What should I use to clean this tank from a stain? I've cleaned my tank with bleach, vinegar, baking soda, CLR, and comet. It looks like a hard water stain, that's on the outside of the tank. When you run your fingers over it, or a sponge, it feels rough and not smooth like the glass. It's a stain that's 'cloudy' and whitish/faint yellow in color. This tank used to be a home for african cichlids, if that helps any.
Should I try an abrasive cleaner? Some strong chemicals? (I can rinse out the tank later, it has not been set up yet...)
Thanks for your responses!