Every species

P14, Potamotrygon sp. 'Itaituba', is a freshwater stingray collected from the Rio Tapajos in Brazil. It is unclear whether it is a geographical variant of P. leopoldi or a distinct species. It is smaller, at around 40 cm across the disc, and its light spots are smaller, denser around the edge of the disc and extend to the underside. The name comes from Itaituba, the city the rays are sent to before being shipped on to Santarém.

The Maracaibo River stingray, Potamotrygon yepezi, is a freshwater stingray from the waters surrounding and feeding Lake Maracaibo in Venezuela. Strictly a freshwater species, it is absent from the brackish lake itself and apparently favours soft mud or sand substrates. Not large for a Potamotrygon at around 40 cm across the disc, it is often confused with P. reticulata, P. humerosa and P. scobina, and the Peruvian P. sp. 'Nazca' is unlikely to be this species.

The glass bloodfin tetra, Prionobrama filigera, is a characid recorded from the Amazon drainage in Ecuador, Colombia, Peru, Bolivia and Brazil. It is told from the other bloodfin tetra, Aphyocharax anisitsi, by its more elongate body and the lack of red in the anal and ventral fins. An active, pelagic species of the upper water layers, it grows to around 6 cm and should be kept in groups of at least six to eight.

The X-ray tetra, Pristella maxillaris, is a small characid native to coastal waters of Venezuela, Guyana, Suriname, French Guiana and northern Brazil. In the dry season it lives in clearwater streams, moving into flooded savannah to spawn when the rains come. Peaceful, hardy and inexpensive, it is commercially bred in huge numbers, and a semi-albino 'golden' strain exists. The only species in the genus, it appears in older literature as Pristella riddlei.

The Malabar leaffish, Pristolepis marginata, is a nandid endemic to the Western Ghats of Kerala, India, and is also known as the common catopra. Unlike many other nandids it inhabits flowing water, from fast-moving streams and rivers to some whitewater areas. It reaches 15 cm, will swallow any tankmate small enough to eat and can be a little belligerent, so it is best kept with similarly sized or larger fish that also suit flowing water.

The large-finned lampeye, Procatopus nototaenia, is a killifish thought to be endemic to the Lobi and Kienke river basins in southwestern Cameroon. It lives in shady forest streams with clear, moderately flowing water. Several colour forms are known by collection locality, among them 'Kribi', 'Edea' and 'Kopongo', and should never be mixed. The males carry the differences in colour and finnage, their dorsal, anal and caudal fins lengthening as they mature.

Known as the fenestratus, Protomelas fenestratus is a cichlid endemic to Lake Malawi, found in the northern and southwestern parts of the lake. It inhabits rocky shorelines and the sandy zones beyond them, feeding by blowing sediment from rocks and taking what it uncovers. A gentle species unsuited to the boisterous mbuna community, it should not be kept with P. taeniolatus or Protomelas sp. 'steveni taiwan reef', as they may hybridise.

Protomelas pleurotaenia is a cichlid endemic to Lake Malawi, known from Nkhata Bay and Monkey Bay, where it lives in vegetation between rock and sand. It feeds by blowing at the top layer of the substrate, usually sand, and eating the invertebrates it uncovers. Rare in the hobby, it is gentle and unsuited to the mbuna community, though it becomes territorial when breeding.

Protomelas sp. 'steveni taiwan reef' is an undescribed cichlid endemic to Lake Malawi, found at Taiwan Reef, Higga Reef and Mbamba Bay Island. Often sold as a subspecies of P. fenestratus, it is thought to be distinct, and adult males are told from P. fenestratus and P. taeniolatus by their bright red anal fin. Males hold territories on flat rock deeper than 20 metres, and in nature these can measure 5 or 6 feet across.

Protomelas taeniolatus is a cichlid endemic to Lake Malawi, where it is widespread over rocky areas of shallow, clear water. Very similar to P. fenestratus, it is one of the more popular Protomelas, and its colour forms include 'Red Empress', 'Super Red Empress' and 'Blue Fire'. Some of these may be reclassified as distinct species, as they reach different maximum sizes. Tougher than its congeners, it can even be kept with mbuna.

