Hi, I have a 55 gallon salt water tank I am learning to maintain on our own, the PH level was low at one time, so on the advise of an experienced tak owner, we brought the PH up using baking soda. Now the PH has creeped up to about the 8.2 to 8.4 level. We now have to lower it. How do we go about lowering it without completing a water change? Thanks!