Over the past 2 weeks, I have lost most of my fish. Gem Tang, Purple Tang, 2 Yellow Tangs, Sohal Tang, Tomato Clown, Wrasse, Powder Blue Tang and a Hippo Tang. When this first started happening, I thought it was Ice, but the fish didn't look like they had been infected with that. Their skin was kind of peeling off, and they looked "cloudy" if that makes sense. I tested my parameters, and was shocked to find that my Nitrates were off the charts high. I started doing major water changes....30 gallons/day for days...that seemed to have stopped (well, slowed) the deaths, but I am still losing fish...I am down to 2 fish left. I tested my Nitrate again today, and it is reading 75...maybe my tester (Hanna's new testing device), doesn't read above 75, so it may be even higher than that! I can't imagine why my Nitrates are so high and won't come down.l I use RO/DI water exclusively, dose NoPox (well, just started that a few days ago)....I had a MarinePure block in my sump which I removed...I just don't get it.\n\nOne wild card....I took my Ca Rx offline for 2 weeks, as my Ca/Alk was out of balance. Once I got it in balance, I fired it up again...but the water in the reactor was sitting there not being circulated for that 2 weeks....I didn't refill with new water before firing it back up. Just thought I'd mention this.\n\nAny thoughts? I am of course devastated at the loss of life, but will keep on keeping on...I of course won't add any new fish until I solve this very perplexing issue.\n\nAny help is GREATLY appreciated.