Did you ever wonder how koi chew their food?
They use their teeth.
Koi, goldfish and many other kinds of fish have teeth in the backs of their throats that help them grind up tasty Koi Krunchies and other snacks. These chompers - called pharyngeal teeth - sit on a bone behind the fish's gills.
So could a koi bite you? Not unless you plan on sticking your hand way down its throat. You might be able to catch a glimpse of them if you look hard enough, especially in younger fish, but their teeth are way too far back to put your fingers in jeopardy.
Koi also pose little danger to their pond mates. Koi will suck in just about anything that fits in their mouths - including the tiniest baby fish - but they don't actively hunt other critters. They will harass other fish if they're feeling territorial, but most koi are usually happy to keep to themselves.
The only time you're likely to see a koi's teeth is when cleaning out your pond. They lose teeth just like people do - except they might go through 30 or more sets in a lifetime!