Deep Sand Bed

[Sye Davies]

in my proposed sump im planning to have a dsb with cheato.

im planning on it being 2ft x 20in x 7in deep (well the depth could be more if i wanted it to be.

my question is thus, how much filtering capacity will this give me?

the overall tank vol should be around 180g, i dont really want tonnes and tonnes of rock in there but obviously need a good amount for filtration.

what im trying to work out is how much rock as a minimum would i need with the proposed sand bed.

any thoughts/experiences would be appreciated.:)

[Glenn@home]

The requirement for flitration must surely be a function of the load placed upon it rather than the volume of water i would think.

So if you dont want loads of live rock then dont have a high bioload.

In terms of how much filtration will your DSB give you, im not sure that can be answered in any meanigful way.

FWIW a DSB is much more complex in reality than simply placing a load of sand in a container and passing water over it. I have seen many comments about the areaof a sand bed needing to represent a signficant protion of the tank area but have never seen anyone say that if the DSB is x, then it will serve a tank of y area.

I have seen those kinds of concepts used for cannister filters as an example though.

Out of interest what made you pick those dimensions for your sand bed?

As a rule of thumby i would suggest that the sabd bed should be as big as possible in terms of sirface area since this is where the exchange of nutrients will take place.

Im not sure having a sand bed 7" deep will compensate for having such a small surface area.

JMHO

Glenn

[Gavin Smith]

Anthony Calfo suggests that remote DSB (DBS in a bucket) are highly effective at de-nitrification.

Try looking through the marine depot forums for more information.

Apparently something like a swing bin (deep but small surface area) could de-nitrify huge display aquariums.

[Sye Davies]

thanks for the reply glenn:)

i had a sneaky feeling any answer would be in that sort area.

the dimensions of the bed are purly space reasons......thats all i can have.
the depth wasnt really trying to compensate for anything, merely ive read of some beds being up to 12" deep, if i can have a slightly deeper bed then why not was my original thinking (i can of course be pursuaded:D )

my proposed stocking list is on the high side so it would appear a large volume of rock is required.

so what your basically saying is plan the tank as normal regarding filtration.
a dsb is merely a very useful addition to it and not to be relyed on as a means by itself.

[Sye Davies]

thanks gavin:)

i will do some mooching about;)

[Gavin Smith]

I think in this case a DSB is exactly as simple as a load of sand in a container. All you want is a medium for denitrifying bacteria rather than the complex orgnisms of a fuge/dsb.

You pass water across it as quickly as possible without disturbing it so the detritus doesn't settle and you avoid the nutrient sink.

http://forum.marinedepot.com/Topic20039-13-1.aspx

Mine was pretty simple. I stopped using it due to space/kitchen re-organisation but will be setting it up again on my larger tank.

http://www.ultimatereef.net/forums/showthread.php?t=175415&highlight=remote

Gavin

[Glenn@home]

I havent seen that cocnept before gavin sounds interesting.

I have seen negative comments about DSBs of limited area since the inhabitants of the DSB whihc help to keep it active and clean often seem to need surface area rather than depth.

Sye, no i wasnt trying to suggest that a DSB is a kind of afterthought, only that the capabilities of the filtration in total govern what can be kept in terms of bio load.

When i think of filtration i should realy use a term like waste management or something like that, because water changes can be part of the control over waste too.

A point worht making though is that denitrification is only part of the story with DSBs. Denitrification relies of the provsion of a anoxic area for the delevopment of a suitable population of denitrifying bacteria (i think thats the right term, low oxygen area).


This can be achieved with what might otherwise be a sterile sand bed, how effective long term this would be as part of a total mamnagaement system is open to question.

Those DSBs whihc seem to offer the best long term prospects IMHO are those whihc incorporate the habitats for a range of micro fauna.

My DSb was 3x1x0.5 feet of playsand. When i pulled it out to break the tank down these was very little life in it at all under the first inch or so. Although there could have been bacteria and microscopic life it wasn as obvious as i have expected.

