Thanks for your reply. Yes, the pool has a (defunct) heater, the water is Suffolk County (LI) ground water (and somewhat original -- the pool was built in 1998), I have shocked it with 6 gallons of bleach, and my PH is pretty good right now (it usually needs a lot of baking soda when I open it up but this year, not so much). The pool is already clearing up, and the filter has taken care of the particles that were floating. It's weird -- the pool is the color it always is when I take off the LoopLock (blackish) -- it's just those particles that I am seeing for the first time and I don't think it is a coincidence that I converted over to salt last year (so, his was my first post-salt-conversion pool opening).