Can Goldfish And Koi Live Together? (Tips For Success)

Betta ebook-ban

Last Updated on 2023-05-24

If you’re a fish owner, you may be wondering whether goldfish and koi can live together. After all, koi are able to grow up to 3 feet in length (in extreme cases), whereas goldfish will barely make it past a foot. In this article, you’ll learn the best ways to help koi and goldfish live together peacefully, and more importantly, if it’s even worth doing!

First Of All, Can Goldfish And Koi Live Together?

Keeping goldfish and koi together is possible; however, there are some precautions that you’ll need to follow. You need to make sure that they’re roughly the same size and be aware that if either has eggs or fry, they will be eaten.

In some cases (especially with goldfish), when one fish is smaller than the other, they may be eaten as well. This is why you need to make sure both fish are roughly the same size. This is not because either fish are aggressive, but because they’ll eat whatever can fit in their mouths.

Can Goldfish And Koi Live Together In A Tank?

You should not keep goldfish and koi in a tank together permanently; however, it can be done temporarily, and only when the koi aren’t fully grown.

Koi can grow up to 3 feet in length, so the vast majority of tanks aren’t going to be suitable for them. In fact, it’s only commercial tanks that they can live happily in. If you’re going to keep koi in a tank, then you should only do it until they’re about 6″ in size. At that point, they’ll need to be moved to a pond.

Goldfish, on the other hand, as you know, already can live happily in tanks that are 30 gallons in size (with an extra 10 gallons for each additional goldfish.)

And lastly, if you do plan on keeping small koi in a tank temporarily, you should make sure that the tank is 50 gallons or bigger.

Related Articles:

How To Setup A Pond For Koi And Goldfish

If you’re going to keep koi and goldfish in a pond together, then you need to make sure you’re setting it up properly! Here’s everything you need to know!

Pond Size

When you’re setting up a pond, the first thing you need to consider is the size. Koi need ponds that are at least 1000 gallons in size, with some areas of the pond being 3-4 feet deep. You need this depth to help them overwinter, as the water in the deeper parts will be warmer.

The reason that the pond needs to be so big is that koi are social fish, and each one needs about 200-300 gallons of space to stay happy. You should also be keeping a minimum of three together, although more is better.

If possible, you want the pond to be about 6-8 feet across, so they have ample room to swim. Remember, koi prefer to swim horizontally over vertically, so they need lots of room to swim this way.

And because goldfish are a lot smaller, if your pond is big enough for your koi, then it’s going to be big enough for your goldfish as well! (Each goldfish will need about 50 gallons each.)

pH Level

You need to keep an eye on the pH as well. If it’s too high or too low, it could begin to burn your fish’ skin and cause internal damage too. The ideal pH for koi and goldfish is around 7.2-7.5. However, they can easily survive in a pH range between 6.5-8.

When trying to keep your pH levels stable, you may need to perform more water changes than if you’re adding your fish to an older pond.


One big problem you may have when keeping goldfish and koi together is finding the right plants. While goldfish are fine with pretty much all plants, koi are known to be destructive. When you’re adding plants to your pond, you should think about adding periphery plants rather than having plants throughout the pond.

If you want plants in the middle then try adding sturdy plants such as water hyacinth, water smartweed, and water lettuce! You can also add duckweed, but be warned, if you add duckweed to your pond, you will need to scoop out large parts of it every so often.

Feeding Your Fish

Koi and goldfish are both omnivores, so feeding them isn’t that difficult. You just need to make sure that you’re putting enough food in the pond for them both.

When you’re thinking about food, the first thing you want is a high-quality flake for both fish. If you’re not sure which fish food to get then, I’d recommend TetraPond Variety Blend Fish Food.

As well as this, you should also make sure you’re adding live food to the pond every once in a while. Not only is this a great source of nutrients for them, but it’s also going to be a lot more fun as they’ll feel like hunters. Not to mention, it stops their diet from becoming boring.

But it’s not just live food; you should be feeding them either. You should also try adding blanched vegetables to the pond to make sure they’re getting enough fiber. (They’ll also get some of this from eating plants too!)

Koi carp (11) - PICRYL Public Domain Image

Can Koi And Goldfish Eat The Same Food?

To answer the question, YES!

Koi can eat goldfish food, and goldfish can eat koi food. Both fish are carp, and as long as you’re feeding them high-quality food, it doesn’t matter whether it’s branded as goldfish food or Karp food.


One of the most important things when putting any two fish together is the temperament of both fish. While koi and goldfish are generally peaceful fish, there are some problems you may run into when housing them in the same pond.

The biggest worry is that if one is bigger than the other, the smaller one may end up being eaten. Because of this, you want to make sure that the fish you’re adding to the pond are all roughly the same size.

Apart from the size difference, there isn’t much more you need to worry about. Both koi and goldfish are rarely aggressive, and the chances of them fighting or killing each other are actually pretty slim.

So as long as they’re roughly the same size, you don’t have anything to worry about!

betta care facebook group


Most people don’t think about whether their fish will breed or not when they’re being added to the pond. But if your fish are breeding too much, then you may end up overstocking your pond (if the infants survive to adulthood).

If breeding is going to occur, it’s more likely that your goldfish are going to breed with each other as they’re known to. And if they do breed too much, they can birth 100’s of fry in a year.

It’s also possible for your goldfish and koi to breed with each other; however, the fry that comes from this will be sterile. If you’re keeping fancy goldfish or koi and you want to keep them as pure as possible, it may be a good idea not to mix them.

Fortunately, though, even if your goldfish do breed, a lot of the fry will probably be eaten before any make it to adulthood.

Articles You May Like:

What You’ll Need To Do Each Season

As the seasons change, you may need to change how you look after your pond. Here’s what to do during each season to make sure you give your fish the best chance of survival.


During winter, you’ll need to do quite a bit of maintenance to ensure the survival of your fish. First of all, double-check your pond heaters to make sure they’re working properly.

As well as this, you should also make sure you’re trimming your plants, especially plants that haven’t been doing so well. If they die in the winter, then they’re going to release ammonia into the water.

In winter, you’ll need to reduce the amount that you’re feeding them as they’ll no longer be eating as much. However, before winter, try to feed them as much as possible while they’re still eating so they can bulk as much as they can.


During the spring and summer, the most important thing you can do is make sure you’re feeding your fish more. You should be feeding them high-quality fish food with loads of protein to make sure they’re eating enough.

This is important as it’s going to help them grow stronger and increase their chances of survival when they’re overwintering.

Once, again you’ll need to keep an eye on your plants to make sure they’re not growing too much. On top of this, there’s going to be an increase in potential pests in the water, so keep an eye on that too.

You may also need to keep an eye on the oxygen levels of the pond as well. Warm water can’t hold as much oxygen as cold water, so if there’s a problem, add more aeration for your fish’ survival.


Now you know everything there is to know about keeping goldfish and koi together! While they can live together temporarily in a tank (if they’re small), you’re much better off keeping them together in a pond for long-term health.

If you liked this article, make sure you check out the rest of the website. Otherwise, have a great day!

Ultimate Betta Fish Care Guide
About the author

Hey! I'm Nicolas from Iguane Media !

Blogger and Owner of the betta care fish guide
Thanks for reading this blog

I'm an Animal Lover