Thought I'd add that it's a good idea to find out what the ph is wherever you buy your fish from. I don't bother to ask most of the time but it's a nice way to have some peace of mind for those 'spensive fish. One digit difference in ph means 10 times more or less acidic or alkaline, two digits apart means 100 times, i.e. if your ph at home is 7 and the ph at your LFS is 8 then the water at your LFS is 10X more alkaline than your water at home. Not good even if you float the bag half the day and trickle your tank water into it slowly IMO.
Mings post said it best. This isn't about what ph a fish can tolerate, it's about abrupt ph swings, a potentially deadly thing!