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Coldwater fish live at room temperature and do not need a heater, as long as the room stays within a reasonable range, roughly 60-75 °F (16-24 °C). That does not mean they are easier, or that they can live in a bowl.
- Common and comet goldfish: grow to 8-12 inches (20-30 cm) or more and live for well over a decade. They are best in a pond or a very large tank, not a typical home aquarium.
- Fancy goldfish (oranda, ranchu, telescope): slower swimmers that suit large aquariums of 30-40 gallons (120-150 L) for a pair, with strong filtration and no fast tank mates.
- White cloud mountain minnows: small schooling fish for unheated tanks of 15 gallons (60 L) or more.
- Medaka (ricefish): peaceful, hardy and great for small coldwater setups or summer patio containers.
Goldfish produce a lot of waste. They need a filter turning over the volume many times per hour and regular large water changes. Goldfish bowls without filtration are not acceptable.
Do not mix goldfish with tropical fish: their temperature needs and appetites do not match. And never release goldfish into lakes or rivers, where they become invasive.
Setting up the tank? Read our guide on how to set up a coldwater aquarium. Looking for every species that lives without a heater, from any group? See the list of coldwater fish that do not need a heater.
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 |
 Comet goldfish Carassius auratus | 79 gal (300 L) | 7.9 in (20 cm) | 50–75 °F (10–24 °C) | Easy |
 Lionhead goldfish (ranchu) Carassius auratus | 32 gal (120 L) | 5.9 in (15 cm) | 59–75 °F (15–24 °C) | Moderate |
 Medaka (Japanese ricefish) Oryzias latipes | 11 gal (40 L) | 1.4 in (3.5 cm) | 50–79 °F (10–26 °C) | Easy |
 Telescope goldfish Carassius auratus | 32 gal (120 L) | 5.9 in (15 cm) | 59–75 °F (15–24 °C) | Moderate |
 White cloud mountain minnow Tanichthys albonubes | 16 gal (60 L) | 1.6 in (4 cm) | 57–72 °F (14–22 °C) | Easy |
No species match those filters.