the lake, carry a bright yellow band from the snout along the back and dorsal-fin margin. At Kande Island, off the central-western shore, the stripe is whitish and both sexes have an enlarged lower pharyngeal bone. That population was described as A. maylandi kandeensis, a name still widely used in the hobby.