Cold-water aquarium fish
10 species from the AquaLog care guide · Updated
In short: Goldfish, white cloud mountain minnows and a few barbs and danios tolerate cooler water, with ranges starting at 18 °C or lower. Whether you can skip a heater depends on your room staying inside the species' range all year, day and night.
Every species below has a temperature range in the AquaLog care guide that starts at 18 °C (64 °F) or lower. That makes them candidates for a cooler room or an unheated tank, but read the whole range, not just the bottom of it.
Do these fish need a heater?
Only if your room drifts outside their range. A tank in a room that drops to 14 °C on winter nights is too cold for most of these fish; one that holds 20–24 °C year-round may need no heater. A thermometer in the tank answers the question better than a label.
The species
| Species | Min. tank | Temperature | pH | Temperament | Group | Care level |
|---|---|---|---|---|---|---|
| White cloud mountain minnowTanichthys albonubes | 45 L (12 gal) | 16–24 °C | 6–8 | Peaceful | 8+ | Beginner |
| Zebra danioDanio rerio | 60 L (16 gal) | 18–26 °C | 6–8 | Peaceful | 6+ | Beginner |
| Peppered corydorasCorydoras paleatus | 75 L (20 gal) | 18–26 °C | 6–8 | Peaceful | 6+ | Beginner |
| Paradise fishMacropodus opercularis | 90 L (24 gal) | 16–26 °C | 6–8 | Aggressive | 1 | Intermediate |
| Gold barbBarbodes semifasciolatus | 110 L (29 gal) | 18–26 °C | 6–8 | Peaceful | 6+ | Beginner |
| Rosy barbPethia conchonius | 110 L (29 gal) | 18–25 °C | 6–7.8 | Peaceful | 6+ | Beginner |
| Buenos Aires tetraHyphessobrycon anisitsi | 150 L (40 gal) | 18–28 °C | 6–8 | Semi-aggressive | 6+ | Beginner |
| Fancy goldfishCarassius auratus | 150 L (40 gal) | 16–23 °C | 7–8.4 | Peaceful | 2+ | Intermediate |
| Denison barbSahyadria denisonii | 300 L (79 gal) | 18–25 °C | 6.5–7.8 | Peaceful | 6+ | Intermediate |
| KoiCyprinus rubrofuscus | 3800 L (1004 gal) | 4–28 °C | 7–8.5 | Peaceful | 4+ | Intermediate |
Goldfish need their own tank
Fancy goldfish prefer cooler water than tropical fish, grow large and produce a lot of waste. Keep them with other fancy goldfish, not with tropical species. Koi are pond fish.
Temperate species still have upper limits
Several fish here, such as the white cloud mountain minnow, prefer it cool and struggle in very warm water. In hot climates, check the top of each range too. See fish that tolerate warm water.