Every species

Pseudogastromyzon laticeps is a balitorid loach from southeastern China, apparently endemic to the Longjin river drainage in Guangdong province. Like its congeners it has a flattened head and body with horizontally orientated paired fins, adapted to shallow, fast-flowing, highly-oxygenated streams. Based on the images available it appears to have reddish dorsal and caudal fins, and males develop tubercules on the head at sexual maturity.

Traded as the 'Chinese hillstream loach', Pseudogastromyzon myersi is a balitorid from Hong Kong and neighbouring Guangdong province, China. The commonest member of the genus in the hobby, it has often been misidentified as P. cheni, which is not collected for the trade. Aquarium Pseudogastromyzon with a yellow-based dorsal fin and a red distal band should be considered P. myersi. It needs clean, well-oxygenated water and has been bred in aquaria on numerous occasions.

The giant whiptail catfish, Pseudohemiodon laticeps, is a loricariid from the rios Uruguay, Paraná and Paraguay in Brazil, Paraguay and Argentina. Growing to 300 mm, it stays buried in soft substrate by day and emerges to feed at night, so a sandy substrate and very clean, stable water matter most. The male is a paternal 'lip brooder', carrying the eggs on his labial barbels for 12-14 days, and the species has been bred in aquaria.

Pseudohomaloptera leonardi is a 'lizard' loach ranging through Peninsular Malaysia and north into Thailand as far as the Tapi river drainage. Seriously Fish referred to it as Homaloptera sp. 'H01' before its identity was established. It is very similar to P. sexmaculata, and both are sometimes misidentified as H. yunnanensis. Naturally reclusive, it needs clean, fast-flowing, well-oxygenated water and a group of four or more.

Pseudohomaloptera sexmaculata is a hillstream loach from central and western Thailand, known only from the Chao Phraya and Mae Klong watersheds. An obligate dweller of swiftly-flowing streams and headwaters, it needs clean, well-oxygenated water. It closely resembles P. leonardi, and both are sometimes misidentified as P. yunnanensis. Members of the group mostly turn up as contaminants among shipments of other species and are usually sold as 'gecko' loaches.

The neon blue-eye, Pseudomugil cyanodorsalis, is a euryhaline blue-eye from coastal northern Australia and possibly southern New Guinea. Males are told apart from the rest of the genus by the bright metallic blue upper portion of the body, the source of the alternative name 'blueback blue-eye'. It has been recorded from full marine conditions to pure fresh water, and is generally considered to do better in brackish water. Timid and easily outcompeted, it is unsuitable for the general community.

The forktail blue-eye, Pseudomugil furcatus, is a small pseudomugilid endemic to the Northern and Milne Bay provinces of eastern Papua New Guinea. Aquarium stock is bred commercially and apparently derives from a single collection in 1981, so inbreeding can bring reduced fertility and a high rate of deformity in fry. It inhabits heavily-vegetated, clear forest streams and suits a densely-planted, well-chosen community aquarium.

The spotted blue-eye, Pseudomugil gertrudae, is a pseudomugilid from northern Australia, Papua New Guinea and the Aru Islands, eastern Indonesia. Wild populations are isolated from one another and differ in colour pattern, body size and fin morphology, but the fish on sale are of a single, commercially produced ornamental strain. Dark spots in the dorsal, anal and caudal fins separate it from other members of the genus except P. paskai and Pseudomugil sp. 'red neon'.

The Pacific blue-eye, Pseudomugil signifer, is the most widely-distributed blue-eye in Australia, found along most of the eastern coastline. Its habitats range from full marine conditions to pure fresh water, and northern populations often grow considerably larger than southern ones. Recent unpublished analyses apparently suggest it may comprise two or more distinct taxa, and wild fish from the northern and southern ends of its range would not hybridise in captive experiments.

Pseudomugil sp. 'red neon' is an undescribed blue-eye, possibly collected near Timika in Papua province, Indonesia. It first appeared in the hobby in 2011 under names including P. sp. cf. paskai and P. 'iriani'. Initially suspected to be a hybrid or selectively-bred form of P. paskai, it has been shown by DNA sequencing to be an undescribed species close to P. gertrudae and P. paskai. Peaceful but easily outcompeted, it suits a densely-planted aquarium.

