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Do Koi Fish Bite?

Do Koi Fish Bite?

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Koi fish have an uncanny ability to enhance a home’s aesthetic value with their tranquil presence and vibrant personalities. Part of the appeal of raising koi fish is getting to feed them by hand since they are usually gentle ornamental fish. You might know koi as fish with large and wide mouths, especially since they can grow up to 15 inches long, and that’s not even the jumbo kind. With their large mouths, you might often ask yourself the question, “Do Koi Fish Bite?”

Koi are just like other fish that need to feed, so yes, koi fish can bite you. Their bite is not strong enough to cause any significant harm to humans, but they may threaten other fish you are raising alongside them. This article discusses koi teeth’ main function and potential threats to other fish and your entire pond.

Do Koi Fish Have Teeth?

Do Koi Fish Have Teeth?

Koi fish have pharyngeal teeth that go far back down the throat, past their gills. A lot of freshwater aquarium fish like goldfish and loaches have these kinds of teeth. While koi do not use their mouths to chew food the way mammals do, koi have developed their pharyngeal teeth to grind and crush food into smaller particles for digestion.

Since koi fish’s teeth are in the back of their throat, you don’t have to worry about them biting you when you feed them by hand. You might feel a pull or suction sensation when you slip a finger into their mouth, but this should not be strong enough to feel any nibbling.

Additionally, koi tend to “taste” the things they put in their mouth before allowing the food to meet their teeth. Your fingers should be safe from your koi’s pharyngeal teeth when the koi realize that your fingers are not the most ready-to-eat object in their mouth.

It’s unlikely that you will get any accidental injuries from koi bites. You may incur koi bite injuries if you deliberately manhandle your koi fish and it struggles to get free. Otherwise, you can rest assured that you are safe to feed your koi by hand should you want to get acquainted with your koi fish. Koi fish are known to recognize owners who regularly feed them, making these animals unlikely to bite the hand that feeds.

Are Koi Teeth Dangerous?

Koi fish can shed their teeth just as humans do to make room for new teeth. However, unlike humans who only shed and renew teeth once, koi can shed over 30 sets of new teeth in their lifetime.

You might notice these shed koi teeth at the bottom of your pond when you conduct scheduled maintenance. Sometimes, koi teeth get clogged in your filters when your water pump sucks in the water for filtration. Since koi teeth are hard enough to chew food, stray koi teeth may damage your filter media if you do not regularly clean your filtration devices.

Koi teeth are small white objects that your older koi fish may shed when they need to. There is no set interval in a koi’s lifetime when they make room for new teeth. So, you can never tell when these old teeth may turn up in your filter boxes or at the bottom of your pond. Be sure to maintain a regular pond cleaning schedule to make sure your equipment remains in optimal condition.

Do Koi Fish Bite Other Fish?

Koi fish are not hunters and do not actively hunt for smaller fish. They are only aggressive when they are mating, and that includes mostly the male koi fish. They may bite the female koi fish they mate with to the point of damaging their fins and scales. Your female koi fish may get ill due to damaged fins and scale loss, especially if your pond has poor water conditions.

A 2011 experiment investigated koi’s aggressive behavior toward fancy goldfish. The experiment discussed how the author observed three types of aggressive behavior that koi exhibited when living with fancy goldfish: biting, mock biting, and chasing. Biting resulted in tears to goldfish fins, leaving them prone to diseases.

The study described mock biting as koi fish seemingly biting the area around other fish without actually biting them. The study observed that koi fish chased the fancy goldfish more than they bit and mock bit them. The author concluded that koi and fancy goldfish are not suited for coexisting in the same pond.

Relatedly, you must be careful when raising koi with other fish like tilapia, especially if they are smaller. You risk having your larger koi feeding on the smaller species. While koi fish do not actively hunt smaller fish, poor water conditions and individual attitudes may contribute to your koi’s eating behaviors. Anything they can get into their mouth may end up becoming food.

In rare cases, koi fish establish a pecking order, meaning the larger koi fish tend to be in charge of the entire gasp of koi. The larger koi fish may assert their dominance in your pond by nipping at the smaller fish’s fins, which may leave them injured and develop illnesses.


Koi rarely bite your fingers when you feed them by hand, but it is still possible to slip a finger in their large and wide mouths. However, koi fish have pharyngeal teeth behind their throat and gills for chewing food, so it is unlikely that your fingers will reach far back in your koi’s mouth to get bitten.

In terms of other fish in your pond, larger koi fish may bite smaller fish to assert dominance. This behavior is common in poor pond conditions, so you must be sure to maintain an appropriate environment for your koi.

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