Can Guppies and Koi Live Together?

If you’re even slightly versed in the art of fish keeping, you probably already have the answer to today’s question. There’s no way Koi fish and guppies can live together in peace without the latter falling victims to Koi’s sheer size and appetite, right?

Well, you’re right for the most part. But hear me out.

I would never recommend guppies as ideal tank mates for the Koi, but I have to tackle the topic seeing how many people are interested in it. And with so many stories and anecdotes making some interesting claims on the topic, I had to jump in.

So, is there some truth to this claim that Koi fish can coexist with guppies? Let’s have a look!

Do Guppies and Koi Get Along?

The simplest answer is no for several reasons. First, Koi can grow quite large and need a lot of space. The normal tank and pond Koi fish can grow around 10-12-14 inches depending on the environmental conditions, diet, and genetic predisposition. However, other Koi species can achieve monstrous proportions of up to 36 inches.

They are also omnivorous and display some occasional predatorial behavior, especially when paired with small fish species. Like, I don’t know, guppies, for instance. In this context, can you accommodate guppies and Koi fish in the same environment?

Actually, there is, so long as you consider several cautionary strategies along the way:

– Size of Koi Fish

There’s an unwritten rule in the wild saying that large fish will consume the smaller ones. This stays true pretty much regardless of the fish’s species unless the fish is herbivorous and consumes plants exclusively. Other than that, a larger fish will always see the smaller one as food.

To minimize this risk in the case of the Koi/guppy dynamic, consider choosing a smaller Koi species. Preferably one that doesn’t grow over 12 inches. This means avoiding Japanese species automatically since these Koi will usually grow up to 20 inches. A 10-12-inch Koi should pose fewer risks to your guppies, although the fish’s size alone isn’t enough to keep guppies safe. This is where the following 2 tips come in to complete the accommodation strategy.

– Use Lots of Plants

The more tank plants you have, the lower the risks of your Koi interacting with guppies aggressively. Fish don’t have great attention spans, so breaking the line of sight between aggressors and victims will usually calm things down fast. Plants are a good way to create barriers between the fish, allowing guppies to escape the Koi’s potential aggression.

Guppies can traverse their environment faster since they’re smaller, causing the Koi to lose interest in pursuing them. It also helps keep the fish into a larger environment with plenty of room for both. The larger the tank or the pond, the more room you’ll have for plants and decorations that will serve as hiding spots for guppies.

– Feeding Koi Regularly

Koi are rather large fish coming with a fitting appetite. The problem with feeding the Koi is that their eating pattern varies depending on factors like:

  • How large they are
  • How many of them do you have
  • The Koi’s age
  • Their environmental parameters, primarily temperature
  • Their appetite, since not all Koi fish will eat the same

Based on these factors, you may need to feed your Koi once or several times per day. Some people feed the Koi up to 4 smaller meals per day to ensure a balanced intake of nutrients, but this will vary drastically. Temperature is the most relevant factor here.

The warmer the waters, the hungrier your Koi fish will get since their metabolic rates will increase accordingly. If the water is colder, the Koi will eat fewer meals, going as low as 1 meal per week. The latter usually happens in case the water temperature drops below 54 F, at which point you won’t have guppies in the Koi’s habitat anyway.

The main take-away point here is that you need to keep your Koi satiated. They’re more likely to attack your guppies if they’re hungry, especially smaller specimens.

Requirements for Guppies and Koi

There are noticeable differences between Koi and guppies in terms of water requirements. Fortunately, I think you can make it work, given some careful preparation. This includes:

  • Tank sizeGuppies require around 2 gallons of water per fish, while Koi fish may need 30 gallons per fish. This means you should invest in quite a sizeable aquarium if you plan on keeping the fish indoors. Your task will be easier for outdoor ponds since ponds can go as big as you like them. The goal is to provide both species with enough room to minimize interactions between them and prevent aggression. Having more tank or pond space will also allow you to add plants and other elements that guppies can use for hiding spots.
  • Temperature – Guppies are tropical fish and require stable temperatures between 72 and 82 F. The problem with guppies is that they aren’t that versatile when it comes to environmental temperatures. If the water temperature drops below 72, they will begin to show signs of discomfort. Fortunately, the Koi is versatile. This fish can remain comfortable at temperatures between 68 and 80 and can even survive at 90 F, although that’s too much for them. Keeping the water temperature in the mid-70s will accommodate both species. Just remember that warmer waters will stimulate the Koi’s food appetite, so you need to feed it more often
  • General water parameters – Koi fish and guppies will produce a lot of poop, so you need to clean their habitat regularly to ensure the stability of their water parameters. In this sense, both Koi and guppies have identical preferences – clean, clean, and stable waters with minimal residues and floating particles. Keep ammonia levels to 0 and perform weekly partial water changes to preserve the system’s stability.

Can Guppies Stay Outside in Koi Pond?

Yes, they can. Guppies can survive and even thrive in an outdoor pond, but they require more assistance to do so. The problem is always the temperature. Guppies cannot remain comfortable at temperatures lower than 72 °F. When that happens, they will experience lethargy, a reduced appetite, and even a weaker immune system.

So, you need to heat up the pond water to keep them comfortable. Also, you need to move guppies inside once the cold season approaches, and the outside temperatures drop. Koi fish have no problems adapting to lower temperatures, but guppies can’t.

Do Koi Fish Eat Guppies?

Koi fish aren’t exactly aggressive, and they aren’t predators at heart, but they will eat smaller fish given the opportunity. Especially if the fish are significantly smaller than the Koi, as is the case with guppies. Fortunately, as I’ve explained in today’s article, there are ways around that.

To summarize:

  • Provide the fish with sufficient space to minimize interactions between them and allow guppies to retreat in case of danger
  • Add several plants and rocks to serve as hiding spots for guppies
  • Keep the Koi fish full, since hungry Koi are dangerous Koi
  • Make sure you accommodate both species in terms of water requirements

Other than that, you should also monitor the tank dynamics regularly. If you feel like your guppies are in danger, you might want to consider separating the 2 species.


Koi aren’t exactly the dream tank mates for your guppies, so I wouldn’t recommend pairing them unless you really want to. That being said, you can accommodate them, so long as you put in the efforts necessary.

avatar Noah
I’m Noah, chief editor at VIVO Pets and the proud owner of a playful, energetic husky (Max). I’ve been a volunteer at Rex Animal Rescue for over 2 years. I love learning and writing about different animals that can be kept as pets. read more...

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