Hi, I'm new to this forum and have a question about the health of my 3 Koi. They are in a 700 Gallon outdoor pond with a bio filter system, one large waterfall, a stream and another smaller waterfall. The 3 koi in question have been in the pond for at least 3 years. They are between 12" and 15" long. I never had problems with their health, but I think they might have a parasite. We had ducks in our pond this Spring and I don't know if they maybe carried the parasites into the pond. We also just got 3 new 4" koi from a reputable source. I contacted him already and he had no complaints about any of the koi he sold that were in the same batch. It seems as well that the 3 new ones are not affected. The water test came out normal, but we did 3 or 4 water changes already and added some Kock-Out. One of the Koi started about 2-1/2 weeks ago being lethargic, not feeding and flashing. Then all 3 did the same a few days later. With all the water changes and the Knock-out they are improving. They are more active, feeding a little bit and not as scared anymore as they were 2 weeks ago. They were actually so tame before all this happened, that I could feed them by hand. We were away for 4 days and just got back today. I was shocked to see that the one that was actually affected the least before, looks terrible. See photos. I really don't know what it could be. I thought it was Ich, but now I'm not sure. I didn't do a scrape because I didn't want to stress them any more. I also don't know how to do it and haven't found a place that would test the scrape here in Edmonton. Any help or suggestions would be greatly appreciated. I really don't want to loose my pets.