Besides changing your whole substrate, and adding corals or crushed coral to tank..... I put crushed coral in a nylon bag, and drop in a section in the canister filter...
if PH is low from tap, You pretty much gotta add something buddy.... Like ashley said, I use baking soda, 1 tsp per 5gal bucket... works pretty easy for me this way cause when i do a water change, I add 5 gallon buckets at a time.... Really easy to put a tsp of baking soda, and 1/2tblspn of espom salt to each bucket.. this keeps the PH between 8 and 9, and keeps my water very hard, just the way my Tanganyikan cichlids like it!
moving you over to water chem topic, should get more responses there.