Originally Posted by austinsdad
... Lowered immune system causes illness.
Maybe I'm just being anal, and it's a semantics thing... but a lowered immune system does not "cause" illness. If an illness is present, a lowered immune system may allow it to take hold and make its presence known.
And in my opinion (and that's all it is), ich may be present all the time in the ocean, but it doesn't have to be present all the time in our tanks. With proper tank setup and quarantine procedures, the risk of introducing ich to a clean system can be very small.