I noticed this morning that one of my medium sized male koi, a silver white guy, has some dull yellow growths behind his gills, on the top edge, close to the top of his head.
They seem loose and kind of flappy, but are not really long or big... maybe 1/2" - 3/4," kind of like the thing on top of a chicken's head.
I can't see them clearly, 'cause he's swimming around quite lively and happy. At first I thought maybe he got his head caught in a milk crate, but since they're on both sides of his head, in the same place on each side, it seems like something inherent in the fish.
Any ideas? Is it dangerous, or is it something having to do with the season, or spawn? None of the other fish has the same anomoly, and none of the females are ready to spawn - one is getting fatter, but not ready.