Do Koi Fish Bite?

Degree of Concern Varies Between Humans and Other Fish

A koi pond is often the perfect touch for landscaping a garden. It fosters tranquility and is the perfect place to enjoy a zen moment or two. If you’re new to koi, however, you might be a little trepidatious. Are you worried that koi fish may bite? 

A Child Playing with Different Koi
A Photo of a Child Happily Playing and Petting Koi Fish

No, koi fish don’t bite. But they may nibble your fingers with a pulling motion. Here we’ll explore: 

  • Are koi teeth sharp?
  • Should you put your fingers in a koi pond?
  • Can koi bite other fish?
  • Can koi eat other fish?
  • Can koi live with other kinds of fish?
  • Will koi be aggressive to goldfish?
  • Will koi attack people?
  • Can I stop my koi from bullying other fish?
  • Can you swim with koi fish?
  • Can you pet koi fish? 

Are Koi Teeth Sharp? 

No, koi teeth are certainly not sharp. They are meant only for grinding up food. While koi have teeth, they’re not the kind of teeth you’re thinking about. They’re not in the mouth but rather the back of the throat, so they’re hard to see. Koi teeth are truly minuscule, with many owners comparing them to tic tac candies. 

A Single Koi Fish with a Hook
A Carp Fish with a Hook or Tooth in its Mouth

As a koi owner, you won’t see your fish’s teeth. You may be able to hear them. However, that’s because these teeth are used when the fish grinds up food. Koi teeth are called pharyngeal teeth. The koi’s pharyngeal teeth are flat and meant specifically for grinding. 

The koi’s teeth are found immediately behind its gill chambers. They’re attached to the pharyngeal bone. When koi grind their food, they use their pharyngeal teeth as well as something called carp stone. This is a bony area situated above the pharyngeal teeth and at the top of the throat. The koi grinds its teeth against this hard section.  

Should You Put Your Fingers in a Koi Pond? 

You won’t get hurt if you put your fingers in a koi pond, but you will notice a strange sensation if the teeth mouth your teeth. I would describe it as a pulling sensation. It may even feel like suction. In most cases, this will be no more than a funny mild event. I have even grown to like it.

A Koi Fish Going Towards a Hand
A Colorful Koi Fish Attempting to Bite a Person

Koi do this to find out if your fingers are food. They’re tasting your fingers to test them out. Many koi pond owners enjoy feeding their koi by hand, and if you want to try this, there’s no need to hesitate. 

Can Koi Bite Other Fish? 

A koi trying to bite us just feels like pulling or sucking. To other fish, however, it feels very different. Although koi fish don’t have teeth in their mouths, they are remarkably strong. They use this strength to make aggression distressing to other fish. 

It’s generally around food and when eating that koi tends to be aggressive. In some circumstances, they may bully fish they perceive to be slower or weaker. 

Certain situations may lead to aggressive behavior in koi. Some of these include giving your koi incompatible companions, water quality problems in the pond, and injury or illness. 

A Group of Compressed Koi Fish Biting Each Other
A Group of Koi Fish Trying to Bite Each Other

Others are inappropriate or inadequate food, and too little space. Another reason koi may become aggressive is breeding and spawning. During breeding and spawning, male koi tend to get more aggressive overall. 

Don’t put smaller fish in the same outdoor pond with your koi. The large fish are likely to bully them, affect their quality of life, and even eat them. If they’re small enough to fit in a koi’s mouth, they’re not likely to last long and will become fish food. They may not look like it, but they can be a bit of a smart ass sometimes.

Can Koi Eat Other Fish? 

As we just touched on, yes, koi can eat other fish. Koi will often eat smaller fish, as long as they can easily fit in its mouth. As an omnivore and opportunistic eater, koi will eat pretty much anything they can. 

A Group of Koi Fish Biting Eachother
Koi Fish Biting and Feeding

That is why it is recommended to be cautious about putting small decorative items (such as rocks) in your pond, as koi might try to eat them. In stark contrast to their calm reputation, koi may even eat their own young (baby koi are known as fry). 

Can Koi Live with Other Kinds of Fish?  

As we’ve learned, you shouldn’t put fish smaller than your koi in the same pond. But are there any kinds of fish that do well in koi ponds? The most important factor is that they’re at least the same size as your koi.  If they’re larger, you must ensure they won’t be aggressive to your koi or eat them. 

