[al404]

in realtà quello che dicono è che non è vero che serva per forza la zona anossica, il post è proprio dedicato al DSB
commento 259
http://www.reefcentral.com/forums/sh...268433&page=11

tmz dice

"Deep sand beds lost some of their allure a a biofilter , when I realized the bacteria performing denitrification are facultative heterotrophs. They live in the presence of oxygen and when they exhaust it in a given location they turn to nitrate for it facilitating the formation of N2 gas from some of the freed up N which exits the tank. If there is left over organic material and both oxygen and oxygen sourced from nitrate are exhausted,sulfate reducing bacteria take over.
This means denitrifying bacteria can do quite well in shallow sand or even on bare surfaces . They even create hypoxic conditions in their mulm where anaerobic activity occurs;ie, using the NO3 for oxygen. So, denitrification via assimilation of dissolved nitrogen as these bacteria grow and nitrate reduction to N and N2 occurs in the top half inch or so of the bed. Not much happens down deep for denitrification since these heterotrophic bacteria need a source of oxygen organic carbon, nitrogen and phosphate to grow and not much moves down there via diffusion, a relatively weak force or even advection a bit stronger but still inadequate force. Not much organic carbon,oxygen, nitrogen or phosphate will get down there fast enough to encourage much deitrification; nor much worry about sulfate reducing bacteria taking over and producing H2S since the sufat reducers need the organics too. In fact ,ime, you can find just as much evidence(black sufides) of anoxia and sufate reduction activity in shallow beds of an inch or so asanywhere else.

Overall, a shallow bed reduces nitrate a about the same rate as a deep one since the action is near the top where the nutrients are. Thus , the choice about a sand bed is more a preference than a case of a good method vs. a bad one,imo "

leggendo il profilo non mi sembra un novellino

in un altro punto ha linciato questo articolo, ma sinceramente mi son perso
http://www.advancedaquarist.com/2014/5/chemistry