you don't give numbers for gH and kH so giving advice on how to lower it is difficult. my initial advice is to do nothing. your water is very likely just fine the way it is out of the tap and messing with the chemistry almost always creates an instability which is far more injurious to fish than a 'high' pH or hardness.
understand too that while elevating gH, kH and pH of water is easy, lowering it is very difficult. typical "hard water" contains calcium and magnesium salts which exist as carbonates. carbonates in solution exhibit a phenomona known as "buffering". when an acid is introduced to a water sample containing carbonates, the carbonates react with the acid and neutralize it, releasing carbon dioxide and a small amount of heat. the CO2 is exhausted at the water surface and the net result is no change in your pH.
simply put, carbonates stabilize the pH as long as they are present in sufficient amounts. when the carbonates become depleted, the pH of your water will plummet rapidly with the introduction of even a small amount of acid, killing fish, plants, and your biofilter. moreover, the chemicals sold for "adjusting" the pH of your water are typically but not necessarily acids of phosphate. they can effect an abundance of algal growth.
while peat can work to lower pH, it's impact is temporary and can be less significant if your kH is very high. driftwood is practically worthless in a very hard water situation.