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What is the average depth of a new aquarium sand bed? I will soon be putting together either a 120 or 150g tank, but I need to know how much sand to get. Is 1 inch to little, is 3 inches too much?
 

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I have a 3" SB, perfect in my 180 gal with Diamond Spotted Gobies, Conches and Nassarius Snails. Stays white all the time as well.
 

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I have 3"...I guess I'm in "No Man's land" :confused:
 

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4" is about the minimum depth if you want the sand bed to function as a denitrification bed (DSB primary function aside from sinking phophates). Anything less and the bed will act as a nitrification compartment, with mostly aerobic and some marginal facultative anaerobic bacteriological activity occurring that drives nitrogenous substences mostly to nitrate. This is not to say that the sand at this depth is not without some function: it would be possible to have a well-designed system with little live rock in it that would be capable (depending on bioload) of handling ammonia-to-nitrate conversion without any problems. The rub comes when you want the sandbed to function as a denitrificaton mulch pile, as without the establishment and maturation of obligatory anaerobe populations, along with chained biocoenosi that convert the intermediate nitrogen compounds to usable substrates for these populations, there will be little if any denitrificatioin occurring in sand beds of less than 10cm, ESPECIALLY in tanks with good circulation near the substrate.

Keep in mind that there is little good closed-system documentation on this subject, most of it is either extrapolation of what happens in vitreo or on the biocoenosis of corals substrates in the wild. Depending on proximity to healthy coral stands, substrates may be either algal-driven or bacteriologically-driven egologies, much has to do with the nutrient levels of the interstital waters of those sandy substrates and/or the level of pollution and levels of current in these situations. For most of us keeping DSBs in closed systems, we have artifically high nutrient levels, and the systems are bacteriologically-driven much like those ecologies where nutrients levels in the wild are also artifically high. Keep in mind that these systems are not the norm in nature, and do not represent ecologies found in biotopes unaffected by anthropomorphic inputs.


Google some of Yuri Sorokin's or Alaina Szmant's work on coral/marine sediments and their bacterilogical ecologies.


HTH
 

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btw, very shalow sandbeds are easy to keep if they are kept shallow, vacuumed frequently, and not allowed to collect detrital eddies of nutrients. However, they will not lower your nitrates, and if anything, much like having a particulate filter in your water processing, usually contribute nitrogen as nitrates to the water column.
 

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Tom,

So are you saying one needs to have > 4" or BB?

I ask as I'm having to either stay BB or start a new sand bed. I moved recently and lost my sand bed in the move (long story). I had hoped to just need 1-2", prior to the move I had a DSB and the movers (a local store) went on and on about how DSBs were a thing of the past....

I've got a refugium with major DSB in it, but wanted some sand in the tank, or was considering it.

thanks,
Chris
 

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Tom - awesome DSB benefit explanation post.. that was the one I needed to read. :D I am going to give a 5" or 6" DSB a whirl...
 

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4" is about optimum if you want good nitrate reduction. It helps to have clams in the system along with the sand, as they suck up a good bit of the nitrates AND phsphate that occasionally are problems with DSB systems. Export whenever possible, and keep the rock off the substrate to allow for circulation and even O2 gradient depth. This also allows for easier detrital removal in these systems if your circulation is good enouth to keep accumulations from occuring under the rock (use rock stands).


DSB's are really good for lagoonal biotopes as well as to provide homes fr creatures that you desire that require DSB's to do well. I would not recommend them for systems geared towards reeftop biotopoes unless you are ready to commit to some husbandry schedues to keep exports high awnd inputs low. DSB's sometimes dune when circulation gets up to suspending speeds for detritus, so they may hamper systems with closed loops.
 

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wow.. more good info.. sounds like I might be in for some "husbandry" with my desire for both a DSB and a nice reeftop.. well, mostly LPS corals, but I wanted to be able to have some SPS corals too.. hrm.. I am planning on having very good flow also.. two return lines and two Seio M820s on a wavemaster pro in an 85gal.. should get things moving.. hopefully not too much tho as to start drifting on the bottom..
 

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tiburon said:
...planning on having very good flow also.. two return lines and two Seio M820s on a wavemaster pro in an 85gal.. should get things moving.. hopefully not too much tho as to start drifting on the bottom..
Try running a length of 1" PVC under the rock with a cap on one end and a MJ powerhead on the other end. Drill holes pointing up into the rock in sections under the rock piles to help move detritus and keep circulation under the rocks up for detrital removal. Don't forget to run your skimmer a bit on the wet side (which will require that you carefully monitor your salinity for gradual drops if you use automatic topoff) and to keep it clean to improve exports, very important with DSB systems. DSB's have a definite lifespan; export keeps it as long as can be expected.


HTH
 
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