I have never removed my carbon filter from my Fulval 204, plus I have a carbon filter in my rio 180 internal filter too, its true they may remove some of the treatment but they wont remove it all and I have never had to over compensate for leaving the carbons in. I've had ICH a few times over the years and trust me when I say that you will still get rid of the ICH just as fast if your treating with meds, with carbons in or not. I wouldn't bother taking out any spunge filter media either. Just l;eave your filters as they are, I know I'm probablly gonna get blasted from every1 who reads this message, but I speak from experience so I know the info is not bogus.