So, I'm cleaning the used tank I bought and there is something about that glass that is bothering me. I'm using a vinegar/water mixture and it's working very well for most of the tank, but there are spots on the sides that look cloudy. When I get them wet, the cloudiness goes away but then returns as soon as it dries. I've been using a razor to scrape off everything that is stuck on, but even that isn't helping in these areas. Is there anything that will get rid of the cloudiness or am I stuck with it?