Tips for raising and lowering your PH
Lowering pH - making water more acidic:
Filter the water over peat.
Make a partial water change using softer water. You can use rain water or water prepared by boiling.
Add bogwood to the tank.
Use a commercial pH minus (acid) buffer.
Raising pH - making water more alkaline:
Aerate vigorously to expel carbon dioxide (CO2).
Filter over coral, crushed shells or limestone chips. Add calciferous decor to the aquarium such as tufa rock or a coral sand substrate.
Make a partial water change.
Use a commercial pH plus (alkaline) buffer.
Any change to the pH should be undertaken gradually and particular care should be taken when using a commercial pH buffer. Often they create a rapid pH change and cause the fish to suffer pH shock. I recommend preparing water in advance and adding it slowly, perhaps during a water change.