I agree with Tom, but that is for another discussion. I believe Sadie was telling what happened to her tank. From what she stated, she did all the right things. I think ich can be present in a fish (not a system), as a cyst that can stay "encrusted" (look at all the critters that grow on our base rock/dead rock) for as long as needed and just the right parameters can bring it out of it's cyst stage, like temp, stress or moving. From what I have read, once infected a cyst (sorry, I don't have the correct name for this stage of ich, in front of me) will burrow in the the fish's gills or fins and lay dormant until said parameters are reached. (KEEP IN MIND, this is only what I have read on ONE book and am still searching for how long the "cyst" can remain dormant....)
PS, I wasn't yelling, just wanted folks to read the last part.