Every species

The Chinese false gudgeon, Abbottina rivularis, is a small bottom-dwelling cyprinid native to China, the Korean peninsula and southern Japan. It has been widely introduced elsewhere, including the Mekong and Salween basins, Taiwan, Turkmenistan and Kyrgyzstan, and is considered invasive. It has started to appear in the aquarium trade and should never be released into natural waters outside its native range.

The red-tailed squirrel loach, Aborichthys elongatus, is a nemacheilid loach from Darjeeling District, West Bengal, in north-east India. It lives among rocks and cobbles in shallow, swift streams running down from the Sivalik Hills into the Teesta and Brahmaputra drainage. The species is quite rare in the trade, and most fish sold under the name are collected at lower altitudes in Jalpaiguri District and probably represent different species.

Aborichthys sp. 'AR01' is a nemacheilid loach, apparently undescribed, known only from the Raidak I River basin in West Bengal, India. It is usually traded as A. elongatus, but that species appears endemic to higher-altitude waters in Darjeeling District, and the colour and patterning of the two are clearly different. It inhabits shallow, swiftly-flowing water over gravel and small rocks.

Aborichthys sp. 'AR02' is a small nemacheilid loach, apparently undescribed, known only from the Raidak I River basin in West Bengal, India. It occasionally turns up as a contaminant in shipments of A. sp. 'AR01'. Its small adult size, which seems to be 30 to 35 mm SL, and its relatively wide dark vertical bars along the body and single reddish bar in the caudal fin set it apart from others in the genus.

The marbled headstander, Abramites hypselonotus, is an anostomid from the Amazon, Orinoco and Paraguay-Paraná basins in South America. An ecological generalist, it occurs in turbid main river channels, minor tributaries and backwaters, and enters inundated zones during the annual floods. Best kept as a group in a large tank alongside cichlids, characins and catfishes, it may nip long or trailing fins and eat soft-leaved plants.

The polka dot lyre tail pleco, Acanthicus adonis, is a very large loricariid catfish from the rio Tocantins in Brazil. Thought to range across much of the Amazon basin, it is traded as spotted juveniles in quite large numbers despite its patent unsuitability for aquaria. It reaches 600 mm or more, loses its spotted patterning as it matures and becomes increasingly belligerent with age, so it can only be recommended to owners of the largest private aquaria or tropical ponds.

The lyre tail pleco, Acanthicus hystrix, is a very large loricariid catfish from the Amazon region of Brazil and Peru. A handful of records come from the Orinoco in Venezuela. Juveniles are traded in quite large numbers, but it can reach at least 1000 mm in nature and 500 to 600 mm in captivity, and becomes increasingly belligerent with age. Young fish are easily told from A. adonis by lacking its white to yellowish body spots.

The peacock loach, Acanthocobitis pavonacea, is a large nemacheilid loach from the Brahmaputra River drainage in Assam, northeastern India. At 120 to 156 mm SL it is one of the largest nemacheilids, and Singer and Page (2015) treat it as the only member of Acanthocobitis. It isn't common in the trade, but occasional specimens turn up among wild-caught shipments from northeast India, sometimes sold as 'panther' or 'puma' loach.

Acanthocobitis sinuata is a nemacheilid loach from peninsular India, described from Wayanad district in Kerala. It appears widespread in drainages south of the Krishna. Most authorities treat it as a synonym of A. mooreh, but the two differ in distribution, dorsal-fin ray count and colour pattern, and they are apparently being revalidated. Both have a reduced lateral line ending around the dorsal fin, which in the similar A. botia is complete or ends above the anal fin.

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.

Acanthopsoides molobrion is a dwarf horse-faced loach from Borneo, Peninsular Malaysia and southern Thailand. Like others in the genus it lives in flowing, clear-water river channels over sand, fine gravel or mud, and needs a soft, sandy substrate because it spends some of its time completely buried. Several Acanthopsoides in the trade have proven very tricky to identify. This one has 10 to 15 mid-dorsal markings and three bands in the caudal fin.

Acanthopsoides robertsi is a dwarf horse-face loach from the Kapuas River basin in West Kalimantan, Indonesian Borneo. Unlike most of its congeners it is quite easily identified, being the only species with a dark, triangular marking in the caudal fin. Very similar fish have been collected further north in the Kayan and Sambas basins. Highly gregarious, it needs soft sand to bury in and is best kept in a group of six or more.

Acanthopsoides sp. 'A01' is an unidentified dwarf horse-face loach of unknown origin, likely to be collected in Thailand or Peninsular Malaysia. Like several of its congeners in the trade it has proven very tricky to identify. It spends some of its time completely buried, so it needs a soft, sandy substrate, and it is best kept in a group of six or more. SF member Mark Duffill has recovered fry from an adult pair kept on their own in a small tank.

Acanthopsoides sp. 'A02' is an unidentified dwarf horse-face loach of unknown origin, likely to be collected in Thailand or Peninsular Malaysia. Like several of its congeners in the trade it has proven very tricky to identify. A soft, sandy substrate is essential because it spends some of its time completely buried, and it is highly gregarious and best kept in a group of six or more.

The horseface loach, Acantopsis dialuzona, is a cobitid loach from Sumatra, Borneo, Java and Peninsular Malaysia, and possibly Thailand. Most literature lists it as A. choirorhynchos, which Kottelat treats as a junior synonym, and few if any fish in the trade come from near the type locality, so they may represent an unidentified species. Juveniles are exported in large numbers but adults are uncommon in the hobby, and it needs soft sand to bury in.

The threadfin acara, Acarichthys heckelii, is a cichlid from the northern Amazon basin in Colombia, Peru and Brazil and the Essequibo in Guyana. The only member of its genus, it grows to around 200 mm and digs incessantly, and it is susceptible to deteriorating water quality. Some adults show sudden, extreme aggression towards conspecifics that can kill weaker fish, and the problem decreases as tank and group size increase.

The green whiptail, Acestridium dichromum, is a small loricariid catfish from the upper rio Negro in Brazil and the upper Orinoco in Venezuela. It is known only from those two basins and the drainages between them, including the Casiquiare Canal.

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.