Noticed that when I introduce salt into the pool that I get the green tint which, short of draining and refilling, is easily solved with sequestrant (Jack's purple stuff). Reaction happens about 30 minutes after introducing bag(s) of salt. I'm curious as to why this happens? I'm using regular salt from home depot at $5/bag vs pool store $30/bag. Are there metals in the salt? Does the salt react with the metals in the water? Figured some of the chemistry majors might be able to satisfy my curiosity.