Originally Posted by cmc3502
so my QT tank can start off with new salt water?
If your main system (DT) doesn't have any problems (E.G. ich outbreaks) then I'd populate the QT with water from the DT. When you do water changes, move drain water from the QT, replace it with DT water, and put new seawater into the DT.
This way you are adding "cycled water" into the QT which will help keep your levels in check, and it has the benefit of getting your new fish used to the DTs conditions. Of course, your DT is currently suffering an outbreak, so doing this may very well transfer ich into the QT, causing you more problems.
In your case and moving forward if you have an outbreak in the main system that you are treating, use new seawater. Do a 50% water change every other day and add Seachem Prime on opposite days to keep ammonia from becoming toxic.
Another thing you may consider is to run your QT in hyposalinity for new arrivals, of course this means mixing new seawater for them. A 28 day quarantine period at 1.009 will ensure that no parasite survives and passes into the main system. The one drawback to this is it takes days to get your salinity back up to the main system's salinity level before you can even try to move them into the main tank. Coming from 1.009 to 1.020 or more cannot be done in hours of dripping, it takes days of adjusting.