Water seemed perfect when leaving on short 4 day vacation.
Returned, opened pool and had black stains??? Will try to attach photo...
Water chemistry when we returned on 6/13/16 @ 2:07 PM:
FCL = 9.23
TCL = 9.59
Br = 18.0
PH = 7.3
ALY = 147
CH = 165
CYA = 79
Water temp was 90F due to recent heat wave
Tried PH reducer directly on stain; no noticeable effect?
Added "Algestroy" provided by Central Pool
Tried brushing today, 24 hours after adding algaecide... no joy!
Read this article and thought I try some of those recommendations: Know Your Stains| Pool Spa News | Water, Metal, Cleaning, Spas