The clerk at my local pool store tested the water and said that my Ca hardness was worryingly high. His test showed 300 and it's a plaster pool so I'm not too worried about it. Then he sent me home with a Cal Hypo shock to clear up the CC. I had already dumped it in the pool when I realized that I was adding yet more calcium to the pool at the suggestion of the guy who had just told me I had too much calcium! I suppose that makes me a fools accomplice.