Julie,

I don't know enough to make suggestions but certainly can sympathize with you. Sorry you lost your Koi.
Anne

Julie, is there any aeration in your pond like a splashing water fall or fountain? You might want to invest in an air pump if you want to keep any more koi in there.

My pond does have aeration. Thank you for thinking of that possibility.

Have you added any new fish lately? What is the temperature of your water? When you say the koi are all dead and the goldfish are fine, it makes me thing of a terrible possibility. Koi Herpes Virus kills only koi and leaves goldfish untouched.

KHV is a herpes virus, so the virus can live in a koi for a while before it breaks and causes the disease. Think about how chicken pox works in humans. As a child, you get chicken pox. Then you recover, but the virus still lives inside on the nerve endings. Years later when stressed, the virus fires back up and causes Shingles, a painful disease of the nerves. And a person with shingles can give chickenpox to a child. KHV acts the same way. When a pond is infected with KHV, some of the fish die and some survive. The survivers are now carriers and will infect other koi at some point. All fish that survive KHV should be destroyed and the pond sterilized to prevent reinfection of this deadly disease. The bad news is that if it was indeed KHV, the goldfish are now carriers as well. Since you have no koi left to test though, there is no way to confirm that it really was KHV.

Here's a link to a web site that explains more about KHV.

Here is a link that might be useful: KHV web site