breeding is the only time you should ever consider changing the water chemistry. peat works well as it actualy acts as an ion exchange resin and removes calcium from the water, while driftwood will not decrease hardness but will drop the pH via realese of tannic acid. However both of these things will give you upwards swings in pH when you do a water change though and the only way to supply the appropriate hardness water for your change is to run it through peat before it goes in the tank or use a Reverse osmosis unit