Sorry introduced myself in How often do u clean your pond?
New to here, so saying helloo to all ponders!
tizzylizzyloo

Welcome, tizzylizzyloo.

Sorry I don't know what killed your fish.

You might want to know that new posts stay at the top until a follow-up is posted, then they begin to move lower. If you write a follow-up to your own post, it won't have the advantage of being at the top so people are sure to see that it has no replies yet.

Sharon

Hope to find an answer...

There is no way to know what killed the fish now that it's gone. There are a couple of things that cause sunken eyes though. Koi Herpes virus does, but so does the parasite Costia. did only the one koi die? Did you get any new fish prior to this one dying?

Yes, only the one died koi died and no, I didnt get any new fish.

tizzylizzyloo