HTH

glenn

[Glenn@home]

ROFL Gavin and I have taken almost diametrically opposite views on this, just goes to show how life is never simple and there is no simple answer.

Glenn

[Sye Davies]

indeed:eek:

what it does though is make very interesting reading for me and stimulates my grey matter (no mean feat i can tell ya:D )

thank very much for the input guys (espesially the link gav) its better i consider this stuff now before i go and set it up and then change my mind:rolleyes:

[simon garratt]

Just a quicky.:)

So if you have no detritus/food feeding the bed 'only chemical', and consequently little to no life above bacteria to constantly break the sand structure apart, how do you prevent gradual glycocalyx binding and eventual suffocation of the lower layers to the degree the bed isnt actually doing anything at all.?

FWIW ive seen beds with little to no life solidify in this manner in just a matter of 6 months or less. even with a high flow, detritus of small partical size still impregnates the bed to a degree and gradually reduces exchange perameters.


Not rubbishing the idea, but to me the 'theory' just dont add up to the practice imo. Thats unless theres more to it than just a bucket of sand.

Which as Glenn says, There usually is.;)

I need to do some digging around to see exactly just how viable this method is in terms of longgevity compared to other methods, becouse as i see it at present, its quite easy to get round the nutrient issues with a wide shallow DSB bed with annual segmentation and replacement by strip if need be. But with a narrower/deeper bucket desighn, its not as though you can replace a section easily if need be should it become clogged/solidify, without ripping the whole darn thing up and starting again, which to my reconning is the last thing you want to be doing with an established system.


regards

Si.:)

[Gavin Smith]

I don't know is the answer.

I took mine off after a couple of months but may put one on when I get a larger system with more space in the cabinet.

Gavin

[kim]

If it's just sand "in a bucket" (not what most people would term a "DSB"), why not just give it a stir once a week and rinse out any detritus ?

Plus without any macroscopic life in there, it doesn't need to be very deep - a couple of inches max I'd have thought. With fine sand, oxygen will penetrate millimitres rather than centimetres. No point having six inches in there.

kim

[Sye Davies]

i wont have the space to try:rolleyes:

[Glenn@home]

If it's just sand "in a bucket" (not what most people would term a "DSB"), why not just give it a stir once a week and rinse out any detritus ?

Plus without any macroscopic life in there, it doesn't need to be very deep - a couple of inches max I'd have thought. With fine sand, oxygen will penetrate millimitres rather than centimetres. No point having six inches in there.

kim

Kim

an interesting point re the depth of sand. Its a common misconception that denitrification needs lots of inches of sand, as i am sure you recall there were some expriments carried out with sans as shallow as 1" - 3" with and without plenums and they all achieved denitrification.

The author of the work, whose name escapes me, didnt claim that this was the ideal setup for a DSb only investigated the issue if denitrification with respect to the depth of sand and the need for aplenum or otherwise.

Personally I wouldnt want a very deep bucket to stir since i know how often i didnt stir the shallow sand bed.

But its is clear that there are many different ideas.

Glenn

[kim]

Glenn,

Without all the life in a "standard" DSB, it's been shown that things are anoxic within a few millimetres of the surface (of fine sand).

Water diffuses only slowly, and the surface living bacteria quickly suck it clean of whatever oxygen it holds before it goes any deeper.

Though a hobbyist is unlikely to be able to show this - without some very fine probes (like sharp sewing needles) measurement is VERY tough. Stick the probe in and you allow oxygenated water to flood into the hole, making the experiment worthless.

To be honest, I'd have thought that a bucket of LR would have more useful denitrifying volume (it presents a larger surface to the water) and be maintenance-free, but Calfo is an advocate and I'm a fan so...

kim

[Johnt]

Do you intend to have fish only with live rock if this is the case Bio balls will filter the water very effectively but not nitrates unfortunately, nitrate won't affect the fish like it does corals and invertebrates.

John.

[Sye Davies]

it will be a reef.

after investigation i will be going for the hugh amount of rock required and adding the dsb as an extra.
the tank will be well stocked so i think its better this way:)