A pH drop is most often (although not always) facilitated by insufficient buffer capacity. Crushed coral takes care of that on a sustained-release base. While this is very comfortable and low-maintenence, it allows fluctuations when you change water. Check your hardness, and you may be best off with an additive that increases kH and gH instead of messing with pH adjusters. Basically grab the problem by its roots ... and some crushed coral might help you in the long run.
Good luck,
HarleyK
