Well for example if you inoculate
Pseudomonas stuzerii into your tank it is a facultative anaerobic bacteria that can breakdown nitrate under microaerophilic conditions to nitrogen gas. Therefore just adding the bacteria without providing the microaerophilic environment will not lead to nitrate conversion.
I would still like to keep this thread on focus about nitrate because we really haven't finished where we left off (unfortunately I have been really busy with work lately and haven't been about to continue the discussion to date,
).