<a href=showthread.php?s=&postid=12455647#post12455647 target=_blank>Originally posted</a> by greenbean36191
I wouldn't assume they are N2 or H2S (especially not the latter). If you have hydrogen sulfide forming in your sand then you have a problem. If it's bubbling out then you have a huge problem. A properly functioning DSB will form nitrogen and you often see it as bubbles under the sand, but it's not that common to actually see the nitrogen bubbles coming from the sand. Usually the bubbles people see are oxygen bubbles formed by photosynthesis from the algae and cyanobacteria that are ubiquitous in the sand. The easiest way to prove to yourself that they're O2 is to watch during different periods in the lighting cycle. The bubbling should increase as the day goes on and the water gets more saturated with O2 and then at night there should be very little bubbling.