The best way to get rid of the calcium build up is to use a grout trice to remove it from the surface the only other way is to use CLR but that is a harsh chemical ounce you remove it with the trice i use my product to color the grout and make it water resistant and that stops it from coming back.If you have any questions call us at 1-800-631-0716 michael
Try vinegar. Clean it off with the vinegar and then put a small amount of vinegr n every time you refill it.
I know of no sure fire way except soaking paper towels in CLR and wrapping it around the area and letting it sit for a while. It is a harsh chemical tho.
Since animals and birds can get to the outdoor fountain, I would not use CLR, it is a poison. Use vinegar, it may take one or 2 tries, but will not harm and living creature