Black/grey shadow on porous rocks above water line

EmmaApp

Well-known member
May 29, 2017
82
Houston
HI

Not sure if it's "black algae"...

We have a blackish shadow on porous rocks above the waterline, but I think it's affecting the FC/CC levels.

I did a SLAM ending in an OCLT of 0.6ppm and CC of 0.
The brand new jandy SWCG is set at 50% and is "maintaining" FC at 7 (I'm deliberately keeping it on the high-side because of the rocks). But the CC is creeping up and has got to 1.2 in only 12 days.

The pool looks great! Nothing below the waterline. The skimmer baskets are clean, the filters are new and the SWCG is less than 1-month old. I use TF-100 test kit. We even switched out the Polaris bag.
Recent levels are:
FC 7
CC 1.2
pH 8.0 (before 3/4 gallon of Acid)
TA 90
CH 350
CYA 70
Salt 3400
Temp 83F

Is there a homemade bleach spray we can use on the rocks - that's the only thing I can think of that's causing the rise in CC.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
19,500
Northern NJ

EmmaApp

Well-known member
May 29, 2017
82
Houston
It would probably fail the OCLT (just a guess). We've had problems before and just poured the bleach over the rocks, but this time it's not budging.

I have a love/hate relationship with our pool. It's 17-yrs-old and we inherited it 2 years ago. It wasn't well maintained and there's HUGE calcium deposits (where historically there were unrepaired leaks), the Texas Sandstone rocks are disintegrating into the pool (because they were improperly sealed and we can't afford to fix and reseal yet) - not to mention the porous nature that holds on to algae!, and the plaster slide can't be used because it tears-up swim suits because it wasn't maintained. All the previous poor maintenance issues would cost over $1500 to fix and probably more. Living in Texas, we appreciate having it and we're in nightly with our son... but OMG it's bugging the **** out of me!
 

EmmaApp

Well-known member
May 29, 2017
82
Houston
Does your water pass an Overnight Chlorine Loss Test now?

You probably have black mold on your rocks. I use


on stones around my house for green and black mold and mildew.

in regards to this product, what are the ingredients? It says "No Bleach" but I thought Bleach was the be-all-and-end-all of pool cleaning.
 

ajw22

Gold Supporter
TFP Guide
Jul 21, 2013
19,500
Northern NJ
in regards to this product, what are the ingredients? It says "No Bleach" but I thought Bleach was the be-all-and-end-all of pool cleaning.
This is not pool cleaning. This is creating an environment on the stone that mold and mildew can’t live in. The spray changes the pH of the surface to something that kills mold and mildew. It is safe around plants. Simple and effective.
 

EmmaApp

Well-known member
May 29, 2017
82
Houston
This is not pool cleaning. This is creating an environment on the stone that mold and mildew can’t live in. The spray changes the pH of the surface to something that kills mold and mildew. It is safe around plants. Simple and effective.

Do you use it at/near the waterline? I'm leery of using anything that would add unfavorable ingredients to the pool