Hey david I would qt all infected fish and leave your main tank without fish for 6 to 8 weeks to kill off the ich. i would use cupramine to cure the ich it works great and is not as hard on the fish as regular copper. No tank will have ich in it if you qt all your fish when you buy them. Also if moving fish stressed them and killed them then every fish you take from the fish store to your tank I guess would all die then because then their moved twice. Good luck keep us posted