Deep Sand Beds - do they work?

[Siput]

Bought my 3 ft tank today. Talking to the guy selling the tank, I mentioned that I was thinking of using a DSB for denitrification. He surprised me by saying that in his opinion, DSBs do not work as well in the tropics as in the temperate countries. Reasoning as folllows:

In temperate countries, the water/rrom temperature is usually lower, and as a result, people tend to use heaters both in the tank as well as in the cabinet or under the gravel. The temperature differences between the sand bed and the water resulting from these heating practices actually encourage the flow of water through the DSB to some extent (hot water goes up, cooler water sinks), leading to a constant proces of renewal.

In the tropics however, the water and DSB temperature remains fairly constant, so water exchange between the DSB and rest of aquarium is minimised. Thus this largely negates the denitrification process and as the end products is also kept within the DSB, any disturbance of the DSB over a long period f time cold prove fatal to the rest of the tank. *Just a thought* - is this why some pple "supplement" with UGF? To increase water flow?

Sorry for the long thread, but anyone have any comments on the above? I still favour the idea of a DSB myself, but as a newbie would apprec any advice from the more experienced members...many thanks!

[FuEl]

It's best that waterflow thru a DSB is kept to the minimum as possible. This is the reason why for remote DSB in sumps, water flows OVER the DSB...not filtering thru a DSB. If water movement thru a DSB is rapid, oxygen concentration in the DSB would be higher, leading to little or even no anoxic zone for anaerobic bacteria to grow, impeding denitrification.

If water movement thru a DSB is slow, it would be best, as less oxygen enters the DSB, enabling an anoxic zone to form for anaerobic bacteria to form.

Using a U.G would render the DSB useless as fresh oxygen will oxygenate the DSB, enabling only aerobic bacteria to form, causing nitrate buildup over time.

Actually...IMO..a DSB works better in tropical climates due to lower levels of dissolved oxygen levels in the water and due to higher metabolic rates of organisms. Less dissolved oxygen would thus enter a DSB, making it possible for a large anoxic zone to be formed.

Anaerobic bacteria use sulphur as they break down nitrates into nitrogen gas. The biproduct of this process would be hydrogen sulphide which could build up in the DSB. If levels of hydrogen sulphide is high, disturbance of the DSB could release hydrogen sulphide into the water, causing a rapid drop in pH, and causing inhabitants to die due to pH shock.

Hope I am speaking sense...

[Achilles Tang]

Funny theory.

Reefs are found in the tropics. Where the air is warm and the water is warm too.

Most of us have chillers that maintain our water temp around 25 to 26.

How does that affect DSBs in the tropical zone???

The logic is flawed.

[Siput]

In this case therefore can I say that both good and bad come out of the DSB? Ie, if I understand you properly, yes, the DSB reduces nitrates into nitrogen gas, so it is good, but also causes hydroegn sulphide, which could be lethal to the tank if released?

If this is the case, how do I get rid of the nitrogen sulphide whilst getting the benefits of the DSB?

Many tks in advance...

[Siput]

Funny theory.

Reefs are found in the tropics. Where the air is warm and the water is warm too.

Most of us have chillers that maintain our water temp around 25 to 26.

How does that affect DSBs in the tropical zone???

The logic is flawed.

I think he mentioned that even with chiller, it would be still uniform temperature thorughout over time (as opposed to warm sand/cold water or vice-versa).

Anyway, also served to confuse me....I thought the DSB method was a very good way to go after going through quite a few articles...

[FuEl]

In this case therefore can I say that both good and bad come out of the DSB? Ie, if I understand you properly, yes, the DSB reduces nitrates into nitrogen gas, so it is good, but also causes hydroegn sulphide, which could be lethal to the tank if released?

If this is the case, how do I get rid of the nitrogen sulphide whilst getting the benefits of the DSB?

Many tks in advance...

If I'm not wrong the hydrogen sulphide would seep out very very slowly by simple theory of diffusion. But at such a rate would do minimal impact to your pH....

If you were to dig up your DSB for some reason or another then all the hydrogen sulphide will be released at once, causing a major pH disaster.

Hope my guess is correct.

[Siput]

Thanks for the help. Guess will try the DSB method in combination with lots of LR.

[FuEl]

Thanks for the help. Guess will try the DSB method in combination with lots of LR.

No prob..if I were to change my tank I would do something like this.

Back 3/4 of the tank...2/3 of the space use for DSB..1/3 use for plenum

front 1/4 of the tank...use plenum...then just below the top layer of sand add one U.G plate trimmed to size as microfauna nursery before gently covering with a layer of sand.

[Siput]

sounds complex....but interesting idea...must read up more on how do do this...many thanks!

[alanseah]

for me I'm too lazy to go throught so much step..

I will rise 1" for plenum and then cover it with 4-5" of sand

so as to make use of the whole surface of the tank to max the plenum.

[RockyBoy]

DSB at my refugium really helps. Nitrates level drops significantly than without DSB.

[trevally]

Hi all,

I have heard from other reefers saying that DSB are only good for 2-3 yrs, after that u have to somehow maintance it else it will crash ...in other words, DSB are like time bomb, how true is it?? i also dunno...can anyone verify this??

[CooL_anakin]

I think in my opinion many people are unaware that the most important espect in a DSB are the critters inside it.

It relies on them to keep the sand bed from clumping. Movement of these infauna pumps water into the lower levels preventing them from becoming completely anaerobic, and facilitating the biological filter.

