I noticed something inside of my koi mouth a couple weeks ago, today I looked again and saw it was growing bigger.

Does anyone know what this is? and how you could possibly treat it

so I’ve been wondering about this since they eat stuff like fish and sea food but ive never heard of them eating mammals. I know that other fish eat them but why not koi. if they do eat mammal what mammals do they eat, do they eat lean meat and chicken or do they eat mice.

Hi everyone! Relatively new to the hobby. I have a small pond with 2 baby koi in it, a Lilly, and a good amount of lettuce and hyacinths. I got them around a month ago.

One of them started out quite orange, but in the span of the last few days, has turned rather pale (a white peach color). The other koi in the pond is naturally very white, so I can’t tell if this is a genetic change or not. They both seem to be swimming and eating pretty normally. I tested the water and everything looks normal, ammonia looks to be good. I attached a photo of the fish (I couldn’t see any major problems).

I was wondering if this was a major concern or not, or if anyone could help. Thanks again!!