Well day 2 after determining my cloudy water was algae [go figure ..rainy season in a hot tropical climate] due to oclt. Went from fc 20 to 11.5 overnight. So yesterday I started slam and got a little overboard with the powder chlorine [that's all I have to work with here at moment [inherited pool and 20kilo tub of pro powder chlorine]. I tested fc 28 [approx half cup added to 4800 gal pool] at sunset. Woke up just tested fc 26.5. Water already looks a little clearer yay!. My cya is currently 50 [ was 40 prior from 80 as I had drain half the pool] so this 20 kilo pro chlorine powder must be the type that contains cya conditioner. Will keep a close eye on it.
Thought I would just post an update.
Thanks again for all the help everyone!