white flakes at bottom of pool by hot tub run off

[lona2u4u@yahoo.com]

I have a salt water pool and noticed I have algae growing even though the cholrine level is normal. I put in a Phos-free solution to get rid of the algae and it never seemed to make it through the system. Now I noticed white flakes on the bottom of the pool next to the where the hot tub spills over into the pool. The flakes are loose and do not stick to the pool bottom. The Calicum hardness is at 170 which I was told is slightly low.

Any ideas what this could be? The pool store employees did not know.