Slight correction....baking soda is sodium BIcarbonate while soda ash is sodium carbonate. By "baking" baking soda, you drive off carbon dioxide producing soda ash.All Soda Ash is, is actually Sodium Carbonate. So basically baked baking soda. You could go to the grocery store and make your own Soda ash.
How much cheaper is it? I know it's an expensive hobby so every dollar counts, but brs sells the gallon supply for <$8. That lasts me months in my 120g. Why risk it? Just use something food grade or labeled "aquarium".Thanks everyone.. I know the difference between sodium carbonate and bicarbonate but I was wondering if the pool supply chemical was "clean." is there really any difference in quality or is all sodium carbonate the same?