I'm using this stuff: http://www.lesliespool.com/Home/Pool...ock/14181.html

I apply it into the skimmer. Yeah, I know (now) that I could use bleach from the grocery store, but I bought this in bulk, so I thought I might as well keep using it as long as I have it. Do you see anything about it that could be harmful? My assumption is it is just granular chlorine that dissolves quickly.

I'd also kind-of like to know for future reference. I want to support my local pool store, and I don't mind buying chlorine there, even if its more than I'd pay for grocery items at Wal-Mart.