What is your tap ph?
What is the ph you are trying to get in your tank?
Certain rocks such as limestone (Texas Holey Rock) and substrates (crushed coral) will keep your tanks at around 7.4 - 7.6 without adding a thing, especially if your tap is above 7.0 .
Baking soda is the item that you would want to use if you need to increase ph.
Baking powder contains sodium bicarbonate (baking soda), but it includes the acidifying agent already (cream of tartar), and also a drying agent (usually starch), these are the items that you want to use to puff up your cookies and cakes.:lol: