# Safe Freshwater Deep Sand Bed



## Matt1986 (May 15, 2009)

Hi there,

I'm interested in trying to build a denitrator system for my tank - partly because of the challenge/curiosity, partly due to travelling a lot and leaving tank maintenance in the hands of my brother.

I've read lots of sceptical accounts of using DSB's in freshwater due to the potentially deadly gaseous toxins produced by anaerobic bacteria. However, if you made a DSB in an open sump box, wouldn't these gasses be isolated from the main tank?

I'm thinking of designing a combined DSB/Refugium to supplement my existing sump and hopefully remove some Nitrates - can anyone suggest why this might not work? Are the toxins released by anaerobic bacteria water-soluable or will they simply pass into the air?

Thanks, looking forward to hearing some input,
Matt


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## Mcdaphnia (Dec 16, 2003)

This dsb does not sound like a device you'd want to leave in the hands of a disinterested? brother. If you can find an open cell ceramic sponge about 9" by 9" by 4", it would be much more dependable and failsafe than the deep sand bed. From what I've read it's not the hydrogen sulphide producing anaerobes (sewer bacteria) that convert nitrate to nitrogen gas, but other bacteria that do their work at very low oxygen levels. I am using a few of these sponges and have had them for years. Whether they are set in a sump or directly in the tank in an area of gentle water flow, they work very well. It does take a few months at the beginning for them to be colonized by the bacteria. Tanks up to 125 will always have 0 nitrates with one or more of these blocks in the system.


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## Matt1986 (May 15, 2009)

He's not so much disinterested, just not really up to scratch on the scientific side of fish keeping - although I can't imagine a DSB requiring much maintenance?

I was under the impression that anaerobic bacteria ARE bacteria that exist in low oxygen environments such as a DSB. I thought the whole principle was that oxygen is consumed by denitrifying bacteria and organisms living in the bed (I'm thinking of trying blackworms), so that the deeper recess of the bed is deprived of oxygen, thus allowing for anaerobic bacteria to colonise.

I am interested in those sponges you mentioned though - are they something simmilar to this? (Just trying to get an idea).









I'm still tempted to go with the DSB - the only downside I can forsee is that unlike saltwater tanks which have an abundance of micro-organisms to populate the sand bed, I'd be pressed for freshwater equivalents; just worms and snails really.

Keep the feedback coming,
Matt


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## ManiacalMbunas (Oct 13, 2009)

You don't have to worry about any organisms to consume the o2. The anaerobic environment will naturally occur inside the DSB (or the ceramic sponge/matrix/etc). I personally use bags of Matrix in my sump, although any of these ideas would work. Instead of adding any more equipment, I'd lean towards the ceramic sponges or matrix into your existing sump - same results with less hassle than a DSB (and no chance what so ever of disturbing the anaerobic bacteria). Whichever direction you chose, remember that it will take 2 - 3 months before you see any results.


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## Mcdaphnia (Dec 16, 2003)

If you go with the sand, marble crayfish, Maylasian burrowing snails, and horseface loaches would be alternatives for saltwater dsb critters.

That looks like the ceramic sponge. Can't read the Chinese.  If it is thin sheets, just stack it to four or five inches thick. Hope it's not contaminated like the Chinese pet food and Chinese drywall was.

I agree 90% with Maniacal, :thumb: but you probably could already tell that. The only thing I might question is if anaerobe is the precise term we should use. I think we should be calling them facultative bacteria. Anaerobes can pop up almost instantly and we are culturing something in DSB or a porous matrix that can take months to properly establish itself. Some sources leave you thinking that it is the aerobic bacteria that convert ammonia into nitrite in well oxygenated conditions that will denitrate under low oxygen conditions. But other sources I'd trust more call them a third type of bacteria, facultative.


