Cold-water fish: the complete list for ponds (and aquariums), with their temperature ranges and requirements
Cold-water fish are contrasted with tropical fish, which need water heated to around 24 to 28°C all year round. Cold-water fish, on the other hand, naturally live in waters that cool significantly in winter. They are the only fish capable of living year-round in a garden pond in our climate, without heating. But “cold water” does not mean “any water”: each species has its limits and requirements.
— The short answer
The main cold-water fish for ponds are goldfish and their varieties (comet, shubunkin), koi carp, ide, tench, rudd, minnow, stickleback and, in large, highly oxygenated ponds, sterlet sturgeon. All tolerate water close to 4°C in winter, provided the pond is deep enough not to freeze to the bottom. In summer, their real danger is water that is too warm and low in oxygen.
What “cold water” means for a fish
Fish do not regulate their temperature: their bodies are at the temperature of the water. As the water cools, their metabolism slows down, they eat less, move less and gather at the bottom. A cold-water fish is simply a species whose body can tolerate this slowdown for months, then start up again in spring. A tropical fish, on the other hand, becomes weak and dies as soon as the water remains below 18 to 20°C for an extended period.
At the bottom of a sufficiently deep pond, the water remains around 4°C even when the surface freezes, because water is densest at this temperature. Cold-water fish spend the winter in this layer.
Cold-water fish for ponds
| Fish | Adult size | Recommended pond | Good to know |
|---|---|---|---|
| Goldfish, comet, shubunkin | 15 to 30 cm | From 1,000 l | Very hardy, reproduces easily |
| Koi carp | 50 to 80 cm | From 10,000 l, 1.2 m deep | Extensive filtration essential |
| Ide (orfe) | 40 cm and more | Large pond | Lives in schools, requires plenty of oxygen |
| Tench | 25 to 40 cm | From 3,000 l | Native, discreet, lives at the bottom |
| Rudd | 20 to 30 cm | From 3,000 l | Native species, red fins, lives near the surface |
| Minnow | 6 to 10 cm | Small, well-oxygenated pond | Schooling fish that likes current and cool water |
| Stickleback | 5 to 8 cm | Small natural pond | Native species; the male builds a nest |
| Sterlet sturgeon | 60 cm to 1 m | Very large pond | Very demanding in oxygen, specific diet |
The real danger: heat, not cold
Paradoxically, cold-water fish losses occur more often in summer than in winter. The warmer the water, the less oxygen it contains, even as fish consume more of it. At 25 °C, saturated water contains significantly less oxygen than at 10 °C. Add a stormy night, during which plants and algae also consume oxygen, and the pond can deteriorate within a few hours. Fish gasping at the surface early in the morning are the warning sign.
The most sensitive species are those from fast-flowing waters: minnows, ide, sturgeon and, even more so, trout. For them, an aerator running continuously during hot spells is not a luxury.
Oase AquaOxy 1000
Complete, silent aeration kit for heavily stocked ponds of 5 to 10 m³. Direct price and immediate add-to-cart:
Getting through winter
- A deep area: at least 80 cm for small species, and more than one metre for koi.
- A hole in the ice to allow gases produced by decomposition to escape. Never break the ice with a hammer: the shock waves stress the fish.
- Feed less when the water drops below 10 °C, using easily digestible food, then stop at around 6 to 8 °C.
- Do not disturb the bottom: the fish are resting there.
Hikari Wheat-Germ Medium 500 g
Wheat-germ-based food, highly digestible when the water cools. Direct price and immediate add-to-cart:
What about in an aquarium?
Some cold-water fish also live in unheated aquariums. The goldfish is the best known, but it grows large and requires a very spacious aquarium with good filtration: bowls should be avoided. The Chinese white cloud mountain minnow, a small schooling fish native to the mountains of southern China, is an excellent alternative for a freshwater aquarium at room temperature. In all cases, a cold-water aquarium should be kept out of direct sunlight to prevent overheating in summer.
Create a balanced population
Mix species according to their habitat zone: surface fish such as rudd or ide, open-water fish such as goldfish, and a bottom-dwelling fish such as tench. Avoid pairing large, voracious fish with very small species, which would end up on the menu. Always choose farm-raised fish: taking wild fish from a waterway is prohibited or regulated, and it is the best way to introduce diseases.
Aquanet 2 protective net - Oase
4 x 8 m net with poles to protect your fish from herons. Live price and immediate add-to-cart:
Aerators, seasonal food and protective nets: everything for your cold-water fish is available at Foudebassin. And to choose your fish, visit Aquiflor in Nodebais.
Frequently asked questions
— Which cold-water fish is easiest to keep?
The common goldfish or the shubunkin. Very hardy, they adapt to most garden ponds.
— At what temperature should you start to worry in summer?
Above around 25 °C, monitor oxygen levels: continuous aeration, shade and gradual additions of fresh water.
— Can cold-water fish remain under the ice?
Yes, for several weeks, if the pond is deep enough and an opening allows gas exchange.
— Can tropical fish be kept in a pond during summer?
This is not recommended: cool nights and temperature fluctuations quickly weaken them.
In summary
- Goldfish, koi, ide, tench, rudd, minnows, sticklebacks and sturgeons are cold-water fish.
- In winter, they rest at the bottom at around 4 °C in a sufficiently deep pond.
- The real risk is summer: warm water with low oxygen levels.
- Adapt the species to the pond's volume and protect them from herons.
Sources and references
- Kottelat M. and Freyhof J., Handbook of European Freshwater Fishes, 2007
- Wetzel R.G., Limnology: Lake and River Ecosystems, 3rd edition, Academic Press, 2001
- Aquiflor / Foudebassin consulting experience, Nodebais (Belgium)
Last updated: September 28, 2026.
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