gomezladdams;4356932; said:On a glass tank if the vinegar and razor blades didnt take it off,the glass is etched.
Thats not right.
Vinegar is only a very mild acid for removing calcification/ lime scale, and many stains will persist after it's use even with a razor.
Best way I have found that always works is 1 part HCL (hydrochloric acid) to 10 parts H2O (water).
Apply in a sprayer and mist on the stain and wait about 30 secs. Then wipe off with a clean damp cloth.(wear gloves). Repeat again, and combine with a razor if neccessay. This should do the trick and have never needed to go more than 5:1 on anytype of calcium / lime stain on any glass surface.