Janet,
All those things you mention are concerns I am trying to balance. I'm not sure I understand why I am losing so much chlorine during the day. I retested my night time loss again last night to be sure we aren't losing any at night - we put a jug of bleach in at around 9:30 to bring FC up to 8ppm, shut off the chlorinator (which we had put 3 pucks in earlier in the day and set it on low to try to bump up CYA to slow daytime chlorine loss), and tested at 11:00. FC was at 8.0, CC - 0.5. Tested this morning before the sun hit the pool (about 7 am) and it was still 8.0, CC - 0.5. We do get a lot of direct sun-light on the pool. We are in south central Kansas. The pool is a direct Southern exposure with the direct sunlight first hitting east end of the pool by about 8 - 8:15 am and the first shade hitting the west end of the pool at about 6 pm. That's nearly 10 hours of strong direct sunlight, and the last week or so has been in the 90's nearly every day, dry, and nearly cloudless. I have been assuming that has accounted for my continued high chlorine loss during the day despite stable FC levels overnight. I just ran another test ( it is now about 1 pm - so 6 hours after my last test) with the following results:

FC - 5.5
CC - tr
pH - 7.4
TA - 120
CYA - 50 ( I really have trouble reading that dot - but 3 different tests got the same result) (we did have to add quite a bit of water today due to evaporative loss - level was down to bottom of skimmers)

Pool is 19500 gallons "sport" pool - 18x36xaverage 4 foot depth (3 foot shallow end, 5 foot middle, 4 foot other end).

The other issue that puzzles me a bit is my continued tr-0.5 ppm CC - we have had it at shock level 2x since we stopped losing chlorine at night, water has been crystal clear for weeks now, but CC doesn't seem to change: usually just a trace during the day, 0.5 first thing in the morning.

Any thoughts out there?

Thanks again for being here.