Fish Suitable For Coldwater Tanks: How To Choose Species For Indoor Unheated Aquariums (2021)


Please bear in mind that the following groupings are given as a guide only. You should read up on the species you are interested in for more detail about their temperaments and water quality requirements.

Fish that are sold for “coldwater” aquariums are better classified as “temperate” species. They do not so much need cooler water, rather, they are species that have a wide temperature tolerance and are able to withstand temperature fluctuations. Because of this ability, they can be kept in unheated aquariums indoors, but only a few types can tolerate the extremes of the temperature outdoors in ponds. Some other species that are generally regarded as tropical can tolerate cooler water than the recommended 24 to 26°C, but are stressed by temperature fluctuations. These can be kept in unheated aquaria – but only if the temperature is stable and within the range they can tolerate.

Nearly all of these “coldwater” species can also be kept in tropical tanks, but check individual species for temperature requirements.

Small fish suitable for indoor unheated aquariums

Many of these species can also be mixed with medium to large-sized non-aggressive species. For more information about the species, click the info link.

Common Name (Species name)

  • Black Widow tetra (Gymnocorymbus ternetzi)
  • Zebra danio (Danio rerio)
  • Pearl danio (Danio albolineatus)
  • Leopard danio (Danio frankei)
  • White cloud mountain minnow (Tanichthys albonubes)
  • Bronze, Albino and Peppered corydoras (Corydoras aeneus, C. paleatus)
  • Gold medaka (Ozyrias latipes)
  • Murray River rainbow (Melanotaenia fluviatilis)
  • Western pygmy perch (Edelia vittata)
  • Southern pygmy perch (Nannoperca australis)
  • Olive glassfish (Ambassis agassizii)
  • Desert goby (Chlamydogobius eremius)

Medium to Large fish suitable for indoor unheated aquariums – non-aggressive

Some of these species can be mixed with aggressive or predatory types. See notes on individual species. For more information about the species, click the info link.

Common Name (Species name)

  • Rosy barb (Puntius conchonius)
  • Odessa barb (Puntius ticto var odessa)
  • China barb (Puntius semifasciolatus)
  • Giant danio (Danio aequipinnatus)
  • Bitterling (Rhodeus amarus)
  • Paradise fish (Macropodus opercularis)
  • Mountain galaxias (Galaxias olidus)
  • Western galaxias (Galaxias occidentalis)
  • Spotted or common galaxias, jollytail (Galaxias maculatus)
  • Common Name (Species name)
  • Black moor and telescope (Carassius auratus)
  • Fantail (Carassius auratus)
  • Comet and Shubunkin (Carassius auratus)
  • Celestial and bubble-eye (Carassius auratus)
  • Lionhead and ranchu (Carassius auratus)
  • Oranda – including blue and redcap (Carassius auratus)
  • Pearlscale (Carassius auratus)
  • Pompom (Carassius auratus)
  • Butterfly tail and Panda (Carassius auratus)
  • Ryukin (Carassius auratus)
  • Sucking catfish (Gyrinocheilus aymonieri)

Medium to large fish suitable for indoor unheated aquariums – agressive, predatory or territorial

Some of these species can be mixed with large non-aggressive species. See notes on individual species for cautions. For more information about the species, click the info link.

Common Name (Species name)

  • Tandanus catfish (Tandanus tandanus)
  • Golden perch (Macquaria ambigua)
  • Australian Bass (Macquaria novemaculeata)
  • Murray cod (Maccullochella peelii)
  • Spangled perch (Leiopotherapon unicolor)
  • Silver perch (Bidyanus bidyanus)

===> Further Reading ===>

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