In the quest to further prevent metal stains my 10K FG IG pool, I added 15lbs of Calcium, as a suggestion. I started with 0 and I think I got it up to about 250. I was having trouble with reading my test kit but I believe it got me to 250.
About 4 days after adding the Calcium, my pressure on the (sand) filter had drastically reduced (10lbs) and return jets had bad flow. This never happened since I've owned the pool - I rarely have to backwash. I backwashed and it restored the pressure back to normal. After that, my Calcium tested 0. I had the Calcium tested at Lelie's today and they too got 0. They tested it twice and they were very confused when I told them I added Calcium just about 2 weeks ago. I can only surmize that the filter grabbed all of my Calcium !! At the same time I put in the Calcium there was a ton of sequesterant in the water and I did add some afterwards, as well. As I said, I'm battling with stains.
Could the sequesterant have done something with the Calcium for it to end up in the filter?