Get a QT and treat your fish in there, not in the display tank. Copper is toxic to all corals. Im not sure if the Seachem Metronidazole will work. Im going through some ich issues myself and i purchased Cupramine made by seachem. Its working great and all my fish are healthy. I was also told to raise the temp in the display tank and lower the salinity over a weeks time so the level is around 1.013, sounds crazy because corals dont thrive in that low salinity but actually they have been doing fantastic. Im going to be keeping it at those levels for a few weeks so no ich will be present in the main tank. You can try this method to if your main tank was introduced with ich.