Hook up your skimmer. That will aerate your water, which will increase carbon dioxide. most high pH situations encountered are caused by a carbon dioxide deficiency. Normal air from the room contains some CO2, so that should help.
Are you using any additives? And is your tank heavily planted? Plants and algae will drive down CO2 in your water through their respiration, thus increasing ph. (That's why ph normally drops at night, when photosynthesis of plants and algae largely ceases.)
Just a few thoughts!