anaerobic zone in 4 in sand bed ??

[juliedealer]

I have a 4 in sand bed. The purpose of which is denitrification. The sand is directly on the tank bottom, will there be a dead zone without something to creat a 1 in space at the bottom?

[SaltyDog]

What size is the average particle of sand?

[juliedealer]

primarily, it is oolitic

[DSB]

I think that anerobic zones are generally considered to start at about 1/2" to 1" below the surface. Doug's page has a ton of references to live sand articles and discussion threads as well as many other topics.
http://sites.netscape.net/douglxyzzy/sandbed.html

[DougL]

juliedealer;

Depending on average particle size and water flow, the sandbed will become low enough in oxygen to denitrify within the first inch or two, with or without a plenum.
(the one inch gap on the bottom). IMHO, the plenum has no useful function that a similar amount of material placed directly on the bottom would not provide. The
plenum does however, prevent the use of small particle sands such as oolite, that can potentially have higher infauna diversity and biomass. Since the oolite simply
falls through screening, no gap can be maintained using oolite sand.

Hope this helps;

DougL

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