So I run a 22,000 SWG inground plaster pool with a DE filter and in SE PA, US. Current temp on pool is around 87F w/o heater on. I have found the forums here extremely helpful and LOTS of useful information. I am a chemist by training, so unerstanding all aspects of pool chemistry are relatively easily and have read pool school. Did have some green alge growth and a bunch of 9 year olds at a pool party 2 weeks ago, although Phos is only 300. I have been having trouble with FC levels, have followed SLAM guidelines CYA of 60 everything else balanced. Issue is I have low drop overnight, 1 PPM, but 8 hours later down to under 0.5 PPM. Pool is crystal clear, but still unable to hold a FC level anywhere near normal. Going on the 3rd night of reaching 30 PPM FC with liquid Cl, 10%. Any thoughts on my issue? Pool is only 2 years old, so could it be the cell in a Nature 2 system? Perplexed and frustrated at the issue. Want some insight before I make an investment into a new cell. Continue SLAM? Unfortunately can't be home during the day to monitor FC levels.