Koi are non-aggressive fish and can live in harmony with other freshwater dwellers. Plenty of great choices exist if you are thinking about adding variety to your pond and want something that won’t threaten or overshadow your koi.
The following suggestions are compatible with koi, but not necessarily with each other. If you plan to add multiple species to the pond, make sure all your additions get along as well. Don’t underestimate the power of the food chain when you are mixing and matching several types of fish and wildlife.
Goldfish are natural friends of koi as they both are part of the carp family. Koi and goldfish share the same water condition needs and adapt similarly to weather. If you decide to combine the two, you might need to increase the power of your filtration system as goldfish and koi are true relatives when it comes to producing waste–a lot of it.
Two classes of goldfish exist: pond goldfish and fancy goldfish. As the name implies, pond goldfish are well suited for pond life. While these fish are often packed into tanks at the local pet store or sold at fairs and carnivals, they actually require much more space than an aquarium can provide. In fact, pond goldfish can reach sizes from 12 to 14 inches in the right conditions.
Fancy goldfish come in a variety of shapes, colors, and fin types. They are less hardy than pond goldfish and don’t acclimate to the cold as well, so they are most appropriate for climates that don’t get freezing weather. They will also grow relative to the size of their environment but are smaller than pond goldfish. Fancy goldfish come in a range of varieties and prices.
If you are seeking to spark friendships within your pond, golden orfe are a great option. These social fish prefer to be in groups to the point that they can die from loneliness if isolated for too long. Plus, they like to hang out near the top of the water, so they are highly visible almost all the time and are known to coax other fish to the surface with them.
Golden Orfe generally are bright orange or golden in color and can grow to around two feet long. They are hardy fish that can adapt to a broad range of temperatures, which makes them great koi companions for ponds in almost all climate zones. These non-aggressive fish will get along well with mature koi, but should not be kept with smaller fish as they are likely to eat them.
Chinese Hi Fin Banded Shark
You might be surprised to learn that a shark could be friendly and get along swimmingly with its pond mates. That’s because the Chinese Hi Fin Banded Shark is actually a species of fish. It makes for a good bottom-feeder that can coexist with koi and help clean up the pond by eating algae.
This not-so-shark “shark” will come to the surface for mealtime and will happily eat koi pellets. Just make sure that you have a large enough pond, because these fish can grow to be a similar size as koi and, in some cases, even larger. While Chinese Hi Fin Banded Sharks are suitable for cold water, they can’t adapt to freezing temperatures and will need to be moved inside when the outdoor temperature drops below 40°F or the water temperature drops below 55°F.
Japanese Trapdoor Snail
Another algae eater that is able to endure colder weather is the Japanese Trapdoor Snail. This type of snail bears no relation to the ones you spot outdoors in the rain. This species of snail can grow to the size of a golf ball or a bit larger. They have a hardy nature and the ability to live in various climates, but they thrive in water temperatures between 68°F and 85°F.
Japanese Trapdoor Snails are great additions to your pond because they will eat all the dead stuff that other pond dwellers won’t or can’t. Plus, they won’t harm your live plants. However, remember that snails can only consume small amounts of waste relative to what koi can produce, so you will still need to clean.
Rosy Red Minnows
Rosy Reds are peaceful companions that are easy to care for, which makes them great additions to your koi pond. They are exceptionally tolerant of temperature changes and flexible enough with their diets that they will be able to eat the same food as your koi.
Rosy Reds, which aren’t actually red but more of an orange hue that varies over time, are incredibly active fish, and you will often see them swimming in the winter, even below a layer of ice. Unfortunately, the life expectancy for these fish is only about two to four years, so your koi will long outlive them.
Rosy Reds often are used as feeder fish and can come from overcrowded tanks that make them more likely to carry diseases. It’s important that you secure yours from a reputable source and follow quarantine protocols.
Mosquitofish are relatives of the guppy, and with a drab, grayish color, they will not come close to stealing the show from your koi. However, they’re incredibly hardy and can tolerate a wide variety of temperatures and water conditions.
As their name suggests, Mosquitofish dine voraciously on mosquitos and have been used in pest-control programs for decades. These fish also eat beetles, mayflies, mites, and other insects that can damage pond plants. They will even at times hang out with your bottom-dwellers and eat algae–Mosquitofish really love to eat. These tiny but active fish will work to keep your pond healthy.
Frogs are another great non-fish addition to a pond environment. Like Mosquitofish, frogs are excellent at keeping the insect population down. In fact, they can eat up to 10,000 insects in one summer season. Their favorite insects are flies and mosquitos, and because they will also explore beyond the pond, they’re also beneficial for managing insect populations in other areas of your yard. If you have a garden, then pond frogs can be a valuable ally.
Although it is possible to purchase tadpoles to home grow, most pond owners advise attracting frogs to your pond rather than purchasing them. Your cute little tadpoles could be a non-native species or may carry diseases that harm your pond, and your koi will probably eat them. Purchasing an adult frog is not a much safer bet, because it will decide for itself whether it wants to live with you or go elsewhere.
Sturgeon is another family of fish that mingles well with koi. These large fish can grow up to several feet and should not be kept in ponds that are below one thousand gallons of water or in ponds with a lot of fish. Sturgeons do well in the winter, but they are not adaptable to areas that experience intense summer heat.
A lot of available information suggests that catfish and koi are potentially a fine match; however, a lot of information also exists about problems that can arise from keeping catfish in your koi pond.
Catfish are somewhat aggressive, and they can pose a danger to your koi if they get big enough. You can keep a small-mouth species with koi, such as channel catfish, but avoid large-mouth catfish, such as redtail catfish, as they can eat a fish their own size or even a bit larger.
Additionally, though they are bottom feeders, catfish will not help to keep your pond clean. In fact, they can actually contribute to worsening the water quality by stirring up sediment on the bottom of the pond. Add just one or two catfish if you are keen on this option.
Creating a vibrant and diverse environment in your koi pond means choosing aquatic companions that can coexist harmoniously within the ecosystem of your pond. Whichever you choose, always be sure to purchase from reputable sources and follow standard quarantine guidelines.