I've been having my Koi for almost 8+ years and this is the first time that any of them have gotten sick . Can anyone tell me what is on my Koi's skin/scales? and perhaps how to treat it? I have a total of 14 Koi in my pond and this one is the only one suffering or being affected by this condition. A couple of years ago one of my fan tail Kois was suffering from tail rot but that was relieved by a complete water change. I did another complete water change to see if it would help the condition if this Koi but it did not work. Help please!!!!!!