Glass residue? Nothing has worked

After completing my 400 build I noticed a residue on the glass. I’m not sure what it’s from but I don’t remember seeing it when I started. Maybe I didn’t look close enough, b/c the glass was used from an old tank. I have been trying to clean it for a while now but I can't seem to get it clean. What can I use to clear the glass up. I've tried scraping it with razor blades, using apple cider vinegar, stronger industrial cleaners, but nothing has worked. Is there a way I can buff it out?

Any advice? Thanks

cali~budfish said:

Try car cleaner wax. Do a little circle spot to test and see if it works. It won't harm your glass either. Does the residue seem like hard water stains?

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It is very possible that they could be hard water stains. I'm not really sure, I dont see how I would have missed it when I was building it but I guess I did...

zukiGS500 said:

Is it on the inside or outside of the glass? If it's on the inside it usually disappears when you fill it with water.

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Its on the outside, and its full of water and you can definetly still see it...