The delicate blue-eye, Pseudomugil tenellus, is a euryhaline blue-eye with a patchy but wide range in coastal northern Australia. Sometimes called the 'Arnhem Land blue-eye', it is most easily identified by the midlateral scale row, a series of pale spots with darker spaces between that become more conspicuous with age. It is particularly common in densely-vegetated swamps, billabongs and slow-moving streams, and also occurs on the Aru Islands and in southern Papua New Guinea.

The Asian bumblebee catfish, Pseudomystus siamensis, is a bagrid from the lower Mekong and the Chao Phraya river in Thailand. It was formerly placed in Leiocassis, a name still used in much of the literature, and similarly patterned congeners may be sold under its name. Shy and nocturnal, it hides among submerged roots by day, will eat any tankmate small enough, and is territorial towards other bottom-dwellers.

The false Asian bumblebee catfish, Pseudomystus sp. cf stenomus, is a bagrid from southeastern Thailand and peninsular Malaysia. Usually imported as P. stenomus, which is endemic to Java, it seems to be an undescribed species, and it lacks the striped bumblebee pattern of P. siamensis. Shy and nocturnal, it lurks among roots and rocks in fast-flowing, sandy-bottomed streams by day, and will eat any tankmate small enough.

The giant bumblebee catfish, Pseudopimelodus bufonius, is distributed throughout northeastern South America, from Venezuela to eastern Brazil. Its range extends from the Lake Maracaibo basin, and it grows to 245 mm SL. The type locality is uncertain but probably Cayenne, French Guiana.

The barred shovelnose, Pseudoplatystoma fasciatum, is a large pimelodid catfish with a very wide range in South America, from Colombia to Argentina. Recorded at 104 cm and 70 kg, it reaches close to that size quickly in captivity and can live for well over 20 years, so it is debatable whether it should be considered an aquarium subject at all. It is easily confused with P. tigrinum, and both are usually sold as 'tiger shovelnose'.

The tiger shovelnose, Pseudoplatystoma tigrinum, is a large pimelodid catfish native to the Amazon and Rio Orinoco basins. It grows to around 105 cm and reaches close to that size quickly in captivity, so it is debatable whether it should be considered an aquarium subject at all. It is easily confused with P. fasciatum, which is usually sold under the same name, though P. tigrinum is generally the more uniformly striped. Hybrids with the red-tailed catfish also reach the market.

The spiketail paradisefish, Pseudosphromenus cupanus, is a small labyrinth fish restricted to southern India and Sri Lanka. It lives in sluggish and still waters such as rice paddies, swamps and weedy ponds. It lacks the two dark lateral stripes of its only congener, P. dayi. A secretive bubble nester, it is peaceful but too small and timid for most community aquaria.

The brown spike-tailed paradise fish, Pseudosphromenus dayi, is a small labyrinth fish from coastal drainages of the Western Ghats in Kerala, India. It is known only from the Chalakkudy, Muvattupuzha and Periyar rivers, though it may be more widely distributed. Two dark, irregular lateral stripes on the head and body, and a more extended caudal fin in males, separate it from its only congener, P. cupanus. A secretive bubble nester, it is peaceful but small and timid.

Pseudotropheus cyaneorhabdos is an mbuna endemic to Lake Malawi, known from one locality on the northeastern shore of Likoma Island. Formerly known as Melanochromis 'maingano', it is sometimes incorrectly sold as 'electric blue' johanni. Dominant males are bluish overall, where the similar P. johannii has more black patterning. Aggressive and territorial, it should not be kept with Melanochromis, as they may hybridise.

Pseudotropheus johannii is an mbuna endemic to Lake Malawi, found in shallow rocky coastal areas around Masinje Rocks and Cape Ngombo. Males are blue-black with bright blue striping and females orange. The blacker dominant males separate it from the bluer P. cyaneorhabdos, and it is sometimes sold as 'electric blue johanni'. Less aggressive than most Melanochromis, it can be housed with similarly-sized mbuna. It is still often sold as Melanochromis johanni.