Purging sand

[asylumdown]

So I know there's different ideologies on dealign with sand beds, but not so long ago I got the bright idea to turkey baster my sand. My logic was a) I have no siphon vac and I never siphon water from my display so I wasn't going to do that and b) my sand was getting disgusting from where I could see it through the glass, bubble algae was actually growing BENEATH the surface of the sand, cyano was starting to cover it, dinos bloomed and faded on it on a regular basis, all while my rocks were algae free and my corals were growing like gangbusters. I figured there must be something in the sand that was feeding the algae that wasn't making it in to the water column, so I decided to turkey baster the heck out of it to hopefully fluidize the gunk so my filter socks and skimmer could suck it out.


Fast forward about... 2 months? I've now done it three times (tonight being the third). I've noticed that in the sections where I've done a thorough turkey bastering so that all algae of any kind is completely removed and the sand looks new, I'm seeing TONS of bubbles forming inside the sand against the glass. Sometimes as shallow as 0.25 inches below the surface.

At its deepest, my sand bed is maybe 3.5-4 inches, and that's only in a couple of spots. I didn't think that was deep enough for anoxic denitrification, and I certainly didn't think you could get denitrification a quarter inch down. Are the bubbles I'm seeing nitrogen, or O2, or CO2?

Further more, the bacteria that do the denitrification, are they a specific group of anaerobic-only species, or are they also facultative anaerobes that will consume oxygen if it's present, but switch to anaerobic consumption of nitrate if O2 levels fall too low? In the former case, I'd be torpedoing any denitrification potential my sand bed has by blasting with a turkey baster and fluidizing everything, but in the latter case denitrification should start up again within less than a day of disturbing it.