Aquarist Atlas
Tetras · waters

The waters behind the fish

Tetras are creatures of specific water: a tannin-black Río Negro igapó, a white-sand upper-Amazon creek, an Orinoco llanos channel, a clear Guianan forest river, a Congo rapids. Knowing which system a species comes from — its flow regime and water chemistry — is the foundation of keeping it well. Here are the freshwater systems that shaped 1,217 of the 1,451 species in this atlas.

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Río Negro & the blackwaters

104 species

South America · north-western Amazon

The great blackwater rivers — the Negro and its tributaries, draining white-sand (podzol) catchments that leach tannins and almost no minerals. Acidic, soft and the colour of strong tea, this is the heartland of the cardinal tetra (Paracheirodon axelrodi) and a host of small characins adapted to ion-poor water.

Central Amazon & the várzea

426 species

South America · central Amazon lowlands

The main stem of the Amazon (Solimões) and its nutrient-rich whitewater floodplain — the várzea — together with the flooded blackwater forest, the igapó. The seasonal flood pulse that drowns the forest each year drives the feeding and breeding of countless tetras in the leaf litter and submerged roots.

Upper Amazon & the Andean piedmont

49 species

South America · western Amazon (Peru, Ecuador, Bolivia)

The headwaters where the Amazon is born on the eastern slope of the Andes — the Ucayali, Marañón, Napo and the clear, fast piedmont streams of Peru, Ecuador and Bolivia. A centre of small-characin diversity, with many Hyphessobrycon, Hemigrammus and stevardiine tetras described from single foothill creeks.

Orinoco basin

73 species

South America · Venezuela & eastern Colombia

The Orinoco and the vast seasonal grasslands of the llanos, draining Venezuela and the eastern Colombian plains. Clearwater and blackwater tributaries alike — the Inírida, Atabapo and Ventuari — hold cardinal and other tetras, which flood out across the savanna each wet season.

The Guianas & the Shield

67 species

South America · the Guiana Shield

The coastal rivers draining the ancient Guiana Shield to the Atlantic — the Essequibo, Courantyne, Maroni and Oyapock of Guyana, Suriname and French Guiana. Clear, tannin-tinged forest rivers over rock and white sand, home to a distinct fauna of tetras, hatchetfish and pencilfish.

Paraná–Paraguay & the Pantanal

176 species

South America · the La Plata basin

The great southern river system — the Paraná, Paraguay and Uruguay draining to the Río de la Plata, and the vast Pantanal wetland at its heart. Cooler and more seasonal than the Amazon, these waters hold their own characins, including many Astyanax and the larger silver tetras of the open channels.

Eastern Brazil & the São Francisco

94 species

South America · the Brazilian Atlantic coast

The São Francisco — Brazil's great interior river — and the short, isolated rivers of the Atlantic Forest coast from Bahia to Paraná. Long separated from the Amazon, these eastern drainages have produced narrow-range endemic characins found nowhere else.

Trans-Andean rivers

114 species

South America · north-western Andes (Colombia, Ecuador)

The rivers west of the Andes, cut off from the Amazon by the cordillera — the Magdalena–Cauca of Colombia, the Atrato, and the Pacific-slope drainages of Ecuador. An isolated characin fauna, including trans-Andean Hyphessobrycon and stevardiine tetras with no Amazonian relatives nearby.

Congo basin

80 species

Africa · the Congo River

The second-largest river on Earth and the centre of African-tetra diversity. The Congo and its forest tributaries — the rapids of the lower river, the dark Cuvette Centrale, the Kasai and the Ubangi — are home to the shimmering Congo tetra (Phenacogrammus interruptus) and a wealth of alestid characins.

Niger, Volta & West Africa

16 species

Africa · the Upper & Lower Guinea coast

The rivers of West Africa — the Niger and its inland delta, the Volta, Senegal and Gambia, and the short coastal rivers of the Upper Guinea forest. Seasonally pulsing Sudano-Sahelian and forest waters where Brycinus, Alestes and Micralestes school in numbers.

Lower Guinea & the Ogowe

8 species

Africa · the Atlantic forests of Gabon & Cameroon

The high-rainfall coastal rivers of the Lower Guinea forest — the Ogooué of Gabon, the Sanaga and the rivers of southern Cameroon and Equatorial Guinea. Clear, fast forest waters draining to the Atlantic, with an endemic-rich characin fauna distinct from the Congo's.

Nile & East Africa

7 species

Africa · the Nile and the eastern lakes

The Nile and the rivers and lakes of eastern Africa — the White and Blue Nile, Lake Turkana and the Sudd wetlands. Open, often turbid waters where the larger alestids and the predatory tigerfishes (Hydrocynus) hunt in the main channels.

Zambezi & southern Africa

3 species

Africa · the Zambezi and the Okavango

The Zambezi, the Okavango Delta and the rivers of south-central Africa. Warm, seasonally flooded systems where the striped robber (Brycinus lateralis) and the fearsome tigerfish (Hydrocynus vittatus) are mainstays of the open water.

South America — other drainages

227 species

South America · Neotropics

Neotropical species whose recorded range falls outside, or spans, the named basins above. South America is the centre of characin diversity, and its hydrography is intricate; many small tetras are known from only a handful of localities.

Africa — other drainages

7 species

Africa · Afrotropics

African alestid species whose recorded range falls outside, or spans, the named basins above — a reminder that the African tetras, though fewer than their American cousins, range across most of the continent's fresh waters.

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