I am in no way an expert, but I have heard baking soda does the trick. Unless you count that as a chemical, of course. I'm not sure how you're supposed to add it nor in what amount, but you might be able to Google it.
you could use peat in youre to lower the ph or to make it higher use baking soda or crushed coral sand, also some rocks make ph rise. changing ph in water is annoying and hard to keep at a constant level.
What are your current stats? (pH KH GH) and what do you want them to be?
Generally it's best not to try to change anything unless it's really neccessary. If you really have to, there are better ways to do it than chemicals but how well they work will depend on the water you have to start with.
I wouldn't change it. Messing with pH can be dangerous. Sudden changes can be more harmful than a constant, stable pH that is a little off the ideal reading. In your case, 7.0 seems about right for the fish you are keeping.