Need assistance identifying this, algae maybe?

[mhr7176]

I am fairly new to keeping up with my own pool. I have done research on chemical levels so have a decent understanding of those. Back ground is we have had this house for about a year. Pool was originally salt water and we converted to tablet chlorine back in May. I used a pool company over the summer as we traveled a lot and they got my CYA well over 100. So they drained it in August and reset the chemicals and even then got the CYA around 60 right off the bat. So I stopped using them and took over the pool work myself. I know the CYA is still high so may not have a choice but to drain it again soon to reset the CYA. I also know the FC is low so trying to get that back up. But my question for now is what are these spots? They were there when we bought the house and haven’t really grown much (maybe a little but not much). I mainly want to know what they are on how to get rid of them. Thanks in advance.

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Test Results 10-27-2023 @ 12:17 PM
Free Chlorine: 3.0
Combined Chlorine: 0.1
pH: 7.6
Total Alkalinity: 60
Calcium Hardness: 230
CYA: 75
Temperature: 81°F
CSI

 

[mknauss]

Welcome to the forum!
That appears to be iron staining from rebar or other metal near the surface of the plaster. Get some Vitamin C tablets, put them in a thin sock, crush them a bit, and set it on the stain. If it disappears, it is iron.
Your FC is very low. See FC/CYA Levels
Why did you get rid of the Saltwater Chlorine Generator? By far the easiest and most reliable way to add chlorine to your pool.
I suggest you read through Pool Care Basics - Trouble Free Pool and even look at a few of our videos TFP-TV - Trouble Free Pool

 

[mhr7176]

Ill check those out. Thanks for the feedback, much appreciated! For us we
Got rid of the saltwater because it was just wearing down the metal parts of the near by bar, tv arms, and few other objects. I guess we could have replace the metal with stainless steel or something else but that is the path we choose.

 

[mknauss]

Salt water in your pool had nothing to do with those issues.
You live in Houston. The environment is corrosive. You had natural degradation from the environment.