Thanks Casey, I bought some chemicals 5 litters of liquid chlorine, Alum 10 Kg, 30 Litters of muriatic acid and potassium permanganate 200 grams.
My test results as follows,
FC - 0.5
PH - 6.8
TA - 40
Copper - 0.1
I bought liquid chlorine to shock the pool as the chlorine level is low, and I can feel the algae in the vinyl liner. Pool is under the hot sun for couple of days with low chlorine.
Local pool supplier said I have to use alum to clear the green colour, and the chemist said I can use potassium permanganate to remove the metal (I am not sure of these and looking for help here)
Tomorrow I am planning to buy CYA and try if I can buy phosphonic acid, even if i buy I am not sure how much I will need for 55,000 litters pool. May be I can take a sample of 20 litters of pool water and test with phosphonic acid but not sure about the method.
Note: The pool became clear yesterday as the chlorine evaporated, and added 1.5 litter of liquid chlorine and it turned again green but this time it is not as bad as the last time.
I have also ordered the not iodine salt which will come in two days, after that I am planning to start the swg for chlorine production.