Neutralizer media--also known by the trade name Calcite--will neutralize acidic water with pH levels as low as 5.8, bringing them up to a range of 6.9-7.2. Can be used in upflow or downflow filters. Must be replenished every 3-6 months.
Available in 1/2, 3/4 or 1 cu ft buckets.
If your pH level is below 5.8, you will want to use Neu-Cor instead.