Keeping fish without heating at room temperature.
Coldwater aquarium species include a large group of fish requiring various living conditions. This category includes a large number of species from temperate regions of North America, Europe, and Japan; many coldwater fish are well-known inhabitants of mountain rivers. Their unifying characteristic is their adaptability to life in an unheated room aquarium. The temperature in such an aquarium ranges between 14-25 degrees.
Most coldwater fish need a large amount of dissolved oxygen in the water, which makes keeping them indoors difficult. They live only in large vessels, and even then only with aeration or water flow and low temperatures; powerful filters should be placed in the aquarium. They require a spacious, low, and wide aquarium with a good oxygen regime, with a substrate of pebbles, coarse sand, or coarse gravel. Most representatives of coldwater species are undemanding, can tolerate both low and relatively high temperatures for a short time, and therefore can be fully recommended for beginner aquarists.
All breeds of goldfish can be divided into two large groups: long-bodied and short-bodied. Short-bodied goldfish, compared to long-bodied ones, are rather delicate creatures, because the deformation of the natural body shape for the species does not go unpunished, and the adaptation ability of short-bodied breeds has turned out to be significantly reduced. The optimal temperature should be considered 18-25°C in the spring-summer period, and 14-21°C in winter. The most coldwater ones are: Comet, Shubunkin.
Color Koi Carp. Juveniles can survive in home aquariums, but adult fish feel much better in garden ponds. It is best to keep them in basins. They can withstand water temperature drops down to 3-4°C.
Most egg-laying toothcarps live better in unheated aquariums, because high temperatures shorten their lifespan.
It must be remembered that selection, hybrid, albino species, and species bred in amateur aquariums for a long time are more thermophilic than those taken from natural conditions.
Some species of fish that can be kept in an unheated aquarium at room temperature.
Carassius auratus Subunkin Calico — Carassius auratus Comet.
Cyprinus carpio koi — Cyprinus carpio koi.
Acipenser ruthenus — Scaphirhynchus platorynchus.
Noturus lachneri — Ameiurus melas.
Corydoras aeneus — Scleromystax barbatus.
Misgurnus anguillicaudatus — Misgurnus fossilis.
Aborichthys elongatus — Mesonoemacheilus triangularis.
Barbatula barbatula — Liniparhomaloptera disparis.
Balitora brucei — Homaloptera bilineata.
Leptobotia guilinensis — Sinibotia robusta.
Garra rufa — Traccatichthys pulcher.
Schistura pridii — Protomyzon pachychilus.
Nemacheilus corica — Botia almorhae.
Rhinogobius candidianus — Rhinogobius nandujiangensis.
Beaufortia leveretti — Sewellia lineolata.
Gastromyzon ctenocephalus — Sinogastromyzon puliensis.
Pseudogastromyzon fangi — Neogastromyzon crassiobex.
Rhoadsia altipinna — Rhodeus ocellatus.
Lepomis megalotis — Lepomis gibbosus.
Aphanius sirhani — Aphanius mento.
Chapalichthys pardalis — Allotoca dugesii.
Gambusia nobilis — Gambusia holbrooki.
Girardinichthys multiradiatus — Girardinichthys viviparus.
Goodea atripinnis — Ilyodon whitei.
Heterandria formosa — Lucania goodei.
Skiffia bilineata — Phalloceros caudimaculatus.
Zoogoneticus tequila — Xenoophorus captivus.
Characidium rachovi — Characodon lateralis.
Elassoma okefenokee — Elassoma gilberti.
Phoxinus erythrogaster — Notropis chrosomus.
Poecilia reticulata — Poecilia reticulata.
Badis pyema — Badis badis.
Raiamas christyi — Devario auropurpureus.
Mimagoniates microlepis — Jordanella floridae.
Rasboroides vaterifloris — Astyanax mexicanus.
Danio choprae — Danio dangila.
Devario assamensis — Devario devario.
Danio nigrofasciatus — Danio rerio.
Macropodus opercularis — Macropodus opercularis.
Barbus candens — Tanichthys albonubes.
Puntius sachsii — Pethia conchonius.
Puntius lateristriga — Puntius denisonii.
Pethia gelius — Puntius semifasciolatus.
Hyphessobrycon anisitsi — Hyphessobrycon igneus.
Melanotaenia monticola — Chilatherina campsi.
Aquarium fish compatibility. Biological and behavioral compatibility.
Brackish water aquarium. List of fish and plants for a brackish water aquarium. 
