Use some acid buffer to bring it down to where you want it, make it match the tank pH as best as you can to avoid a fluctuation. Test, adjust, retest - over and over till its right. There are some commercial neutral buffers you can use as well, just measure and add it and mix and it should do the trick.
Do a test before you add anything to your tap water. Many municipalities use soda ash to buffer the water so it will not leach lead out of pipes if there are a lot of older homes in your area. Once the water comes in contact with air the pH will drop right back down to 7.
Draw some tap water and leave it sitting for 24 hours, or maybe even just overnight. Test the pH to be sure this is your actual reading.
If this is the true natural state of your tap water, consider keeping African cichlids. African keepers go to great lengths to achieve this kind of buffering, and the fish would be in heaven.
A forum community dedicated to Aquarium owners and enthusiasts. Come join the discussion about collections, displays, product reviews, accessories, classifieds, breeding, health, behavior, housing, care, and more!