Baking soda is fine to use. It can initially lower your ph when you add it so don't add too much at once. To avoid that some people use washing soda (sodium carbonate instead of sodium bicarbonate). But don't buy washing soda because it isn't food grade and you may get some unwanted impurities. Instead you can just bake the baking soda at ~350F for an hour and that will change it from sodium bicarbonate into sodium carbonate.

Here's a nifty calculator that will give you the amount to use for either baking soda or baked baking soda...
http://jdieck1.home.comcast.net/~jdieck1/chemcalc.html