I have been having this problem for over a month. My pool turned real green when I was on vacation. I used the things the local pool supply company sold me and it did clear the green up and some more things to clear up the cloudy water. Now when ever I test the chlorine it show 0. The pool supply kept telling me I have nitrates in the water between 1 and 2. They kept selling me shock by the case and telling me to keep shocking the pool. I have dumped over 50 pounds of shock in the pool and it stall will not hold chlorine and they say it still has nitrates. I have been doing some reading on this forum and I am trying to switch to bleach instead of shock and have purchased my own test kit. I can add bleach and get the chlorine level up to 5.5 first thing in the morning when I test it, but by noon it is back to 0. This morning when I tested it before day light it was at 7.5 and now when I test it 10 hours later it is back to 0.5. Just looking for any ideas why it will not hole the chlorine. Everything else seems to be within range and the water is very clear.
It is a 14000 gal above ground pool with a sand filter. Not Salt water.
Thanks for any ideas