You rarely need to worry about pH in a planted tank. Both the plants and the fish will quickly adapt to whatever pH your water is. Trying to control the pH independently is a losing battle. Adding pH up or pH down substances does more harm than good, and adding "aquarium salt" just makes it worse.
KH is the important water quality measurement, for both fish and plants. But, even that has a wide range of acceptable values from near zero up to at least 6 degrees of KH. Sudden changes in KH are very harmful to some fish, so even KH is best left alone, as whatever the tap water or other change water makes it be, except in unusual conditions. Generally when you ask a LFS employee or owner what can be done about something, they simply think about what they can sell you to change that something, not about whether there is any reason to do so. Places like this forum are a far better source of advice.
Last edited by Hoppy; 08-10-2012 at 02:21 AM.