Exactly how I run my system. I don't qaurantine my fish, I'm 100% positive ich lives in my system. None of my fish ever show any symtoms unless I add a fish. I added my last fish for the forseable future, a blonde Naso a few weeks back, I observed all of them and the hippo, purple and green coris( pod and coral predator eater) developed a spot or 2 of ich along with the blonde naso. I continued with my heavy feeding regimen and impeccable water quality( tank is full of corals especially acros) and within a few days all signs of ich where gone just like always as I don't quarantine my fish. I think if your fish are very well fed the ich is just a small nuisance for them.full bellies and 'thick' fish means a strong immune system-- nuff said
