Quote Originally Posted by Yeggim View Post
Sometimes the testing times will influence that overnight loss number. With low CYA, testing a little too late after sunrise or a little too early before sundown might account for that extra 1ppm. What's your CC numbers?
Interesting you should say that - I was worried about going too far the other way. I'm testing at 10pm, so the sun is well down, and 6am (which, frankly, is a pain) so that the sun hasn't been up too long. Up at 6 again tomorrow - will post CC numbers then...