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This list shows every fish in our database marked as coldwater: species that live comfortably at room temperature without a heater, roughly 60-75 °F (16-24 °C). It is generated automatically from our species data.
"No heater" is not the same as "no equipment". Coldwater fish still need a cycled tank with a filter, and goldfish in particular need oversized filtration and frequent water changes because they produce a lot of waste. A goldfish bowl without a filter is not an acceptable home for any fish.
- Common and comet goldfish grow large and are best in ponds or very large tanks.
- Fancy goldfish suit big aquariums with calm water and no fast tank mates.
- White cloud minnows and medaka are small, peaceful and perfect for unheated tanks of 15 gallons (60 L) or more.
Room temperature varies a lot: in summer an unheated tank can overheat, and in a cold basement it can drop too far even for coldwater fish. Keep a thermometer in the tank and avoid placing it near windows or radiators.
Do not mix goldfish with tropical fish, and never release coldwater fish into lakes, rivers or ponds connected to natural waters.
Setting up the tank? Our coldwater aquarium guide covers tank size, filtration and plants.
Profiles of goldfish and their fancy varieties, white cloud minnows and medaka are grouped under coldwater fish.
Coldwater fish
| Species | Min. liters | Size | Temp. | Difficulty |
|---|---|---|---|---|
 Common goldfish Carassius auratus | 79 gal (300 L) | 7.9 in (20 cm) | 50–75 °F (10–24 °C) | Easy |
 Oranda goldfish Carassius auratus | 40 gal (150 L) | 7.1 in (18 cm) | 59–75 °F (15–24 °C) | Moderate |
 Lionhead goldfish (ranchu) Carassius auratus | 32 gal (120 L) | 5.9 in (15 cm) | 59–75 °F (15–24 °C) | Moderate |
 Comet goldfish Carassius auratus | 79 gal (300 L) | 7.9 in (20 cm) | 50–75 °F (10–24 °C) | Easy |
 Dojo loach Misgurnus anguillicaudatus | 53 gal (200 L) | 7.9 in (20 cm) | 50–75 °F (10–24 °C) | Easy |
 Medaka (Japanese ricefish) Oryzias latipes | 11 gal (40 L) | 1.4 in (3.5 cm) | 50–79 °F (10–26 °C) | Easy |
 White cloud mountain minnow Tanichthys albonubes | 16 gal (60 L) | 1.6 in (4 cm) | 57–72 °F (14–22 °C) | Easy |
 Paradise fish Macropodus opercularis | 21 gal (80 L) | 3.5 in (9 cm) | 61–79 °F (16–26 °C) | Easy |
 Telescope goldfish Carassius auratus | 32 gal (120 L) | 5.9 in (15 cm) | 59–75 °F (15–24 °C) | Moderate |
No species match those filters.
Frequently asked questions
Can goldfish live without a heater?
Yes, goldfish are coldwater fish and do well at room temperature. They do need a large tank, a strong filter and regular water changes.
Can a betta live without a heater?
No. Bettas are tropical fish that need about 78-80 °F (25-27 °C); in most homes that requires a heater.
What is the best small coldwater fish?
White cloud mountain minnows and medaka stay small, are peaceful and live well in unheated tanks of about 15 gallons (60 L).
