My water is acid!

Okay, I exaggerate, but I ran a Nutrafin Wide-Range test and my the ph was around 5.5 to 6.0 range, which I'm pretty sure is horrible for goldfish. I ran it again on my tap water and it was also 5.5 to 6.0 range.

I'm going to start slowly putting in some Alkaline Buffer I have, but I'm worried that every time I do a water change (which I do once a week) its going to wipe out my efforts since my tap water is so acidic.

Any advice for me? Maybe the test is wrong, or can I put something in my tank that will constantly reduce the acidity?