I'm not sure how to post links to a past post, but you can go to a post entitled, "Calcium" on this forum with a date of 7/1/06 and you'll see the whole discussion of DowFlake as a calcium increaser.

You might want to encourage your ex-neighbor to check out this forum as it appears his/her chlorine levels are not adequate for a CYA level of 90. You did your ex-neighbor a real favor testing the water for them and giving them some direction .