I think you can use peat moss in the filter to lower ph. I have never done it, so hopefully someone else here can provide more details.
I think you'll get this as a common answer from everyone here, don't mess with the pH, its much better to have a stable pH than to have one that's fluctuating all the time, the fish will get used to this higher pH as being normal and won't be stressed
Cool. makes sense
JMatt1983 is right. Unless you are breeding fish like discus, or your fish are wild caught, they will probably be fine if properly acclimated to your ph.
HI tb19, you have posted this question a couple of times, but you haven't said what your ph is. Have you tested it? There are three things you can do, that are "natural" #1 use driftwood in your tank, it should bring it down some, but how much is not certain, and every time you do a water change it will fluctuate up and down. #2 is to use peat in the filter. This also is very uncertain, as you have to keep a close eye on it and be sure to replace if the ph starts coming back up. the third thing is to invest in an RO filter system, to filter all the water you put in the tank, this will bring the ph down significantly, and this is what folks do that want to breed or keep really healthy discus.
But that said, I agree, most community fish can adjust to any ph under 8 and it would be better to leave it alone.