I think we need some more specifics. What was the time line related to the fish loss? You said you are not having luck with fish but also stated you have multiple gem tangs and a moorish idol (which are notoriously hard to keep). Is this just a recent span of bad luck? How many fish did you lose? How much time passed between the deaths? Did you re-establish the biofilter between the deaths / draining / bleaching? Are you sure the tank is completely bleach free?