My tap water ph was 8.2 (well water) Using an acid buffer like seachem might work for you, it did a bit for me, but it didn't change it much. It also didn't bounce my ph around. (edited to add: PH DOWN don't know who makes it, but if that is what you are using it is junk, it did nothing for my 5G at all so toss it.) Every water change I used it and kept my ph around 7.9, but using a mix of distilled and treated regular water also worked wonders for my tank. It is now a stable 7.4 so if you go the distilled route make sure you mix it with your tap water.
When I do my changes I mix 60% distilled and 40% tap of the total quantity of water I am changing. My tanks are a 5G and a 10G so my water changes are not big. So there is still the tap water which has the minerals and stuff I was told I needed and the distilled being a neutral.
I was going to use peat but was told that it wouldn't be easy for a beginner like me to keep stable.
FYI I was told that a high ph is OK-ish but over 8 unless it is a fish that normally tollerates that ph it might do more harm than good even if it is a stable ph. 7.0 -7.6 is the most desired ph so i have heard and almost all fish will adapt to that ph.
If you do go the distilled route do it gradually so you don't over do it but was told once a few water changes go into the tank the desired ph will be easy to maintain.
It worked for me...
GL
Hugs
Jenn