This is weird: for as long as I've lived here, the pH of my tap water has always been 8.0. However, I tested it today (I check it periodically just to make sure) and it's dropped to 7.4. I checked the tank, and that was 8.0. I checked both again with a different brand test, just to make sure my kit wasn't playing up, and yup: 7.4 and 8.0 respectively. I did my weekly 50% change, tested the tank again and it's 7.8, which I'd expect from mixing two different pH levels. I imagine the pH has risen in the tank over a week because my KH is really high (just over 300) so it's probably buffering it back up.
So what the heck is that all about, and what do I do about it?
I'm going to call my water company tomorrow and find out why it has changed, but that isn't going to help my poor fish deal with a swinging pH level. 
Thoughts?
