re: Baking soda as buffer

IF you take a look at the back of a bottle of Buffer-Up you'll see it's nothing
but sodium bicarbonate - baking soda.  I bought a bottle of Buffer-Up as a
paranoid newbie but never again. :)

How much to use depends on the present buffering capacity of your water.  I
think ~240 ppm is about right for most systems and each .5 tsp adds around 60
ppm per 10 gallons.  I'd suggest getting a test kit for carbonate hardness and
add and test, add and test until you get the level you want.  

Do dissolve the baking soda in dechlorinated water first, of course. :)