The African lungfish, Protopterus annectens, is a lungfish found in 17 African countries, including Senegal, Nigeria, Kenya and Sudan. It inhabits temporary floodplains that dry out completely for part of the year and survives the dry season by aestivating in a mucus cocoon, for several years if need be. The most commonly seen lungfish in the hobby, it reaches 100 cm, bites hard and is best kept singly.

The slender lungfish, Protopterus dolloi, is a lungfish from Gabon, Angola, the Central African Republic and both Congo republics. It inhabits floodplains, rivers, swamps and backwaters, and survives the dry season in a mucus cocoon, though it aestivates more rarely than P. annectens. It reaches 130 cm, lives for over 20 years and is best kept singly, since it can suddenly turn on tankmates.

The Buenos Aires tetra, Psalidodon anisitsi, is a characid from the Paraná and Uruguay river systems in Brazil, Paraguay, Argentina and Uruguay. A popular and hardy aquarium fish, it is also available as a line-bred albino strain, sometimes traded as 'golden'. It has a reputation for fin-nipping, though mostly when too few are kept or space is limited, and a group of at least 8-10 is the minimum. It is still often sold as Hyphessobrycon anisitsi.

Psalidodon balbus is a small characid known only from upper Paraná basin headwaters in the Federal District and Goiás, central Brazil. Most records come from the rio São Bartolomeu, including the Bananal, Santa Maria-Torto and Gama tributary systems.

L114, Pseudacanthicus cf. leopardus, is a loricariid collected mostly in the rio Negro basin in Brazil, particularly the rio Demini. P. leopardus was described from the Rupununi River in Guyana, so the identity of this fish remains unconfirmed. Traded as the Demini leopard cactus pleco or simply 'leopard cactus pleco', it grows to 250 mm and needs an aquarium of at least 180 x 60 cm set up to simulate a flowing river.

The three-spot headstander, Pseudanos trimaculatus, is an anostomid from Peru, Brazil and Guyana, found in small shoals in deeper water. It was formerly known as Anostomus trimaculatus, and that name is still used in much of the available literature. Aggressive towards its own kind in small numbers, it can be kept in groups of six or more in larger aquaria, and a well-fitting cover is essential since Pseudanos are excellent jumpers.

The orange chromide, Pseudetroplus maculatus, is a euryhaline cichlid native to peninsular India and Sri Lanka. It mostly inhabits brackish estuaries, coastal lagoons and the lower reaches of rivers, and can be kept in fresh or brackish water so long as acidic conditions are avoided. Wild examples are rarely seen in the hobby, where selectively bred strains traded as 'red' or 'yellow' chromide are widely available.

The dwarf Egyptian mouth-brooder, Pseudocrenilabrus multicolor, is a small cichlid from Egypt, Sudan, Uganda, Rwanda, Kenya and Tanzania. One of the first cichlids to be spawned in captivity, it has been in the hobby for over a century and breeds easily as a maternal mouth-brooder. The two subspecies, P. m. multicolor and P. m. victoriae, differ in colour and pattern and should not be kept together, to prevent hybridisation.

Pseudocrenilabrus nicholsi is a small mouth-brooding cichlid from the Democratic Republic of Congo, found in ponds, creeks and drainage ditches. Rarely seen in the hobby, it is a pugnacious little fish, and males are very aggressive towards one another, so a single male is best kept with several females. Some males develop long extensions to the ventral fins.

The southern mouth-brooder, Pseudocrenilabrus philander, is a cichlid found in eleven countries from the Democratic Republic of Congo to South Africa. It lives in streams, lakes, ponds and sinkholes, and some populations exist in slightly brackish conditions. Three subspecies are recognised, but as many as 11 distinct populations may exist and these should not be mixed in aquaria. Not often seen in the hobby, it appears to travel badly and losses are common.