I used this after doing a water change in the hot tub. It’s about 2000litres, I still added some PH and alkaline etc but after putting this bottle in and then testing the water a day later it was perfect across the board. A month later the water is still super clear, no chemicals smell and all I’ve been doing is shocking it once a week and adding the little chlorine pucks.
I bought more bottles to add in on a monthly interval.