How long before bacteria die from drying out?

[Marconis]

Let's say you're doing a water change, and your HOB water flows back out the intake. You know how your media is exposed to air? How long does it take before the bacteria die off without water? I usually fill it up with a cup of tank water within thirty seconds...I wonder if that does harm.

 

[fort384]

If the media is still wet, the bacteria will be fine.