What sorts of fish can live in an outside pond?
There are around a dozen species of outside pond fish that suit the UK climate year-round and are legal to be kept in our ponds.
Of all pond fish, common goldfish and goldfish varieties like shubunkins and Sarasa comets are the best pond fish for most outdoor ponds because they are cheap, hardy, colourful and don’t grow too large. They are safe with aquatic plants too and should leave your pond plants alone.
They may even breed in the right conditions. Goldfish are a good choice for a small pond or even a sunken bath tub. But avoid fat, twin tailed fancy goldfish. See below.
If you have a large pond then large fish Koi Carp and Golden Orfe are suitable too and will reward you with rapid growth and greedy feeding from the surface.
How to keep koi
If you want to add Koi fish to your garden pond then debate rages on just what size pond fish like koi need, but all varieties of Koi carp including Ghost koi, and wild type carp like Common carp and Mirror carp all grow very large and need ponds measured in thousands of gallons (tens of thousands of litres,) long term. If the koi pond is more like a lake then planting is all they need to manage water quality, but if you want clear water to view them year-round, and quite a few koi, you’ll need large, powerful filtration.
Apart from being greedy feeders koi fish and other carp are well-behaved fish that will mix with any other pond fish.
British native freshwater fish
You may see native species for sale, and some are suitable for garden ponds. Gudgeon, Barbel, Rudd, Roach, Bream, and Tench are all available, with Rudd and Tench being available in a golden form. The advantage of a bright orange Golden tench is that you are more likely to see these secretive bottom dwellers, but it also makes it more visible to predators like Herons.
Rudd and Tench are the most suited to a medium or large pond size although they should have well-filtered water and deep enough ponds to keep them cool during the hot summer months. Gudgeon and Barbel really need fast-flowing, well-oxygenated water like the rivers they come from.
Avoid Trout as they are predatory, jump out and need really clean water, Perch and Chub as they are predators too. Sticklebacks are a novelty small fish that won’t eat pond pellets or dry foods so are best suited to a wildlife pond on their own. They are good mosquito larvae control in otherwise fishless ponds however.
All British native fish species may carry diseases so don’t take from the wild, inspect, medicate and quarantine before adding them to your outdoor pond. They also need a cool water temperature year-round. Pond owners must never remove fish from the wild. It's illegal.
Illegal cold water fish in the UK
Although legal to be sold in the past, some species of fish that could live in our goldfish ponds and koi ponds are prohibited from being sold and kept. These include North American Sunfish like the Pumpkinseed, Lepomis gibbosus. This is because they are an invasive species and could wreak havoc if released into native waterways. Never release fish into the wild.
Suitable pond fish species
- Sarasa Comet
- Koi carp
- Ghost koi
- Common carp
- Mirror carp
- Golden Orfe
- Blue Orfe
- Green Tench
- Golden Tench
- Golden Rudd
- Grass carp (often added for weed control)
Avoid these fish types in outdoor ponds
- Trout (predatory, jump out)
- Perch (predatory)
- Pike (predatory, grow huge)
- Eels (predatory, escape, endangered)
- Wels catfish (predatory, Grow huge)
- Zander (predatory)
- Chub (predatory)
- Sunfish (banned)
- Fancy goldfish (too sensitive, poor swimmers, not hardy)
- Tropical fish (won't survive the winter)
- Weather loach (threat to native species)
Quarantine all new purchases to keep your existing pond fish healthy.