Yes it is fine. I have done exactly the same thing, I was given a 46g bowfront that was used for salt. This one had been left to dry, and was covered in some hard green and yellow stuff. I soaked it in vinegar water for 3 days, and then scraped it off with a glass scraper. It looks brand new and I haven't had any problems with it. I thought it was kind of stupid when I heard about it, and that it would make things look distorted but its very nice.