Do not use baking soda - it will raise your alkalinity, and you don't need that. If you want to raise your ph you use borax. If it were my pool, I would leave the ph where it is, turn the return jets up so the water bubbles on top - this will raise your ph while lowering your alkalinty. You can continue to lower the alkalinity by bringing your ph back down to 7.2 and continue aerating the water. This is the process to use to bring the alkalintiy down. Continue till you get your alkalinity down to 120. After the ph gets above 7.4 the aeration won't lower the alkalintiy anymore. If you have any other questions, please ask.