Every species

The Asian red tailed catfish, Hemibagrus wyckioides, is a bagrid from the Mekong system in China, Laos, Vietnam, Cambodia and Thailand. It also occurs in the Chao Phraya drainage. The largest bagrid in central Indochina, it reaches at least 900–1000 mm and 70–80 kg, and the largest specimen known measured 1300 mm. Juveniles are sometimes sold, but buying them is strongly discouraged given its size, aggression and a lifespan of several decades.

The barbel steed, Hemibarbus labeo, is a cyprinid widespread in eastern Asia between the Yangtze and Amur river basins. A predominantly riverine fish of clear, well-oxygenated running water, it forms schools just above the substrate as an adult, and some populations make annual spawning migrations. Adults lack dark spots on the body and have a long snout and well-developed lips.

Hemibarbus longirostris is a cyprinid native to far eastern Asia, including northeastern China, southeastern Russia, the Korean peninsula and Japan. A predominantly riverine fish, it lives in clear, well-oxygenated running water over sand, gravel, rock or mud, and adults tend to form schools just above the substrate in slower-moving sections.

The spotted steed, Hemibarbus maculatus, is a cyprinid widespread in eastern Asia between the Yangtze and Amur basins, including Taiwan and Hainan. It has 7–11 large blackish spots on each flank and a deep body with a clearly convex dorsal profile. A riverine fish of clear, well-oxygenated running water, it breeds in May and June, depositing its eggs among aquatic vegetation. It has probably been introduced to Vietnam and Laos, or records from there represent another species.

Hemibarbus mylodon is a cyprinid endemic to the Korean peninsula, where it occurs throughout North Korea and South Korea. A predominantly riverine fish, it lives in clear, well-oxygenated running water over sand, gravel, rock or mud, and adults tend to form schools just above the substrate in faster-flowing sections.

The five star general, Hemichromis elongatus, is a highly aggressive cichlid recorded from Guinea, Cameroon, Angola, Namibia, Botswana and Zimbabwe. The common name comes from the row of five dark markings along its flanks. A piscivore, it eats any fish it can fit into its mouth, does not tolerate conspecifics outside a pair and is best kept in a species tank. The patchy recorded range suggests it has been misidentified in places or occurs in more countries.

The blood-red jewel cichlid, Hemichromis lifalili, is a cichlid endemic to the Democratic Republic of Congo. Often confused with H. bimaculatus, it has two black spots on the flanks against that species' three, and its round midlateral marking sits above the lateral line, unlike the oval one of the red form of H. guttatus. It becomes very aggressive when spawning but is fairly placid otherwise, and is not a particularly good species for the community tank or for newcomers to cichlids.

The barrigona tetra, Hemigrammus barrigonae, is a small characin from the Rio Meta and Orinoco basins in Colombia and Venezuela. It inhabits slow-moving rivers and tributaries. Not a common species in the hobby, it occasionally shows up as a contaminant among imports of more popular species. Like all Hemigrammus, its taxonomic status is Incertae Sedis, and most experts agree the genus needs a full revision.

The dash-dot tetra, Hemigrammus bellottii, is a small characin from the Rio Solimões, Negro and Maroni basins in Brazil and French Guiana. It is not common in the trade, and most specimens come in as contaminants among batches of more popular species. Like all Hemigrammus, its taxonomic status is Incertae Sedis, and most experts agree the genus needs a full revision.

Boesman's tetra, Hemigrammus boesemani, is a small characin officially recorded from Suriname, French Guiana and Peru. It favours sluggish and still waters. Very rare in the hobby, it was once considered a subspecies of H. micropterus. The recorded range suggests it has been misidentified in at least one of these countries or occurs in others as well.

The shiny copper tetra, Hemigrammus cupreus, is a small characin known only from the Rio Solimões in Brazil. It lives in the turbid white water of the river itself and in flooded habitats including the lakes known as várzeas, where conditions are far less acidic than in blackwater. Not common in the hobby, it occasionally shows up as a contaminant among imports of more popular species.

The glowlight tetra, Hemigrammus erythrozonus, is a small characin known only from the Rio Essequibo in Guyana. Hardy and inexpensive, it is one of the best choices for a newcomer to fishkeeping. All fish in the trade are mass-bred on commercial farms, and a selectively-bred albino form is also sold. In nature it lives in forested tributaries with tannin-stained, often highly acidic water, and it is more colourful in acidic conditions.

The January tetra, Hemigrammus hyanuary, is a small characin from the Amazon basin in Peru and Brazil. Also known as the costello or green neon tetra, it resembles an elongated head and tail light tetra, H. ocellifer, and is occasionally confused with it. The type specimen came from Lake Hyanuary near Manaus. It inhabits slow-moving rivers, tributaries and floodplain lakes and tends to lose colour in alkaline water.

Hemigrammus levis is a small characin native to the Brazilian Amazon, found in slow-moving rivers, tributaries and floodplain lakes. A rather rare fish in the UK hobby, it occasionally shows up as a contaminant among imports of more popular species. Like all Hemigrammus, its taxonomic status is Incertae Sedis, and most experts agree the genus needs a full revision.

The golden tetra, Hemigrammus rodwayi, is a small characin native to Guyana, Suriname, French Guiana, Peru and Brazil. Its normal colour is a rather dull silvery grey. In some areas wild fish react to a trematode parasite with metallic gold deposits of guanin in the skin, and these were once described as a separate species, H. armstrongi. Captive-bred fish are not exposed to the parasite, so most 'golden tetras' on sale lack the gold colour.

The red-base tetra, Hemigrammus stictus, is a small characin from Venezuela, Guyana and Brazil. It inhabits slow-moving rivers, tributaries and floodplain lakes. Not often seen for sale, it occasionally shows up as a contaminant among imports of more popular species. Like all Hemigrammus, its taxonomic status is Incertae Sedis, and most experts agree the genus needs a full revision.

The broken-line tetra, Hemigrammus ulreyi, is a small characin known only from the Brazilian part of the Rio Paraguay basin. Other species are frequently misidentified as H. ulreyi, and the true fish is quite scarce in the hobby. It inhabits slow-moving rivers and tributaries. Like all Hemigrammus, its taxonomic status is Incertae Sedis, and most experts agree the genus needs a full revision.

The featherfin tetra, Hemigrammus unilineatus, is a small characin widespread across northern South America, from Venezuela to Peru and Brazil. Despite its abundance in nature it is not commonly seen in the hobby, and usually turns up only as a contaminant among imports of other species. A very peaceful shoaling fish, it inhabits slow-moving rivers, tributaries, oxbow lakes and ditches, some clear and others murky with sediment.

Hemigrammus vorderwinkleri is a small tetra known only from the Rio Negro in Brazil, where it inhabits blackwater rivers and tributaries. It is most likely to be seen as a contaminant among imports of other species. A very peaceful shoaling fish growing to around 40 mm SL, it suits a blackwater biotope or a heavily planted tank, since fish on sale will almost certainly be wild caught.

Hemimyzon formosanus is a balitorid loach endemic to Taiwan, most abundant in rivers draining the western slopes of the Central Mountain Range. Current knowledge suggests it is the most widely distributed of the three Hemimyzon species endemic to the island. It lives in shallow, fast-flowing, highly oxygenated headwaters and needs clean, well-oxygenated water, a biologically mature tank with plenty of biofilm, and a tight cover since it can climb glass.