sick koi

Question
One month ago, I found my favorite koi floating on top of the water.  He was still alive so I scooped him up and brought him inside.  He seemed to be getting better since I was hand feeding him medicated food, but the ammonia levels kept rising in the 100 gallon container that I had him in.  I kept changing the water but someone told me that it wasn't good to keep changing it and just try to get it under control. Today when I came home from work, I noticed him just floating on his side again and his one eye is all cloudy. I immediately changed his water and the chemicals are where they should be but it breaks my heart to see him ill.  What else can I do for him?

Answer
I'm sorry about your koi.  You may want to contact your local koi club for ideas.  They sometimes can come and diagnose sick fish.  It's ok to do say 30% water changes once a week or so on the container.  I suggest adding dechlorinator, good bacteria, and pond salt (a tablespoon per 5 gallons of new water or maybe a little more). Cloudy eyes can be caused by physical damage, bacterial infections, parasites, and other things.  It's usually bacterial.  You may want to treat him with something like Maracyn I by Mardel which is erythromycin.  Be sure to aerate the water well.  What were your test results?  I suggest testing for pH, hardness, ammonia, and nitrite at least.  If there's still ammonia, you might add some Ammo-Lock.  If you do, the test kit will still be positive for any locked up ammonia even though it's not as toxic at that point.  What kind of a biological filter do you have in there?  How big is the koi?

Good luck!