I don't use a synthetic salt, I use a natural seawater. It is a premix all I do is pour it in. I have used it since the start of my tank. Perhaps I got a bad mix? If that is the case then why didn't my inverts, turbo snail and peppermint shirmp die? Hmmm...I am at a loss and not quite sure how of if I am supposed to treat my tank if I don't know what happened. I thought about just throwing in the towel but I have worked so hard on this tank to give up on it. Once again, "Thanks" for all the input that everyone is putting in. Hopefully someone can help me figure this out.