Quote:
Originally Posted by
KoiCop 
Bio-conversion produces carbonic acid which is buffered (think: neutralized) by KH. Once the KH has been used up, continued production of carbonic acid will cause the pH to drop. Allowed to proceed unchecked, eventually the koi will suffer from acidosis then die, and so will the bio-bugs. Game over.
With a decent source of water, and sufficient water changes, KH will be continually replenished; therefore, there's no need for most folks to add baking soda to jack their KH through the roof.