Got a question that ahs been killing me all summer. All my pool numbers have been pretty good except at begining of season my ph was high so added MA and its been right at 7.2 for a while. All numbers looks good as well. My main problem is every reading shows no free chlorine (0). I have been adding shock (it came with the pool that was built last year and no issues with pool maintance last year) till I get a reading of free chlorine. That lasts about 24 hours then back to 0. I have an automatic feeder that has been turned as high as possible. Remember this all came with the pool. The other problem is I have been fighting small amounts of green algae I assume due to no free chlorine. Please any help would be greatly appreciated. This is about 17,000 g pool.