Water splashes which stained outer side of glass

[ilaizm]

Some water splashed onto the outer side of the glass tank. I only noticed days later when the water had already dried up. I am trying to clean the stains but they're not going away!

Any suggestions as to what I can use to clean them?

[Cuchulainn]

You could try a utility razor blade. Just be sure and keep the surface wet with water while scraping it off and you won't have scratches on the tank when your done! ;)

[Darrell Ward]

I agree. Mineral stains usually have to be scraped off.

[Sean Buehrle]

use vinegar the acid will disolve the alkaline deposit.