i personally wouldnt mess with it. Obviously, depending on what lake theyre from, the ph would be a little higher naturally, but when you start messing with ph, youre headed for problems. You could add crushed coral which would buffer it on up to the 8.0 range, but if you do more than a 20%
pwc, which if yours are like mine a 50% is needed every week, then you have to treat the water before putting it in the tank so that you dont cause a big drop in ph, killing the fish. my tanks all run at 7.8, which is the same as my tap.
IMO, its best to leave it be. Anything between 6.5-9 is fine as long as it is stable