Is this algea?

[HogT1de]

New pool owner. Backstory: Bought house in 8/24 gunite pool needed to be chipped out and resurfaced. Diamond Brite French Gray installed. After install I did what contractor instructed with chemicals and brushing twice daily for 28 days. After a quick stint with test strips I was lucky enough to find TFP. I ordered TF-Pro- Salt kit and was off and running (stumbling). Lately I've noticed small black spots/streaks along the walls. Not many but enough to make a newbie concerned. In this pics is that algea I'm seeing?

Pool 33000g, Gunite, SWG

FC - 7.5
pH - 7.7
TA - 80
CH - 400
CYA - 70
Salt - 3600
Temp - 83
CSI - -0.04

 

[Texas Splash]

Welcome to TFP! Good job testing your own water with a great kit. Numbers look good. From my screen, it doesn't look like algae. Instead it looks like something fell in the water and left a streak Tannin marks are kind of similar. Do you have a lot of trees nearby? Have you tried testing that stain with anything yet? If you have some cal-hypo, you could thy and place some cal-hypo granules on the stain for a short time to see if that helps. Or rub chlorine tablet on there. Keep it moving though and not sitting in one place. Those are for organic tests.

 

[HogT1de]

I thought it could be scuff marks but there are no trees overhanging and I'm cleaning pool daily (semi-retired). I'm going to do an overnight chlorine test tonight even though my water is clear.

 

[Donldson]

Has the lawn been fertilized lately?

 

[HogT1de]

Good call. Yes. I think they put out some granule fungicide.

 

[Donldson]

Ah ha, I thought those looked like copper stains but generally granular fertilizer has iron and maybe trace amounts of copper. But fungicides often have copper in them.

I'd try to find out what kind was used to confirm (not all have copper and if it's not a copper stain then it will likely fade away over time from the chlorinated water) but if it is copper then you can treat it with Jack's Stain Solution #2.