How deep the Fuge bed?

I am planning the layout of my fuge and realized that in all the threads I have read here about fuges, I have not seen a discussion of media depth. I saw references to DSB in the fuge, and about the need to chage them out every so often. If I have macros in the fuge to reduce nitrate, do I need a DSB? My thought was to put 1 or 2 inches of PremiumAquatics Grunge (sand, silt, rock chips, and usually some critters - from their curing tanks) some live rock pieces probably about 10 lbs.

Made from a 29G tank

Floor area of the fuge will be 12x20 - 240 sq. in.
Depth 14" - 3360 cu. in. or 14.5 gal

Inlet and return spaces will be about 6 gal for 20 gal working, 9 gal safety

 

It is all about what you want I only have 2" in each of my Fuges and mostly micros and a little rock and critters

 

I'm looking mostly nitrate reduction and Pod production. Considering Chaeto for macro.

 

heres where my idea of a remote dsb comes into play my fuge is being run seperate from my sump and will prob have a 6 inch dsb but the advantaage to my setup is i can shut it off completly from the main tank and completly dispose of it if the need arrives this way if the dsb doesnt work out i can try plenum and if that doesnt work out i can try bare bottom and if that doesnt work out i can try a xenia bed the options are limitless and i can always seperate it from the main tank at the first signs of trouble

 

Shallow beds say 1-2" still provide denitrification. The assumusion that we needed 4" inches of sand to provide denitrification was not the case. The majority of the baterial denitrification happens in the oxic/anoxic interface and in the oxic zones just under it. Avoiding deeper bed you can for go anerobic zones and therefore avoid many the the DSB issues. Such as crashes and hydrogen sulfide releases. Deeper beds do provide more habit for sandbed creatures though. The remote fuge you can turn off is a good idea to.

 

Hmm, now I gotta go do more research...

It has always been my understanding that the nitrate--> nitrogen gas bubbling out of system was performed in an anaerobic zone, like you mention. But that zone could only be achieved, in a functional capacity, at a minimum of 4 inches of sand (some say 6 plus inches...)

Covey, do you have links to newer articles regarding this (or older ones..whatever!) I have not come across these yet. The shallower sand does indeed affect the ammonia-->nitrite--> nitrate steps of denitrification...

I need to follow up on this... ;D

 

Yeah I am going to have to dig the up. Info was out of Reefkeeping. It was one or more articles by Ronald Shimek. Check back later I will go find them.

 

All right here the quote I was quoting.
"Second, most aquarists using live sand beds believe that top aerobic (oxic) layers overlay the anoxic layers where denitrification takes place. However, denitrification can also take place in oxic areas, and some of the highest rates of denitrification have been found in the top 1 cm of sediments where nitrate and oxygen levels are highest (Oren and Blackburn 1979). Denitrifying zones can occur from the top millimeter down to 10-15 cm or more."

And the link
http://reefkeeping.com/issues/2004-11/eb/feature/index.php

I also seem to remember a "Coral" story about it but since it is a "Brick and Mortar" MacKenzie it is taking a little longer to find. Anyway I can say with complete certainty that my 2-3" sandbed still denitrifies like crazy.

 

It is not that the anaerobic zones don't finish the cycle. They do from what read it is a different set of bacteria and a different process. I am still in the camp that believes that even the deep bed are not a hassle. Micheal you could set up a plenum since your fuge space is the standard size for a 10g undergravel plate. UG plate some plastic screen and 4 inches of the "Special Reef Grade" sand and you would have a nice plenum setup.

 

Thanks for that link...hmmm. Interesting.. not specifically referring to our sandbeds in the tank (as there is lack of real scientific data) but to the sand in the ocean, where real hard facts have been collected as to the denitrification in as little as 1mm of sand... food for thought, for sure! ;D