I have a pond that is about 1000 gallons with about 8 Koi over a 1 1/2 long and some koi/goldfish mix (by accident). I've had the pond for at least 8 years. It has a liner. Most of the time the water quality is good unless I have a "run" on algae and have to go through all sorts of moves to get rid of it but that doesn't happen often. I've noticed, or thought I noticed, that my oldest butterfly koi/goldfish mix, (about 8 yrs old), seems to have some crystal looking things on her fins. She's only about 10" of so. I also have a butterfly "koi" that's about 8" that I've only had for about 2 months and she seems to have the crystal looking bumps on her fins now. She didn't have them when I got her. It's really hard for me to catch my fish even with a net so I don't have a photo of the crystal bumps on their fins. I can get a photo if it's absolutely necessary for safe treatment but I hate scaring them because it takes awhile to get them to trust me again. My question is why don't my regular koi and other fish have this on them. How can I treat this safely? Should I treat the whole pond or isolate those 2 fish in a different tank and teat them? I have included a photo of my butterfly koi but you can't see the crystals. I've also included a photo of a random beta off the internet that has what looks like my 2 fish have. Thanks for the help.