Aquarist Atlas
Fish by water

Hard and alkaline water fish

Fish of hard water and of alkaline, buffered water, grouped by the lake or river they come from and its cited chemistry.

1,411 species from 14 waters

Two kinds of water are listed. Hard water: the habitat water named on the fish's page is measured slightly hard, hard or very hard. Alkaline, buffered water: lakes whose general hardness is modest but whose water is alkaline and buffered. Keepers often call the second kind hard; by general hardness it is not, so it gets its own heading.

Hard water

Measured slightly hard to very hard.

Lake Tanganyika · 258 fish

Habitat water hard · 600–690 µS/cm Source: The Physical Limnology of Lake Tanganyika, August–December 1995 (FAO/FINNIDA, Technical Document).

Lake Edward · 48 fish

Habitat water hard · 878–1,130 µS/cm Source: Lake Edward (AFR-12) databook — ILEC World Lake Database (physical dimensions, water quality, fauna, fishery trends).

Lake Kivu · 21 fish

Habitat water very hard398 ppm Source: Source book for the inland fishery resources of Africa, Vol. 1 (Vanden Bossche & Bernacsek 1990), FAO CIFA Technical Paper 18/1 — lake entries compiling EAFRO, Talling & Talling 1965, Welcomme 1972, Van Der Ben 1959, Reusens 1987, Verbeke 1957.

Lake Albert · 16 fish

Habitat water slightly hard157 ppm Source: Source book for the inland fishery resources of Africa, Vol. 1 (Vanden Bossche & Bernacsek 1990), FAO CIFA Technical Paper 18/1 — lake entries compiling EAFRO, Talling & Talling 1965, Welcomme 1972, Van Der Ben 1959, Reusens 1987, Verbeke 1957.

Sea of Galilee (Lake Kinneret) · 10 fish

Habitat water hard Source: "Kinneret is a hard-water, mildly saline freshwater lake" — Salinity in Lake Kinneret: History, Challenges and Management (A. Rimmer, IOLR / Kinneret Limnological Laboratory).

Nile River · 9 fish

Habitat water hard Source: "The Nile is a hard-water, alkaline river, chemically a world apart from the soft equatorial headwaters." — Seasonal variations in physicochemical parameters of Nile river water in Giza, Egypt (BMC Biotechnology, 2025).

Cuatro Ciénegas · 6 fish

Habitat water hard Source: "The pozas are alkaline and hard, typically near neutral to mildly basic — source springs run around pH 7..." — Using Chemical Data to Define Flow Systems in Cuatro Ciénegas (Evans, 2005).

Laguna de Apoyo · 6 fish

Habitat water hard268 ppm Source: Barlow, Baylis & Roberts (1976), Chemical Analyses of some Crater Lakes in Relation to Adjacent Lake Nicaragua (Univ. Nebraska, DigitalCommons).

Laguna de Xiloá · 4 fish

Habitat water very hard443 ppm Source: Chemical Analyses of some Crater Lakes in Relation to Adjacent Lake Nicaragua (Barlow, Baylis & Roberts, 1976) — Lake Jiloá temperature, oxygen, pH, conductivity & ion chemistry profiles.

Rio Grande · 2 fish

Habitat water hard Source: "The water is hard and alkaline throughout" — Climate and Water Monitoring at Amistad National Recreation Area, WY2023 (U.S. National Park Service).

Alkaline, buffered water

General hardness is modest; the water's alkalinity and buffering are what set it apart.

Lake Malawi · 844 fish

Habitat water moderately soft, alkaline, well-buffered79 ppm Source: Branchu, Bergonzini, Ambrosi, Cardinal, Frédérique, Delalande, Pons-Branchu & Benedetti (2010). Hydrochemistry (major and trace elements) of Lake Malawi (Nyasa), Tanzanian Northern Basin. Hydrol. Earth Syst. Sci. Discuss. 7: 4371–4409.

Lake Victoria · 175 fish

Habitat water soft, alkaline, buffered25 ppm Source: Source book for the inland fishery resources of Africa, Vol. 1 (Vanden Bossche & Bernacsek 1990), FAO CIFA Technical Paper 18/1 — lake entries compiling EAFRO, Talling & Talling 1965, Welcomme 1972, Van Der Ben 1959, Reusens 1987, Verbeke 1957.

Lake Managua (Xolotlán) · 6 fish

Habitat water moderately soft, strongly alkaline, soda-type114 ppm Source: Cole, G.A. (1976). Limnology of the Great Lakes of Nicaragua, Table 2 (major ions in meq/L; Swain 1961; Lin 1961). In: Investigations of the Ichthyofauna of Nicaraguan Lakes, Univ. Nebraska.

Lake Nicaragua (Lago Cocibolca) · 6 fish

Habitat water soft, mildly alkaline61–62 ppm Source: Cole, G.A. (1976). Limnology of the Great Lakes of Nicaragua, Table 2 (major ions in meq/L; Swain 1961; Lin 1961). In: Investigations of the Ichthyofauna of Nicaraguan Lakes, Univ. Nebraska.

Only waters with cited measurements count. A fish whose range spans waters of different character is left off rather than given one water's figures.

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