I'm bout to lay muriatic acid to some really tough hard water stains that so far vinegar hasn't gotten out, although a little CLR has. The dab of CLR was just a test to make sure that this was indeed hard water stains I'm dealing with instead of something like etched glass.
Correct me if I'm wrong here, but (new to aquariuming) I'm assuming that the only residual effect from using the HCL acid would be that I would need to do some subsequent pH balancing. Although I'm sure I'll do some serious rinsing after.
So, where do I go to get about a gallon of decently pure HCL acid? I don't want to use the stuff from a hardware store meant for cleaning driveways. I'd rather use something in a rather pure form that won't leave behind anything harmful.