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Coldwater fish

These species come from cool or subtropical water and live happily without a heater in a room that stays above about 16 °C.

  1. Cherry shrimp

    Neocaridina davidi

    Bright red dwarf shrimp that graze all day and breed in a planted tank; tiny bioload, but fry are snacks for most fish.

    1.6 in · 4+ gal · 72–75°F · pH 6.5–7.8

  2. Amano shrimp

    Caridina multidentata

    The best-known algae-eating shrimp, made famous by Takashi Amano; bigger than cherries and a good fit for planted community tanks.

    2 in · 7+ gal · 72–77°F · pH 6.5–7.5

  3. Black widow tetra

    Gymnocorymbus ternetzi

    A hardy, deep-bodied tetra with black 'skirt' fins; easy for beginners, but a small group nips the fins of its tank mates.

    2.4 in · 22+ gal · 68–79°F · pH 6–7

  4. Goldfish

    Carassius auratus

    The coldwater classic with hundreds of breeds; lives 10–15 years or more, makes lots of waste and needs a roomy, well-filtered tank.

    5.9 in · 24+ gal · 50–75°F · pH 6.5–8

  5. Peppered cory

    Corydoras paleatus

    One of the hardiest corys: a mottled catfish that sifts sand in a group of six and prefers slightly cooler water.

    2.8 in · 22+ gal · 72–79°F · pH 6–7

  6. Rosy barb

    Pethia conchonius

    A large, hardy barb whose males turn bright pink-red when breeding; suits cooler tanks that run without a heater.

    3.9 in · 28+ gal · 64–72°F · pH 6–8

  7. White Cloud Mountain minnow

    Tanichthys albonubes

    A small, hardy minnow with red fins that needs no heater; ideal for an unheated tank kept at room temperature.

    1.6 in · 17+ gal · 64–72°F · pH 6–8

  8. Zebra danio

    Danio rerio

    A fast, striped danio and one of the hardiest beginner fish; schools near the surface and is happy at room temperature.

    1.5 in · 26+ gal · 64–75°F · pH 6–8

  9. African clawed frog

    Xenopus laevis

    A fully aquatic frog, most often sold as an albino; easy and long-lived, but a predator that eats any fish it can fit in its mouth.

    5.9 in · 13+ gal · 63–75°F · pH 6.8–7.8

  10. Bladder snail

    Physella acuta

    A small left-coiled snail that usually hitchhikes in on plants; a self-fertilising hermaphrodite, so a single one starts a colony.

    0.6 in · 1+ gal · 63–84°F · pH 7–8

  11. Dwarf orange crayfish

    Cambarellus patzcuarensis

    A bright orange crayfish of about 1.5 inches and the only popular crayfish that fits a planted tank with peaceful fish.

    1.6 in · 10+ gal · 64–79°F · pH 6.8–8

  12. Marbled crayfish

    Procambarus virginalis

    The only known clonal crayfish: every one is female and breeds without males, so a single animal can found a colony of hundreds.

    3.9 in · 19+ gal · 64–77°F · pH 7–8

  13. Ramshorn snail

    Planorbarius corneus

    The classic flat-coiled snail every fishkeeper knows; it cleans up film and leftovers, breeds easily, and the red form is especially popular.

    1.4 in · 4+ gal · 70–81°F · pH 7–8

  14. Red swamp crayfish

    Procambarus clarkii

    A hardy but aggressive American crayfish that digs burrows, wrecks plants and eats snails and fish; invasive in many countries and banned in the EU.

    3.9 in · 25+ gal · 68–79°F · pH 7–8.5

  15. Axolotl

    Ambystoma mexicanum

    A Mexican salamander that keeps its feathery gills for life; it needs cool water below 68°F, so it never shares a tropical tank.

    9.8 in · 13+ gal · 57–68°F · pH 6.5–8

  16. Celestial pearl danio

    Danio margaritatus

    A tiny, pearl-spotted danio with orange fins, the star of planted nano tanks; shy, with males sparring constantly.

