Easiest and best way to remove hard water spots on black ceramic tile shower floor and what to do to prevent?

Question:I believe I got the soap scum off with mr. clean ereaser sponge and vinegar on the glass doors.

Answers:
Vinegar should break down the mineral deposits on the tile, too. To prevent it, treat the tile with Glass Magic. It comes in a handy spray applicator, let it haze and then buff it off. It leaves a wonderful shine and will make the water bubble up on the surface of the tile without the mineral deposits forming around the outside. I also use it on my glass shower surround to keep the soap scum from developing on it.