substrate decisions - dsb crashes

[wayne in norway]

Personally I'd go for a shallow sand bed in the display with a dsb in a sump or refugium setup. I have an upstream refugium. If it crashes I empty it and start anew.

Reefnutz - I was aware that both the bacteria for aerobic and anaerobic bacteria were aware in shallow sandbeds, however I kind of assumed that the amount of oxygen around simply made the reduction to nitrogen gas pretty much impossible. However I'm now starting to think that maybe nitrate reduction does take place in thin shielded anaerobic films as the reference suggests. I wonder if that is more likely to happen on the surface of static (live)rock rather than on sand grains that are commonly bumped around and the film disturbed.
Or maybe I'm just thinking trash.

 

[Unarce]

It's certainly feasible to believe that the nitrification/denitrification process is halted when the sand is disturbed. In my experience, only the small grains along the perimeter of the tank are potentially blown about. Having multiple grains sizes lessoned if not eliminated this possibility. Everything within and underneath the rock structure is protected and undisturbed by the current (but turned over by my cucumbers).

Another misconception is that the smaller the grain-size, the more surface area there is for bacteria. This would certainly hold true if we assumed that every grain was a perfectly round sphere. But, take into account the rough edges, crevices, and porosity of larger grains, then it becomes quite comparable.

Like many, I like the pleasing aesthetics of fine sand (which makes up most of my shallow sand bed). But, having multi-grains with the larger pieces turning into miniature live rock themselves has certainly added to the sand bed's functionality as well as its appearance.