When I test it at the end of a light cycle, it can be as low as 7.7, after a dark cycle, I have recorded 7.5 at times. I use an API test kit. I strive for 8.2, but can not seem to keep it there. Whenever I visit a LFS, I have them test it as well. Always, the comment is the same - low pH.
I don't see anything suffering, per se; but I am not knowledgeable enough to say whether or not things are truly "thriving". Though, I'd like to think so! I have been told that a higher pH will help to keep my Ca levels higher, too.