Every species

Apistogramma macmasteri is a dwarf cichlid known only from the Río Guaytiquía and Río Metica basins in the upper Río Meta system, Colombia. Coded A120 under the DATZ system, it has a similar-looking, possibly conspecific population referred to as A122, and A121 is the ornamental 'red' form. Captive-raised fish are the recommended choice for the community aquarium.

Apistogramma mendezi is a dwarf cichlid from the lower rio Negro basin in northwestern Brazil, found in blackwater tributaries and flooded forest. Populations coded A220, A221 and A222 may be conspecific and differ in colour pattern, particularly the orientation of the caudal-fin markings. Most collections for the trade appear to come from further upstream, around Santa Isabel do Rio Negro or São Gabriel da Cachoeira.

Known in the trade as the 'panda dwarf cichlid', Apistogramma nijsseni is from tributaries of the Río Ucayali in Loreto Region, northern Peru. Coded A180 under the DATZ system, it inhabits slow-moving blackwater streams and creeks where the pH can drop as low as 4.0 or 5.0 and the substrate is littered with branches and a deep layer of rotting leaves.

Apistogramma norberti is a dwarf cichlid from the Río Tahuayo and Río Tamshiyacu, minor Amazon tributaries south of Iquitos in northeastern Peru. Known before its description as A. sp. 'großmaul' or 'bigmouth', and coded A190, its position within the genus is unresolved and it is only tentatively placed in the A. cacatuoides group. It lives in minor jungle streams whose volume changes significantly with the season.

Apistogramma panduro is a dwarf cichlid from the Río Ucayali drainage and the Río Tahuayo in Loreto Region, northern Peru. Also known as the blue panda cichlid and by the trade name A. sp. 'pandurini', it is told apart from similar species by a lower jaw that extends beyond the upper. It can be quite aggressive towards conspecifics, though pairs often remain monogamous once formed.

The pantaloon cichlid, Apistogramma pantalone, is a small cichlid probably endemic to the Nanay river system in northern Peru. It lives in shallow, hyper-acidic forest streams, and unlike many congeners does not fare well if water parameters deviate far from nature. A facultative mouthbrooder, it has been traded as A. sp. 'Lyretail 1' and is very similar to the closely related A. martini.

Apistogramma paulmuelleri (A52) is a dwarf cichlid apparently endemic to Loreto, Peru, described from a forest stream near the Iquitos to Nauta road. It has been traded as A. sp. 'Apache', a name also applied to other, non-conspecific Apistogramma. Since 2009 parts of the type locality stream have been degraded by removal of riparian vegetation.

Apistogramma sp. 'breitbinden' is an undescribed dwarf cichlid from the upper Rio Negro in Brazil, the Venezuelan Orinoco and the Inirida in Colombia. The German name means 'broad-banded' and refers to the uniformly broad suborbital stripe of males. Known in the hobby for several decades, it is often imported as bycatch among shipments of wild-collected A. iniridae, and some populations carry the DATZ codes A164, A165 and A167.

Apistogramma sp. 'Kelleri' is an undescribed dwarf cichlid known only from minor jungle tributaries near Leticia, Amazonas department, Colombia. First collected in 2008, it was exported again in 2009 and 2010 as A. sp. 'Jutai' and A. sp. 'diamond face', with a Brazilian collection site the exporter later corrected to Leticia. It has also appeared on trade lists as A. sp. 'Leticia', and belongs to the A. barlowi complex.

Steindachner's apisto, Apistogramma steindachneri, is a dwarf cichlid from the Essequibo, Demerara and other river systems of Guyana and Suriname. It lives in slower-moving tributaries and streams with leaf litter and submerged wood. The form from the Demerara drainage carries the DATZ code A138, and a very similar fish from the Cuyuni basin in eastern Venezuela (A139) may or may not be conspecific.

The three-striped apisto, Apistogramma trifasciata, is a dwarf cichlid from the Guaporé, Paraguay and middle Paraná basins. Found in Brazil, Paraguay and Argentina, it lives in sluggish creeks, tributaries and smaller rivers where leaf litter collects. A narrow third stripe from the pectoral-fin insertion to the anal fin helps separate it from congeners. The DATZ code is A204, with possibly conspecific forms from Argentina and the rio Guaporé coded A205 and A206.

The red edge apisto, Apistogramma viejita, is a dwarf cichlid from the upper Meta basin, part of the Orinoco system in Colombia. Many forms of A. macmasteri enter the trade incorrectly labelled viejita. Male A. viejita have a dark top edge to the dorsal fin and A. macmasteri does not. It inhabits shallow, slow-moving shoreline water with abundant riparian and emergent vegetation, often in savannah country.

The green panchax, Aplocheilus blockii, is a small killifish from Sri Lanka and southern India, growing to around 45 mm SL. Euryhaline, it mostly inhabits lowland, often coastal, still or slow-moving brackish or fresh water with surface vegetation or overhanging cover, and is commonly found in mangrove swamps and rice paddies.

The striped panchax, Aplocheilus lineatus, is a predatory killifish from peninsular India and northern Sri Lanka, growing to 10 cm TL. It lives in permanent water from mountain streams and lakes to swamps and rice paddies, and is not an annual species. The golden wonder panchax sold in the trade is a golden form selectively bred in the hobby that does not occur in the wild.

The dwarf panchax, Aplocheilus parvus, is a small killifish from Sri Lanka and Tamil Nadu state, southeastern India, growing to around 40 mm SL. Euryhaline, it mostly inhabits lowland, often coastal, still or slow-moving brackish or fresh water, and is commonly found in mangrove swamps and rice paddies.

The Baetican toothcarp, Apricaphanius baeticus, is endemic to a small part of southern Spain, mostly in the lower Guadalquivir River basin. It was considered a geographic variant of A. iberus until 2002, and differs in details such as thicker vertical bars in males and a few large dark markings in females. Only nine isolated populations remain, and it has been listed as endangered by the IUCN since 2006.

The Spanish toothcarp, or fartet, Apricaphanius iberus, is restricted to a few small areas of Spain's Mediterranean coast. These lie in Catalonia, Valencia and Murcia, and only 20 or so isolated populations remain, threatened by introduced Gambusia holbrooki and Fundulus heteroclitus, habitat degradation and pollution. Populations from the Atlantic coast and Algeria are now A. baeticus and A. saourensis.

The Sahara toothcarp, Apricaphanius saourensis, is endemic to the Oued Saoura, an endorheic river basin in Algeria that drains into the Sahara. Described in 2006, it differs from A. iberus and A. baeticus in its mottled body patterning. In 2004 it was found only at Mazzer, and introduced Gambusia is thought to have extirpated it from its other localities. The describers suggest it should be considered critically endangered.

The black ghost knifefish, Apteronotus albifrons, is a weakly electric knifefish from the upper half of South America, from Colombia to Paraguay. Usually sold at around 4 inches, it grows to 50 cm and needs a long-term housing plan. Its eyesight is very poor, and it navigates, finds prey and communicates using a weak electric field. In the wild it lives in swiftly flowing streams and rivers over sand.

The Colombian shark catfish, Ariopsis seemanni, is an ariid catfish from river mouths along the Pacific coast of the Americas, from Mexico to Peru. Usually sold as a silvery 2 to 3 inch juvenile, it grows to 350 mm SL and lives mostly in brackish water, so it is not recommended to those lacking the facilities to house it for life. Venom glands at the base of the first dorsal spine can cause a painful swelling.