Hey experts, I'm just a lurker here waiting for it to get warm and stay that way! I was just reading through this post and saw the test result for CYA on 3/14 being reported at 80, and on 3/21 CYA being reported at 40.
That's not really "possible" unless there's been water replacement (which doesn't seem to be the case) so I'm wondering...OP, are you sure you are doing your CYA test right? It's a pain in the neck and has conditions like...make sure you do it on a sunny day but with your back to the sun and the tube at waist level etc. Otherwise the reading won't be accurate...
Personally I hate the CYA test. I just checked mine for the first time this year and it was easier than last year when it was new to me but it's still a pain....(mine's only 30, but beside the fact that the water is barely 60 degrees, I don't have an SWG which seems to require a higher suggested level of CYA)
Anyway, it's pretty important to have that right so I figured I'd chime in here just in case!
Oh and, your pool looks beautiful!!