Skimming over, I'm not exactly sure over the details discussed (quite enthusiastically I might add) , but I have a link I can post about fish immunity, which makes reference to a scientific journal dated 1998, which I have also read. This should clear up your debating in regards to stress and immunity?
http://www.reefkeeping.com/issues/2004-07/sp/feature/
Treatment Option 1: Natural Immunity
"As with
Cryptocaryon irritans, it has been demonstrated that fish can develop immunity to
Amyloodinium ocellatum after several non-lethal exposures, and that this immunity can last for at least six months (Cobb, Levy, & Noga, 1998). "
Here is the link to the journal article, which describes the procedure.
http://www.researchgate.net/publica...inoflagellate_Parasite_Amyloodinium_ocellatum
ABSTRACT The dinoflagellate Amyloodinium ocellatum, which causes amyloodiniosis or ?marine velvet disease,? is one of the most serious ectoparasitic diseases affecting warmwater marine fish culture worldwide. We demonstrated that tomato clownfish Amphiprion frenatus can develop strong immunity to infection following repeated nonlethal parasitic challenges. The protective response is long-lived and directed against the trophont stage of the parasite.
I have used this principle to induce herd immunity in my tank, by having immune carriers (chromis and zebrasomas) develop an effective immunity (or resistance if you would like) to the specific ich strain in my tank. Once asymptomatic, I was able to add non-resistant fish, one at a time, and induce immunity in them, until the ich population died out naturally within 9 to 12 months.