Hello, I am new to reefing, but have been interested for many years. I have a 90 gallon tank, that has been up about 7 months. After, about 2 months I started adding fish. One lasted about 24 hours and died. The other 2 died a week or so later. I found out that the refractometer I was using wasn't accurate, and my salinity was to high. I fixed the issue and got 3 more fish. They didn't last long and started dieing one by one. I checked my parameters, took samples to my LFS and they checked them. All was good. I had 2 clown fish. One lives a couple of weeks and died. The other lived. A couple of weeks later I bought another one. After a couple of week's I saw my first clown fish looked to have a white film on them. It died thenbthe other died the next day. The LFS suggested I send a sample to triton in Germany. I took my remaining 2 fish back to the LFS to keep while I get my tank straightened out. They found I had a high level of Lithium, and Sulfur. I was using used food grade 55 gallon barrels for both RODI and salt water. I got on a Facebook page and asked what the issue could be and I got from diseases to parameters. And was told to make a QT tank. Some said I need to cycle the QT tank and others said no. I need to know from someone that has been doing it for years to help me out.