It has been proven that corals can transport Cryptocaryon irritans as protomonts or tomonots, but not host.
"Cryptocaryon irritans is a ciliated protozoan parasite of marine teleost fish in tropical and temperate waters. This pathogen is an obligate parasite of marine fish (Iwama, Pickering, Sumpter & Shreck, 1997.Dickerson & Dawe, 1994)." Meaning, it can’t survive without a host,which must be a boney fish.
I agree with you that people that QT for 8 weeks still get it. Heres why -it wasn’t treated. The fish they QT’ed had subclinical symptoms, or rather had it, but you wouldn’t be able to tell without a biopsy. Perhaps one Trophont in the fishes gills, that’s all it takes. QT isn’t a treatment, it is for observation, and if the person doesn’t observe Ich for 8 weeks, they think thef ish is good. They then add it to the DT. Next week you get a ph spike, tempswing or whatever, and the fish now is covered in it? Why? The stressor weakened the immune system of the fish, allowing the parasite to gain a better foothold.Once again, as you said misinformation is to blame. Fish stores and many peoplein the hobby say, QT it, then you’ll be fine. This is a farce.
What happens next? The fish keeper goes on line, and says "I qt all myfish and corals for 8 weeks, there is no way I have Ich, but I do." Every one takes this to mean Ich magically appeared in the fish keepers tank, which wasn’t the case, it was introduced by a fish, that had subclinical symptoms. Had the fish keeper used one of two, scientifically proven methods, (Copper or hypo) to treat the fish, regardless of symptoms or lack thereof, he wouldn’t have Ich in the DT, wouldn’t be perpetuating incorrect information, and the hobby would be that much better for it.
That’s, all. Good convo.