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Do Koi Fish Get Along with Goldfish?

Can you tell the difference between koi fish and goldfish? Though they may look alike, they’re not the same and usually require separate care and attention. If you’re considering keeping either (or both) species as pets in the same aquatic environment, then you may be wondering if they can survive together and live compatibly? Well, the answer is…

Yes, koi fish and goldfish can live together peacefully in captivity, provided they’re the same size and kept in a very big tank or outdoor pond. Since both species are peaceful in nature, grow quite large and need plenty of space to swim, forage and explore, they’ll get along much better if they’re not crowded or overpopulated.

Now that you know you can easily keep koi fish with goldfish in the same aquatic environment, let’s explore this topic further and in more detail. I’ll explain the kind of water conditions they require, the types of foods they eat, and whether or not they can crossbreed. I’ll also discuss their temperaments, breeding habits, and potential tank or pond mates for both species.

So, if you’re ready to dive deeper into the (shared) aquatic world of both the koi fish and the goldfish, then let’s begin!

Are Koi Fish Compatible with Goldfish?

Koi fish and goldfish are compatible under the right circumstances. If you plan to keep them together in the same tank or pond, then they must be of similar size otherwise the smaller ones may get eaten! Both species are opportunistic feeders with voracious appetites and will dine on anything that fits into their mouths, including other fish!

Koi fish and goldfish are both docile in nature but can become aggressive if kept in too small of a tank or an overpopulated pond. As well, they may eat each other’s eggs or offspring if not fed often or enough. Koi fish have been known to bully certain types of goldfish, namely the fancy ones, so it’s better to keep them with the bigger types like orandas or shubunkins.

Will Koi Fish and Goldfish Fight?

It’s highly unlikely for koi fish and goldfish to fight each other – since both are known for their calm demeanor and easy to care for nature. However, aggression levels in koi fish especially will escalate under stress. Poor water conditions, a crowded tank or pond, lack of food, and spawning behaviors are all possible culprits for heightened tension.

To reduce stress and hostility in both koi fish and goldfish, begin by testing the water parameters – particularly the pH and ammonia levels. As well, avoid overpopulating the tank or pond, ensure you’re feeding your fish adequately and don’t keep more males than females, if at all possible. A clean, stable aquatic environment is the key to a healthy, peaceful aquarium community.

Are Koi Fish Aggressive Towards Goldfish?

Koi fish are rarely aggressive towards goldfish, unless they’re in a cramped aquarium or overpopulated pond. If the water parameters are ‘off’, then koi fish may become stressed. This, in turn, can then lead to increased tension among tankmates. As well, smaller goldfish can sometimes be the target of koi fish bullying which is why you should only keep fish of like size together.

Conversely, a male goldfish that mistakes a female koi fish for a breeding companion may become more aggressive by chasing her around the tank and nipping at her fins. This inadvertent behavior isn’t usually cause for concern and should subside once the mating season has ended. Should it continue, however, you may need to isolate the aggressor.

Oranda goldfish

Do Koi Fish and Goldfish Like the Same Water Conditions?

Since koi fish and goldfish are both types of cold-water carp, they can survive in low temperatures but prefer a range somewhere between 82-and 90-degrees Fahrenheit. A stable pH around 7.2 to 7.5 is best although they can tolerate a slightly lower (6.5) or higher (8.0) level. As both species are big and like to forage, a large aquatic environment (250- to 1,000-gallon pond) is recommended.

Do Koi Fish and Goldfish Eat the Same Food?

Koi fish and goldfish generally eat the same kinds of food. Since both are a species of carp fish, they’ll feast on just about anything organic including krill, plankton, and vegetables – even breakfast cereal and dead leaves. The general rule is if it can fit into its mouth, then it’s fair game! For this reason, you don’t want to keep either species with small fish or eggs/offspring as they’re likely to be eaten.

Can Koi Fish and Goldfish Breed Together?

Yes, koi fish and goldfish can crossbreed since both are a type of carp fish. They can spawn with one another and reproduce, especially when kept together in the same tank or pond. Come fall, which is typically the breeding season for both species, you may notice little hybrid offspring of your koi and goldfish swimming about!

Do Koi Fish Eat Goldfish Eggs?

Koi fish will eat goldfish eggs – and their own eggs, for that matter! Koi fish are omnivorous and eat a variety of both plant- and meat-based foods. They’ll even eat other fish as well if they’re small enough to fit into their mouths. Therefore, if you intend to breed koi fish, you must keep them in a large, heavily planted pond which will provide cover for eggs and hatchlings.

Do Goldfish Eat Koi Fish Eggs?

Goldfish, like koi fish, are omnivores and will eat both plant- and meat-based foods, including other fish eggs. As opportunistic feeders, they forage constantly throughout the day looking for edibles to munch on. Their insatiable appetites and willingness to eat just about anything that can fit into their mouths (including other fish), makes them a threat to newly hatched offspring.

goldfish eggs

What Fish are Compatible with Koi Fish?

The best tank or pond mates for koi fish are undoubtedly the goldfish. The best types include comets, orandas, and shubunkins. Apart from that, barbs, catfish, loaches, plecos, and tenches can also dwell peacefully with koi fish. Be sure whatever fish you choose is of similar size and temperament, doesn’t require more care than a koi fish, and won’t compete with koi fish for food.

What Fish are Compatible with Goldfish?

The most compatible tank or pond mates for goldfish are often koi fish. However, since goldfish are docile and easy to maintain, other species of aquarium fish like barbs, loaches, plecos, catfish and ricefish will do well in the same aquatic environment. When choosing goldfish companions, ensure they’re of like size and temperament, prefer the same water conditions, and eat the same types of food.


To summarize, koi fish and goldfish generally get along well in captivity, provided they’re of similar size and living in a large aquatic environment. Since both species grow big and need a lot of space to swim, forage and explore, they’ll dwell peacefully together in a large tank or outdoor pond. Just make sure the water parameters are stable and the area is overpopulated.

I trust this article has provided you with the information you seek regarding the co-habitation of koi fish and goldfish. Thanks for reading and good luck with your aquarium hobby.

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