Hi , I am new & have a couple of questions. I have a 30' Round 21,000 gal. Vinyl pool that I have owned now for almost 10 years. I have a Hayward 1.5 HP pump and 18" Sand Filter. I opened my pool last Sunday (later than usual) and it was of course Green with the tadpoles included. I got rid of the algae but could NOT get the PH or Alkalinity right. Went and had water tested yesterday at the pool supply ... Chlorine level was practically nothing, PH was too low...alkalinity was at 30 ppm...Calcium was at 70 ppm and CYA was at 184 ! I drained over half the water and am in the process of refilling now. It is going to be 97 degrees for the next 4 days...I have the pump running 24 - 7's. Do I need to add any bleach or liquid chlorine while pool is filling? I use well water and my pool only fills an inch an hour so will take a considerable amount of time to fill. After it is filled what is the first thing I need to adjust? PH? and then what next? I started using baking soda and borax 2 years ago but still stuck with 3" chlorine tabs as my main source of sanitizing for the simple reason of not knowing how much liquid bleach to pour into that many gallons of water. It tried the bleach two years ago but could never get enough in the pool to be right. Any help would be appreciated.