Blackspot Algae-Need Advice

[ac130loadmaster]

Hello all,

I switched to the BBB method at the beginning of the summer and you guys have helped me create an awesome sparkling, chemically balanced, and best of all cheap to maintain swimming pool. But last week I started noticing black spots all along the walls of the pool. I have counted about 11 or 12 spots. They are basically all even with each other around the pool. I have taken a brush and gone over them and they will not wipe off. So I have assumed it's blackspot algae anyway. I have began shocking the water at yellow mustard shock level and have brushed twice today. Does anyone have any other advice? I heard this is hard to get rid of and I have closed the pool till I get this resolved. Kids and wife not happy! Here are my numbers:

TC 25
FC 25
CC 0 (Is this possible?)
pH 7.5
TA 100
CA 243
CYA 35
Borates 45 to 50
Salt 300

Thanks everyone,

Al.

 

[frustratedpoolmom]

Can you post a pic? brushing has no effect whatsoever? doesn't sound like BA.

 

[ac130loadmaster]

Here is a picture. I have about 12 of these in the pool. Scrubbing doesn't do anything to them

 

[Butterfly]

Try testing a spot w/a vitamin C tablet.