Hello, my wife chose marine aquariums for her new hobby .. well, we have a 75 gallon tank that we bought used, it came with 4 fish , live rock, pumps, filters, protein skimmer, coral sand bottom, the works.. We saved all the water from the tank when we moved it... The tank is setup since July 15 and all was well until our the flame angel became lethargic and looked sick.. We put it in an isolation tank and treated the water with MarOxy... The fish died anyway.(the flame angel was bought 2 weeks after we got the tank). Now we have a purple tang that has ich.The tang is an original occupant to the tank. We don't know if we can put the tang in the QT with the MarOxy already in that water and then treat for ich.. Do we need to dump that water and start over in the QT?... Also, we were sold "copper safe" to treat the tang.. My wife has read that this is a dangerous treatment and that you never get rid of all the copper.. Any alternative treatments you folks could reccommend.. Please help!.. She was crying when the flame angel died. If we lose the purple tang, I know there will be more tears!.