Deep sand bed

[Mickle]

I'm thinking about designs for my sump,at present I want a DSB, my heaters a skimmer, bioballs, return pump and a prefoam... The sumps 12x8x8

Now whats the benifit of a DSB, whats the best way of doing it and how big will it need to be to be effective? Are bioballs nessesary with the DSB?

Any advice is more than welcome

[Mr. Fosi]

Now whats the benifit of a DSB, whats the best way of doing it and how big will it need to be to be effective?

 

It allows for denitrification (NO3->N2 gas). I don't know the best way to do it, or how big it has to be to be effective. I do know that you are going to need at least 3" in sand to make sure that you have an anoxic layer in which the denitrifying bacteria can live. I have read of people making them as deep as 4-6", but that may be overkill.

 

Are bioballs nessesary with the DSB?

 

No.

[Mickle]

Thanks

Anyone got any insights into how it works?

As in, just section off a bit of the sump and put some sand in, do you have flow passing though etc?

Or would I be best setting it up as a refugium?

[Mr. Fosi]

Anyone got any insights into how it works?

 

It works just like every other part of the notrigen cycle, except that the bacteria that metabolize the NO3 into N2 gas are obligate anerobes; that is: they cannot live in the presence of oxygen gas. The reason they will inhabit a DSB is that just below the surface of the sand, the dissolved oxygen drops to zero.

 

If you have sand stirrers, your DSB will have to be deep enough that they won't stir the entire depth, otherwise you defeat the purpose of having it by reindroducing dissolved oxygen into the lower layers of the sand.

 

Here is a good flowchart from http://www.marietta.edu/~biol/102/ecosystem.html, too bad it was drawn to illustrate the terrestrial cycle:

 

 

As in, just section off a bit of the sump and put some sand in, do you have flow passing though etc?

Or would I be best setting it up as a refugium?

 

Either one. You would have to have some flow passing through it because you need to move water containing NO3 and carbon through so the denitrifiers have things to eat and build their population with. As for how much flow, I doubt think it matters. As long as you are not disturbing the sand to any depth you should be fine.

 

One caveat: I haven't ever done this in SW. What I have stated here was from what I learned in my bio and aquatic ecology classes during my undergrad.

[Mickle]

Thanks for the info!

Ok, do it wouldent be difficult to set up, but would it be worth it, or should I go with a refugium?

Or if anyone can tell me the size it should be maybe I could have both, but my sump is of nano proportions

[Mr. Fosi]

Ok, do it wouldent be difficult to set up, but would it be worth it, or should I go with a refugium?

 

You could conceivably do both at once: have the DSB in your 'fuge.

 

I don't know it if would be worth it. You may want to do a search on deep sand beds over at Reef Keeper Magazine. They may have some quasi-quantitative amount of denitrification per square inch or something.

 

Some people have noted that the sand in nano 'fuge DSBs can get really funky. In a nano, my intuition tells me that you will get more nutrient export out of a refugium.

[neanderthalman]

I was under the impression that you needed to have more than 3" of sand for the anoxic layer to form, and this was why many DSBs are closer to 5-6".

 

I'll bet that the coarser the substrate, the deeper it has to be to be effective. More water space between particles makes it easier for oxygen to diffuse down in there. 3" of sugar sand might be enough, but you'd need 5" of aragonite, perhaps.

[reefman23]

A DSB that is less than 6" deep and is only 12"x8" (max) wont be worth it...try a RDSB like this http://reefcentral.com/forums/showthread.p...25&pagenumber=1 ....very long thread, but great idea and works GREAT.

 

Jesse

[Mr. Fosi]

I was under the impression that you needed to have more than 3" of sand for the anoxic layer to form, and this was why many DSBs are closer to 5-6".

 

That all depends on the water flow and the amount and type of stirrers.

 

I'll bet that the coarser the substrate, the deeper it has to be to be effective. More water space between particles makes it easier for oxygen to diffuse down in there. 3" of sugar sand might be enough, but you'd need 5" of aragonite, perhaps.

 

You are certainly right about larger size meaning a deeper bed. A very fine sand should be completely anoxic less than 1" down, unless it is being stirred by something. Most people don't use just one type of sand, though.

 

From what I have read, most people use a mix of sand grains b/c the bed of course grains would have to be put down really thick and a bed of fine grains gets as hard as cement.

 

EDIT: The link posted by reefman is very useful and informative. It deals with the sand/cement issue as well as a great many other issues surrounding Remote Deep Sand Beds (RDSBs). I am thinking of trying one...