Originally Posted by DanielaMarie
I have separated the infected fish. Is there something I can/should do to make sure this hasn't spread to any of the others? Do you think it would be more humane to euthanize the fish or wait and see?
One should never treat a tank unless there is certainty that it requires it. Medications stress all fish to some extent, and this weakens them and lessens the effectiveness of the immune system, which means that if something is present, they will be even more likely to contract it--and it might be something quite different from what one treats for, without knowing. One thing that usually does help, no matter what, is a water change. Nothing drastic; just insert the hose and drain out say half the tank, and refill with dechlorinated water. This can work wonders by just refreshing the environment and thus the fish.
When I have seen something like this, it has been confined to one fish and when removed no others came down with it. But again, without knowing what this is, I can't say what may or may not occur. But let's hope nothing in the main tank.
As for the poor fish, if someone can suggest suitable medications/treatment, fine. If this is a virus, there is no treatment for any virus. If it is an internal protozoan, medicated food might help. If the fish is acting normal, one would assume this may not be bothering it too much. If I see fish in obvious trouble, with rapid respiration, abnormal behaviours, etc, I tend to put them down. They never recover, and clear signs of distress bother me.