I have a 75 gallon Oceanic glass fish tank that has a buildup on the inside wall (calcium?). I am not sure what it is, but I tried vinegar with a dish washing pad when I have the tank empty. I should spent more time trying to clean it before I set the tank up. Anyhow, now that it is setup...I tried scrubbing with different types of pads, and I tried a razor blade. Whatever it is, it is on the glass good. What do you think it is and what do you think is the best way to remove this? I know I may have to break the tank down again to clean this off.