Ich doesn't appear unless introduced. And no stress doesn't cause ich to magically appear.Being new to the reefing world, my opinion holds little water. However, in the many years that I have been keeping all sorts of freshwater tanks, fish illness (especially Ich) has always been associated with a stress event of some sort. Power going out and the water getting colder than it should, things like that. Ich would pop up on the fish for a couple of days, their immune systems would take over as they de-stress, and poof gone. When it comes to Ich, I am of the school of thought that there really is no way to have a tank with water in it that doesn't have Ich... I am sure someone will want to debate me on this front, from my personal experience even trying the crazy quarantine procedures of multiple tanks separated by more than 10 feet with their own media... etc... etc... etc Ich still showed up in the DT.