Learn about their temperaments and compatibility with other fish, checking specifically for information on how they get along with koi fish. You must also ensure that your koi pond water and general environment will suit whatever species of fish you add. 

Will Koi Be Aggressive to Goldfish?

Having goldfish with koi works under some circumstances. Of course, they may be problems that we should try to avoid. If there are adverse circumstances, such as poor water or food quality, overcrowding in the pond, and general stress, our koi are more likely to bully and distress our goldfish. 

A Single Koi Fish in an Aquarium
A Photo of a Goldfish

We have to be aware there is some risk inherent in putting goldfish with koi, especially if the goldfish are smaller than the koi. There have been cases of koi targeting goldfish and trying to injure them. Experts have found they may target the goldfish’s eyes. 

One type of goldfish that most koi often live peacefully with is golden orfes. These are simply large goldfish of the common variety. In the end, Koi are no different from us, we all have our besties.

Will Koi Attack People? 

No, your koi fish cannot attack people. They don’t have teeth in their mouths but rather in the back of their throats. A human is too big for a koi to attack. Even if it managed to get your whole finger in its mouth, it wouldn’t be able to use its teeth to bite you. The koi will only be able to suck on your finger and then go on its way. 

A Photo of Someone Getting Bitten by a Koi Fish
A Koi Fish Biting a Finger

Even if a koi fish seems aggressive towards a stranger, it likely won’t be like this with you. That is after it’s become used to seeing you bring the food. Koi are smart enough to remember you and know that you feed them. 

Can I Stop My Koi from Bullying Other Fish?

While there’s never a guarantee that your koi won’t bully or harass other fish, there are certain steps you can take to make it less likely. 

One of these is ensuring there is more than enough space in the pond. If it’s too small, your fish will get stressed and more likely to lash out. Another is to quarantine any new fish for a short period of time. For example, you could separate your pond into sections. You can put your new fish in one part of the pond that the koi cannot access. During that time, your koi will get used to them being there but won’t be able to reach them.

Can You Swim with Koi Fish? 

The answer to this question depends on a variety of factors. One of these is whether the pond is big enough for you to swim in without getting in the way of your fish. Chances are your koi pond won’t be anywhere near big enough for you to actually swim in. However, if it’s a relatively large koi pond, it may be large enough for you to get in and sit down. 

A Variety of Koi Fish With Two of Them with their Mouth Open
Two Koi Fish With Their Mouth Open

If you’re going to swim or sit in a koi pond, be ready for the pulling or sucking feeling we talked about earlier. Koi are curious fish and they will come over and investigate you to see what you are. Of course, they’ll realize you’re far too big to be food as you cannot fit in their mouths. Even if they did try to bite you, they only have flat grinding teeth at the back of their throat and none in their mouth. 

Don’t harass the fish. They will touch you but you shouldn’t risk annoying them. Remember, your pond is their only home. They have nowhere else to go. Also, ensure you don’t bring any items into the pool with you. 

Can You Pet Koi Fish?

As long as you’re ready for the mild pulling sensation you feel when koi mouth your fingers, yes you can certainly pet them. But don’t overdo it. You don’t want to make your fish feel harassed. These are friendly fish, though, and they may often be receptive to petting. 

A Photo of a Child Trying to Pet and Feeding the Koi Fish
A Child Petting a Group of Koi Fish

New koi owners are often surprised to see just how friendly and intelligent their new fish are. Once your koi get to know you and realize that you’re the person bringing them food, they will be friendly and may even come to greet you. When this happens, there’s no reason why you can’t gently stroke them. It’s strange to think about petting a fish like a cat or a dog, but you can with koi. 

The fact that koi fish have a remarkable memory compared to many other fish means that you can build a relationship of sorts. You’ll get to know your koi and will start to see differences in personalities.

Frank Salvatore

In 2015 our family moved into a house south of Denver, Colorado with a  koi pond.  Since that time I've learned to really enjoy the koi fish and the pond. This blog is dedicated to providing helpful hints and information for koi pond hobbyists - as well as those of you who just inherited a koi pond and are thinking NOW WHAT?

About Me

Hey there - I'm Frank Salvatore. In 2015 our family moved into a house south of Denver, Colorado that had a Koi pond. The problem was I knew absolutely NOTHING about koi ponds.

This blog is dedicated to providing helpful hints and information for koi pond hobbyists - as well as those of you who just inherited a koi pond and are thinking NOW WHAT?
Learn More About Me

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