Nine months to get your pH stabalized at 8.2 ???!!! <img src="graemlins//eek.gif" border="0" alt="[eek]" /> WOW
That's funky !
I may buy into the fact that using pure sodium bicarbonate baking soda may help raise your alkalinity over time, but you are only adding sodium bicarbonate, not all of the components necessary to maintain alkalinity.
Also, going from a pH of 7.5 to a 8.0 in a 12 hour period is drastic to say the least, providing you are actually measuring the affect of the baking soda, and not reading a typical day to night pH shift.
pH is not measured in ppm, but is a logarithmic scale from 0 to 14.
Jumping from pH of 7.5 to 8.0 in a 12 hour period is a fairly large induced pH jump in my opinion, and I feel may certainly cause some degree of pH shock, or at least some unnecessary stress to those that live in that tank, if done incorrectly - ie OVERDOSED.
But it would be in line with what has been discussed above regarding a dramatic rise in the pH .
Sorry dude - I'm still against using it as THE only method to control pH and alk. I'm not being fooled because it is cheap - I'm just not a fan of using it for my reef tanks.
If not done correctly - baking soda by itself can whack out your tank water faster than you can say Arm & Hammer !
Aside from lighting and food, I try to take care of my water and let the critters more or less take care of themselves.
My view