Hard water stains

[Drkphant0m2]

So I have a serious case of hard water stains at the rim of my tank. I just bought the tank used and have tried everything to remove them. I scraped it with a razor blade, applied vinegar and lemon juice and even applied clr (The tank is empty of course). But nothing works. I know that when I wet it, it does disappear but after drying, it comes back. What can I do? (I also have a minor case of scratches on the tank so in addition to the stains what can I do about that)

 

[AngieD]

I don't think anything can be donee about the scratches, but I've just looked up the hard water problem online, and it appears that making a paste from white vinegar and baking soda, smearing it all over the marks, and then cleaning it off after 15 minutes is an effective solution (and won't choke you with chemical fumes). It might need to be done more than once for really bad stains.
What are you planning to put in the tank?

 

[Ed]

People need to keep in mind that severe water stains can actually impact the glass by bonding to the glass itself and/or etching the glass. Is isn't uncommon to end up with tanks where the only way to remove the stains is to buff them out of the glass.

Ed

 

[Jennewt]

Right, at some point you are left with a "haze" that nothing will remove. Some of the deposit may consist of silica, and since silica=glass it is unremoveable. Since it's a used tank, my advice is to just live with it. If appearance really matters, replace the tank.