    0.8 in · 13+ gal · 72–75°F · pH 6.5–7.5

  17. Crystal red shrimp

    Caridina logemanni

    The red-and-white bee shrimp, benchmark of the shrimp hobby; it needs soft, acidic, very stable water, usually on aquasoil and RO water.

    1.2 in · 6+ gal · 68–77°F · pH 5.5–7

  18. Denison barb

    Sahyadria denisonii

    A large, torpedo-shaped barb with a red line along its body; peaceful but very active, needing a long tank with flow and spotless water.

    4.3 in · 76+ gal · 59–77°F · pH 6.8–7.8

  19. Ghost shrimp

    Palaemonetes paludosus

    A cheap, see-through North American shrimp whose insides are visible; easy to keep, but short-lived and often hard on fry and shrimplets.

    1.9 in · 7+ gal · 64–82°F · pH 7–8

  20. Giant danio

    Devario aequipinnatus

    A big, fast danio with blue and gold stripes that needs a long tank, current, very clean water and a tight lid.

    3 in · 76+ gal · 72–75°F · pH 6–8

  21. Gold barb

    Barbodes semifasciolatus

    A golden aquarium form of the Chinese green barb; peaceful, hardy and happy in cooler tanks without a heater.

    3 in · 26+ gal · 64–75°F · pH 6–8

  22. Medaka

    Oryzias latipes

    The Japanese rice fish: hardy, peaceful and ideal for an unheated tank or a summer pond, with hundreds of ornamental strains.

    1.4 in · 13+ gal · 64–72°F · pH 6.5–8.5

  23. Paradise fish

    Macropodus opercularis

    One of Europe's first aquarium fish: a hardy, striped labyrinth fish that lives without a heater, but males are pugnacious.

    3.1 in · 23+ gal · 61–72°F · pH 6–8

  24. Variatus platy

    Xiphophorus variatus

    A slightly larger, cooler-water relative of the platy; a peaceful livebearer for a community tank with hard water.

    2.8 in · 17+ gal · 68–79°F · pH 7–8.2

  25. Weather loach

    Misgurnus anguillicaudatus

    A long, cool-water loach that digs in sand and reacts to pressure changes; a good goldfish companion that reaches up to 11 inches.

    11 in · 76+ gal · 64–73°F · pH 6–8

  26. Chinese fire belly newt

    Cynops orientalis

    A small newt with a black back and bright orange belly that needs cool water and a patch of land; its skin is toxic, so it lives without fish.

    3.5 in · 14+ gal · 59–72°F · pH 6.5–7.5

  27. Great pond snail

    Lymnaea stagnalis

    A large coldwater pond snail that breathes air at the surface and eats soft plants and other snails' eggs; for coldwater tanks, not tropical planted ones.

    2 in · 7+ gal · 50–77°F · pH 7–8.5

  28. Iberian ribbed newt

    Pleurodeles waltl

    A large, hardy Spanish newt of 6 to 8 inches that is almost fully aquatic, likes cool water and quickly learns to take food from tweezers.

    7.1 in · 19+ gal · 59–68°F · pH 6.5–8

  29. Badis

    Badis badis

    A small chameleon fish that changes colour with its mood; a calm bottom-dwelling hunter that needs caves and live or frozen food.

    2.4 in · 23+ gal · 59–77°F · pH 6–7.5

  30. Butterfly hillstream loach

    Beaufortia kweichowensis

    A flat 'butterfly' loach from southern Chinese rivers that clings to rocks and glass and wants cool, fast, oxygen-rich water.

    3 in · 17+ gal · 61–75°F · pH 6.5–8

  31. Scarlet badis

    Dario dario

    A tiny, under-an-inch scarlet fish for nano tanks; it eats mostly live and frozen foods, and males split the tank into territories.

    0.8 in · 13+ gal · 64–79°F · pH 6.5–8.5

  32. Tiger hillstream loach

    Sewellia lineolata

    A flat, stingray-like loach from Vietnamese mountain streams that needs strong current, cool water and algae-covered rocks.

    2.6 in · 22+ gal · 68–75°F · pH 6–7.5

Every tank is different. Set yours up once (size, water, who already lives there) and each species is checked against it.

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