That ich is present in all marine tanks is a long held, persistent view amongst many reefers. I've even heard it from LFS that I respect. While the statement, in and of itself, is inherently incorrect, I suspect that ich is present in a lot of tanks whose owners would believe otherwise. For example, my 265 has ich and has had for some years now. Most of my fish are asymptomatic, and we're it not for my Achilles tang showing occasional spots, I'd probably have sworn to you that my tank were ich free.