Well, I am kind of the same boat I first had a flukes problem and later discover I also have an ich problem. Too many fish to quarantine so I decided to treat in the display If you are dealing with ich and only base rock (or not very live rock), you may want to consider hyposalinity as opposed to copper. As I am sure you are aware, once you treat the tank with copper it is very hard to get out of the system, and you likely will never be able to house corals or inverts in the tank. Plus, the copper will continually leach for months into the system which will also possibly poison your fish. Also, and perhaps most importantly, it will be very hard to maintain the required copper levels in the tank when you have rock and substrate because they will absorb the copper, thereby makiing the treatment either deadly to your fish or ineffecteive. Although hyposalinity is not very good to do in the display, if you have base rock and not a lot of fauna in the system you can do it in the display with little die off. Plus, your system will not be permanently damaged, and it is no harder to maintain constant hyposalinity levels in the display than it would be in quarantine. I am now starting to treat my display with hypo. It is just taking forever to get my salinity down to the appropriate level because of my large water volume (cannot make r/o water fast enough).