For water changes, I age my tap water for 2 days to 2 weeks in plastic, one gallon jugs and the ph is 7.0 and the water is very soft and the kh very low. Is there any safe way to lower the ph to 5.0-6.0 before I use it or is a RO unit the only solution? As it is, I have to use alot of Malaysian driftwood to keep the ph down. Thanks.