Fish That Do Not Need a Heater: Unheated Tank Species
Species that tolerate room temperature
| Species | Temperature range | Adult size | Min tank | Group |
|---|---|---|---|---|
| Cherry Shrimp | 65–78°F | 1.0″ | 5 gal | 6+ |
| Nerite Snail | 65–82°F | 1.0″ | 5 gal | single ok |
| White Cloud Mountain Minnow | 60–72°F | 1.5″ | 10 gal | 6+ |
| Amano Shrimp | 65–80°F | 2.0″ | 10 gal | 3+ |
| Mystery Snail | 68–82°F | 2.0″ | 5 gal | single ok |
| Panda Corydoras | 68–77°F | 2.0″ | 20 gal | 6+ |
| Zebra Danio | 64–77°F | 2.0″ | 10 gal | 6+ |
| Common Goldfish | 60–74°F | 10.0″ | 40 gal | single ok |
Rules for an unheated tank
Stability beats warmth. A tank sitting steadily at 68°F is far healthier than one swinging between 66 and 76°F as the central heating cycles on and off. Before committing, put a thermometer in the room and record the low and high over a week — particularly overnight in winter.
Avoid exterior walls and windows. These are where the daily swing is worst.
Bigger is more stable. A 5-gallon tank tracks room temperature almost instantly; a 29-gallon lags by hours and smooths out the peaks.
Keep a heater anyway. Not running, but on the shelf. If the house temperature drops during a cold snap or a power outage, you will want it. A heater set to the bottom of the range acts as a floor, not a thermostat.
What not to keep unheated
Anything with a minimum above about 72°F. That includes most gouramis, rams, discus, cardinal tetras and virtually all soft-water South American species. Running them cold does not kill quickly — it suppresses the immune system and they die of something else three months later.
Frequently asked questions
Can fish live without a heater?
Yes, provided the species tolerates your room temperature. 8 of the species we cover are comfortable at 68°F or below, including white cloud mountain minnows and common goldfish.
What is the best fish for an unheated tank?
White cloud mountain minnows are the classic choice: hardy, colourful, peaceful, comfortable from the low 60s to mid 70s, and small enough for a 10-gallon tank.
Is room temperature enough for a betta?
Usually not. Bettas need 76–82°F. Most homes sit below that, and cold bettas become lethargic and prone to disease.
Do goldfish need a heater?
No. Common goldfish are coldwater fish and are healthier without one. They do, however, need far more space than most people expect — a 10-inch adult needs 40 gallons or more.
Next steps
Written and reviewed by Marcus Rivera. See our methodology for how figures on this site are derived.