Hello again. Yesterday, I finally added my first fish (Copperband Butterfly) back to my DT after finishing an 85 day fallow period post an undiagnosed fish loss back in May (Tank was fishless since May 30 ((123 days - Food added to tank every couple days to feed beneficial bacteria)), but there was still a tank with fish within 10 feet until July 7 ((July 7 - September 30 = 85 days)), and today she died. History of the CBB: Acquired CBB 8/10 TTM/PraziPro 8/10 - 8/22 Observation 8/22 - 9/18 Second TTM 9/18 - 9/30 (Just to be extra sure that there were no problems with the previous TTM). CBB never had problems eating throughout QT period, acted healthy and active, never displayed any symptoms of a disease. But on 9/30 she was transferred to my 180 DT, and on 10/1 (today) she was dead (shortly after I noticed her breathing heavily/laying on the bottom of the tank -- same symptom of previous fish that was lost in the DT over 4 months ago). First thought was that the flow was too much for her overnight, so upon seeing her breathing heavy I turned off the powerheads to give her a rest, but she still died shortly after. I'm at a complete loss. Water parameters: pH 8.1, Ammonia - 0, Nitrite - 0, Nitrate - 0. First fish in the tank in over 123 days, no fish tank within 10 feet of DT, all QT tanks have dedicated equipment to prevent cross contamination, no signs of disease while in QT, but still died after not even a day in the DT. Marks/gray scales on the top of the fish appeared after she died. Yesterday when she was added to the tank she was clear of any visual abnormalities. My understanding was that after leaving the DT fallow for at least 76 days, I would have starved out the parasites responsible for Ich/Velvet and a host of other diseases that could have possibly lead to my previous fish loss. I maintain a very strict QT process to prevent any possibility of cross contamination, because I did not want to experience such a loss again, but yet I am reliving the same experience after doing what I understood to be the right course of action. I'm not sure where to go next. Any insight would be appreciated.