Newb Fighting Algae

[joe7670]

After firing my pool guy cause I was still getting greenish spots on the walls, came here and ordered test kit and have been monitoring my pool and adding cholrine as needed. Issue is my walls are still getting worse and the floor is turning color too.
Pool is 18000 gallons with diamond bright finish located in Miami, FL.
Readings are as follows for different dates:

8/30
fc 4.5
cc 0
ph 7.2
t/a 60
ch 460
cya 50

9/3
fc 3.0
cc 0
ph 7.5
t/a 60
ch 410
cya 40

9/4
fc 5.0
cc 0
ph 7.5
t/a 60
ch 420
cya 50

9/13
fc 1.5
cc 0
ph 7.5
t/a 80
ch 470
cya 50

9/16
fc 5.5
cc 0
ph 7.5
t/a 70
ch 420
cya 40

Why does this green stuff continue to show up on the walls. What am I missing. I keep adding chlorine to keep the FC correct and have added tabs to help keep the cya. Adjusted the ph to 7.5.

Would having the T/A a little low cause this?
cya 50

 

[JasonLion]

Do the spots on the wall brush off or do they stay there even when you brush?

If they brush off then they are probably algae. Your FC isn't high enough to kill algae that has already gotten started. To kill off growing algae you need to bring FC up to 16 and hold it there by rechecking the FC level and adding more chlorine to bring it back up to 16 several times a day.

If they don't brush off then they might be metal stains. Try gently rubbing them with a sock with a few crushed vitamin C tablets in it. If that takes off the stain then it is a metal stain and will need something like an ascorbic acid treatment and sequesterant.

 

[joe7670]

When brushed some of it comes off. Some of the thicker ones stay on.

I also took one of those thicker spots and scrubbed it with a sock and Vitamin C and it went away.

What approach should I take?

Also, in the case of algae. Once you kill it what should I keep an eye out to avoid getting the algae again?

 

[JasonLion]

Curious. Metal stains are not usually affected by brushing. Now might be a good time to read up on the ascorbic acid treatment and hopefully someone else will come along and comment on your situation.