Air bubbles in sandbed

[worm]

I noticed this morning that i have small air pockets in the top inch of my sand bed. is this some types of nitrogen exchange? i'm about to do test on nitrate and such.
my sedbed is 4" deep. i had about a 2" sandbed for 8 months. when i moved 10 weeks ago, i added an additional 2" on top of it.

 

[jonthefb]

the bubbles are more that likely the bacterial colonies workign hard to process your nitrogen. There is always a slim possibility that they are air bubbles trapped from adding the new sand, but i would leave them, as they are probably bacteria.
good luck
jon