:help: 2 days ago, I had to make some maintenance work on my aquarium (20 liters) which required removal of my goldfish (total of 4). After placing them back, within 24 hours 2 of them developed a mild case of ich which was promptly treated. I have noticed that one of them (a comet-tail) seems to have sustained tail injury with a tear that goes almost to the base, and now it tends to stay on the bottom moving only for feedings. Has anyone had a similar experience, and how long should I wait before getting concerned?