I'm guessing by reducing acidity, you want to lower your PH.. Baking soda does the oposite..
"Raising pH
It's not often that the pH must be increased, as most water sources are already slightly to moderately alkaline. In the event your water is acidic, and you want to keep fish that originate from alkaline water (as is the case for certain Cichlids).
Filtering the water over crushed coral is the method of choice for raising the pH. The use of limestone rocks in decorating the tank will also raise the pH, but keep in mind that you will not be able to adjust it readily.
The addition of bicarbonate of soda (baking soda) will also raise the pH and has the added benefit of buffering the water. Keep in mind that this will be an ongoing thing, so you can't add it once and forget about it. "