White residue on pool tile

[all4him]

I have a white residue or buildup on the tile along the water line.

I have used a diluted acid mixture in the past to get rid of it but I do not want to keep using acid becuase eventually I am affraid it will eat out the groute.

Is there something a can buy to put in the water to prevent this white film or residue from forming? Or is there something available to spray on it to remove it other than an acid mixture?