I hardly dare admit that I have had it about four times, after those virtuous posts above
I have a particularly virulent strain at the moment that has been thriving for weeks and weeks at 30 degC and in the face of three different meds

. I think I have it licked now

- but need a few more days to be sure. Someone at Wharf Aquatics (giant among lfs's) told me that there are a number of different ich strains about these days - all with different resistances to heat/meds.
I should say that I have six tanks and have had them for two years - so some of my tanks
have never had ich
I think that many, if not most, new fish from an lfs are carrying ich. All my outbreaks have been in new fish shortly after they arrive in my tank. It might just be the stress of the move that brings it on - or it might be aggression from their new tank mates.
I'm not sure how it can be avoided. I guess a quarantine tank would help - but the majority of us don't use one (recent poll) and that won't stop initial tank mate aggression.
My pentazona barbs came out with ich, after being added to the tiger barb tank (not surprisingly perhaps!) but after a couple of weeks (and some meds) they had completely settled in and have been fine now for more than a year.
The current outbreak is in cardinal tetras who were added to a tank containing four sparkling gouramis (not particularly noted for aggression) - but the gouramis bullied the cardinals relentlessly. In this case I moved the aggressors out.
IMHO ich can't be totally avoided in community tanks - if you're going to add new residents from the lfs
