Originally Posted by Dekz
Let some tap water sit in a bucket for 24+ hours and then test it. There are gasses and such that need to escape before the reading is accurate.
Dekz hit the nail on the head. You may find your tap water is this issue. That said you may not even have an issue. My fish thrive (even breed) in my hard water with a pH of 8.2 - 8.4. You may have just lost the fish due to pH shock or somthing else.
When you are stuck with a high pH (from your tap), just check with the store when you buy fish as to what pH they are in. If it's low pH then acclimate them more slowly. Most fish will do fine once they are used to it. As stated before, it's the large sudden swings that's bad for them.
I've learned about pH and these issues the hard way. Now it's a non-issue for me.