Well, I've been doing this reef thing for a long time now and have had moderate success. Unfortunately, when things are going well for so long you some times tend to get lazy. I recently had an "oh yeah" moment. Over the past month I lost more than half my live stock. I was diligent about QT for some new fish I had purchased, keeping them for about 2 months separate from my display in another 120 gallon tank. They were mostly butterflies and they were doing great. All were eating and none showed any outward signs of disease or illness. I lost two fish during this period, one Long-nosed Atlantic Butterfly and one bannerfish. I attributed this to acclimation loss since I did not see any other fish acting listless or not eating. After a few more weeks, I acclimated them to the 180 gallon by turning on the returns to the sump and combining the systems once again. I moved the new fish in to the 180 after another two week period. Thinking all was well, which it was for about a month or more. One by one, I started seeing some of the new fish die off. I still did not notice and symptoms, one day they would be eating and the next day they would be missing. I probably waited too long to try and treat the tank with a broad spectrum but I had no idea what I was dealing with and what to treat. Over the next three weeks I lost more fish, and I was about to give up. I lost some fish that I have had for almost 20 years, including my Flame Angels. Almost half of livestock died off and I could not stop it. I removed one of the clowns that looked like it was not doing well and started treating in isolation with some Neoplex. It seemed to help and the fish lived for a few more days and seem to improve. I went ahead and treated the tanks, assuming it could not hurt at this point, having sustained losses already. After this point, I lost two more fish but have not had anymore losses over the past three weeks. The Regular water changes and another dose may have helped. The plan now is to wait things out. I'll see how the remaining fish do, again, none show any signs of sickness. As a foot note, I also went back to the basics and thanks to Shac, replenished the cleanup crew in the 180 adding 100 hermit crabs and 100 astrea snails. I had been fighting an algae build up in the tank, when I realized that I had not added any cleanup crew in a long time. Within a week, the rocks and corals were clean as ever! My take away from this is that I probably should have treated the new fish prophylacticly when I added them to the QT system. I was the closet I have ever been to giving up in this hobby, but it looks like I may hang in there for a little longer. Not sure what value there was in this post but it may keep some one else from making similar mistakes. Thanks! Bob