What is the brown spot? looks like it is growing but all chemicals OK. I think we have some water under liner. Shallow is concrete bottom. Is it possible for mold to grow through the liner?
Please put your pool specs on your signature. How does it react to brushing? If it plumes into a little cloud when swept and returns to the same spot It's probably algae. Also what are your water numbers
FC
CC
CYA
PH
TA
Ok, time to SLAM - Shock Level And Maintain the pool and brush regularly. If you want to keep the FC level a little below shock level so you can keep swimming that is fine. I did and it is much easier and cooler for me to brush when in the pool.
Oops, just noticed that CYA is 150. That is going to take a LOT of bleach. With 150 cya you should keep FC at 18 at all times and never let it drop below 11 to keep the pool sanitized and algae free. Shock level is 59 ppm. It will take 24 bottles of 8.25% bleach to take 36k gallons from 5ppm FC to 59ppm FC.
The best bet would be about a 50% drain and refill.
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