Temperature has little to do with water exchange. Particles will still diffuse with the concentration gradient[from a region of higher concentration to a region of lower concentration] no matter the temperature.

It basically has 2 main factors, Sand Bed n Infauna.

[CooL_anakin]

Hi all,

I have heard from other reefers saying that DSB are only good for 2-3 yrs, after that u have to somehow maintance it else it will crash ...in other words, DSB are like time bomb, how true is it?? i also dunno...can anyone verify this??

It wouldn't be a time bomb if you maintain the infauna inside a DSB.

The problem with DSBs in SG is that we don't have "Refugium Kits" available to recharge the infauna every year or so. Time bombs happens when the sand bed clumps and not enough fauna is present to process the detritus n "pump water" into the lower levels. So you have to make sure there's a diversity of animals living in your sand bed and there shouldn't be a problem.

http://www.rshimek.com/reef/sediment.htm This is a good reference for DSBs.

[alanseah]

talking about that.. it did mention something like this..

"There is absolutely no need for any subsurface sand structure such as a "plenum" or shelf. In fact such structures will reduce the sediment volume that is available for the bacteria."

[alanseah]

also for those worry about Hydrogen sulfide

"Hydrogen sulfide is an amazingly toxic gas, but that toxicity is exceeded by its pungent rotten-egg odor. The gas will have an exceptionally strong odor, and will seem overwhelming at levels well BELOW toxic amounts. If you can smell this stuff without it literally taking your breath away, it won't be at a harmful concentration. There is no real evidence to indicate that it may reach toxic levels in a deep sand bed."

[Octopus Bay]

can this picture tell the story??

[Siput]

It wouldn't be a time bomb if you maintain the infauna inside a DSB.

The problem with DSBs in SG is that we don't have "Refugium Kits" available to recharge the infauna every year or so. Time bombs happens when the sand bed clumps and not enough fauna is present to process the detritus n "pump water" into the lower levels. So you have to make sure there's a diversity of animals living in your sand bed and there shouldn't be a problem.

http://www.rshimek.com/reef/sediment.htm This is a good reference for DSBs.

Bro cool anakin, thanks for the article. very informative!

[AlfaRomeo]

After reading lots of info in reefcentral about DSB, there is a big ? on how long a DSB will last without crashing. Some ppl swear by it while others are willing to die rather than using DSB again. Most of the DSB opponents main gripe is that the DSB is like a sponge with a limited absorbing ability and porcessing effectiveness. If you tend to feed your fishes lots and tend to overfeed, then the DSB cannot process the extra junk fast enuff and will tend to accumulate in the deeper layers of the DSB and after some time, the DSB will be a source of pollutants to the water column instead of helping to process nitrate. This is my simple understanding of why a DSB work for some ppl and not others. Pls enlighten me if i got some of the concepts wrong. Cheers!

[CooL_anakin]

No problem. Nice Refugium? Clean and neat. Mine is like a slump literally.

[alanseah]

After reading lots of info in reefcentral about DSB, there is a big ? on how long a DSB will last without crashing. Some ppl swear by it while others are willing to die rather than using DSB again. Most of the DSB opponents main gripe is that the DSB is like a sponge with a limited absorbing ability and porcessing effectiveness. If you tend to feed your fishes lots and tend to overfeed, then the DSB cannot process the extra junk fast enuff and will tend to accumulate in the deeper layers of the DSB and after some time, the DSB will be a source of pollutants to the water column instead of helping to process nitrate. This is my simple understanding of why a DSB work for some ppl and not others. Pls enlighten me if i got some of the concepts wrong. Cheers!

that is why those cleaning crew are needed e.g. sand worm shrimp, etcs..

[AlfaRomeo]

Alanseah, but dunt the DSB has a limited processing capacity and if you feed and overload the DSB will more junk than it can process, then the DSB will crash after some time due to the accumulation of the dirt in the lower layers of the bed.

[CooL_anakin]

After reading lots of info in reefcentral about DSB, there is a big ? on how long a DSB will last without crashing. Some ppl swear by it while others are willing to die rather than using DSB again. Most of the DSB opponents main gripe is that the DSB is like a sponge with a limited absorbing ability and porcessing effectiveness. If you tend to feed your fishes lots and tend to overfeed, then the DSB cannot process the extra junk fast enuff and will tend to accumulate in the deeper layers of the DSB and after some time, the DSB will be a source of pollutants to the water column instead of helping to process nitrate. This is my simple understanding of why a DSB work for some ppl and not others. Pls enlighten me if i got some of the concepts wrong. Cheers!

Overfeeding and stuff is when the scavengers come in. [Nassarius, bristleworms etc.] They'll clear up left over food before they're broken down by bacteria. Crashing IMO wouldn't occur if you constantly replenish your detrivores. Just like i said earlier, The critters are important in a DSB, its like cleaners or workers in a cleaning agency(DSB).

Perhaps for those who failed using the DSB they didn't have enough fauna in their tank to help process detritus n leftovers, leaving most of the job for the DSB which can not handle the over excessive load.

Thus becoming a sponge.

Its like a company without workers[fauna] and all the contracts[waste material] have to be on hold. And the work load gets more n more[just like nitrates].

That's my understanding too..

[moomoofish]

Hello...

Must the sand for DSB be "0 Grade"???????????

MMF

[alanseah]

grade 0 or 1 will be gd