I know the feeling. be patient super patient with the 75G and you will love the results man. In my opinion, (correct me if I am wrong folks) after about 8 months to a year you can do almost anything you want to your tank as it really starts to get its bacteria and life cycle going. If I were to redo anything in my tank now I would probably wait a year before adding any corals or "special" fish like the mandarin. I think by waiting you really give the eco system of a tank a big chance to help yourself in the long run. I hope everything works out for you and sorry to hear about the mandarin. I will be home today if you want to drop the bits off. I have a water change to do and then dose everything again.