Can Ich attack healthy goldfish? I had 2 new goldfish bought couple weeks ago, they showed sign of ich within few days, but I kept changing water and maintain a good water condition the ich disappeared after a week. I just got a new black moor yesterday and I saw sign of ich today, lucky I put him in my quarantine tank. When I do his water change, I accidentally forgot to change the same container that I used to scoop out quarantine tank water, when I scoop the main tank water to the quarantine tank. I'm afraid of cross contamination here. I was wondering does the ich attack healthy goldfish?