This morning I brushed pool and I had slight yellow mustard (I guess that s redundant) on one wall. I checked water yesterday and CC was 4.0. PH was 8.0 so I added 1 cup acid. . This morning CC was 3.0 and pH was 7.7 so I added 1/2 cup more acid. We have people coming by today for BBQ/pool party so I didn't want to shock it yet...is that dumb? I just added a slight (pint) of chlorine and I will shock it tonight. Is I will keep an eye on chlorine today in case the algae is gobbing it up.