No, no, no, no, a thousand times no. You read up on it (the skeptical aquarist's site listed above is an excellent start). Peter Burgess, who did his thesis work studying ich said it is "utter rubbish" that ich is present in every tank. I have more links, but because search is not working on this site at the moment, I can't post them right now. Once search is working, I can give you many other references, including a 30 page review article written in 2005 that summarizes all the known research about ich at the time that makes no mention whatsoever of a dormant stage in ich's lifecycle (which would be needed for it to be in all water). Dormant ich is a myth propagated by the hobby, the scientific literature is very clear on this, there has never been a single strain of ich ever studied that had a dormant stage in it's lifecycle.
