A week ago I found my ghost koi lying in 1/2” water in the stream which runs into my pond. I don’t know how long he was there but he was still alive. I am assuming he had jumped (although I have never witnessed him doing it before). He had no signs of injury but the exposed side of his body had become dry. I placed him back into the pond. He was very still for several hours but then began to swim around. I noticed over the next couple of days that what was the dry side of his body was beginning to peel off, but he appeared to swim around and eat ok. I then didn’t see him for approx 4 days. I had assumed he had died and was somewhere in the pond. Yesterday I saw him but he appeared to be covered in what looked like thick black hair, but on a closer look, looked more like algae. Does anyone know if this is a healing process where his body had become dry? Or is this some sort of disease which will eventually kill him. I don’t know how old he is but I have had him approx 11 years. He is approx 12” long and was a beautiful bronze colour. My pond is 18’ in diameter. I have plenty of other fish and have never had any illnesses and very few deaths over the years. Any advice would be gratefully received. If he is dying, I don’t want it to be drawn out. You can see him in the top left corner of my photo.