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## padlock 08 (Jul 31, 2008)

why do you want to do a deep sand bed in a freshwater set-up in the first place when there are easier alternatives?

sorry if i seem patronising but surely it would just be far easier to use a denitrator feeding back in to your sump, then you would have 0 nitrates and, to my knowledge, zero maintenance. And as it's feeding to your sump you don't have to worry about poisoned fish.

here's a link from this same forum on how to make a denitrator
http://www.cichlid-forum.com/phpBB/viewtopic.php?t=184805

-Paul


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## Matt1986 (May 15, 2009)

I just figured that setting up a DSB would be less hassle, and adding an additional sump to my system would have the benefit of adding gallonage. But those denitrators do look quite easily buildable, and if they work then maybe that's the way forward.


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## padlock 08 (Jul 31, 2008)

i think it would be more cost effective and efficient to build this denitrator as you already have a sump don't you? a refugium can always be added for extra gallonage if you want another or drain the denitrator into the second sump then back to the aquarium, this should keep your nitrates down plenty


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## TKC747 (Dec 5, 2008)

If you have a cansiter filter, Seachem Matrix supposedly will host anaerobic bacteria that will complete the nitrogen cycle. Aerobic bacteria on the surface. I bought some but have no experience as yet...


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## Mcdaphnia (Dec 16, 2003)

TKC747 said:


> If you have a cansiter filter, Seachem Matrix supposedly will host anaerobic bacteria that will complete the nitrogen cycle. Aerobic bacteria on the surface. I bought some but have no experience as yet...


 I have some matrix too that I haven't used yet. but I did read the label and the manufacturer's claims including this one. http://www.seachem.com/support/SpecificSurface.pdf

And I found nothing there suggesting that anaerobic bacteria would be in the medium and certainly no suggestion that anaerobic bacteria would denitrate. Anaerobes play with sulphur, not nitrates, and produce hydrogen sulphide gas, not nitrogen gas.


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## Fishbulb2 (Sep 23, 2008)

Mcdaphnia said:


> Anaerobes play with sulphur, not nitrates, and produce hydrogen sulphide gas, not nitrogen gas.


I don't think this is true. Anaerobes certainly play a major role in anaerobic denitrification. Sulfate reduction to hydrogen sulfide gas typically takes place in anoxic conditions with even lower oxygen levels.

http://en.wikipedia.org/wiki/Denitrification This describes a bit of bacterial denitrification but you can find more info anywhere on the web on it.


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## Mcdaphnia (Dec 16, 2003)

Fishbulb2 said:


> Mcdaphnia said:
> 
> 
> > Anaerobes play with sulphur, not nitrates, and produce hydrogen sulphide gas, not nitrogen gas.
> ...


You should read what you link to as "support" for your idea since it references "aerobic denitrification" and does not ascribe any contribution by anaerobic bacteria, except facultative anaerobes which can switch to aerobic or anaerobic . There are plenty of links you could have found that shorthand the low oxygen levels at which denitrification takes place as anaerobic. Anaerobes can play a major role in predigestion of nitrogenous wastes, but that statistic is from treating the liquid wastes from pig urine and stool. I am pretty sure we don't want to let our tank water get to the point it has to be predigested before it can be denitrified. To quote a paragraph from Saturnnet:

Clostridium perfringens and Clostridium botulinum are generally considered to be anerobic bacteria.

Aerobic bacteria require oxygen for growth. Listeria (reduced oxygen levels), E. coli, and Campylobacter are generally considered to be aerobic bacteria.

Facultative bacteria are those that can grow with or without oxygen. Unfortunately, most of the bacteria implicated in foodborne illness are facultative in varying degrees. Salmonella, Shigella, Staphylococcus aureus, and Bacillus cereus are generally considered to be facultative bacteria.


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## PGWald (Feb 2, 2008)

McDaphnia or anyone who might know, is there any data that demonstrates quantified denitrification with the use of the open cell ceramic foam you mentioned or is it all anecdotal evidence? Does the concept only work with open cell ceramic foam or does it also work with other porous foams such as reticulated vinyl foams?

It'd be great to be able to reduce Nitrates down to N2 gas that could be eliminated from the aquarium environment. The use of open cell foams is a lot simpler than constructing a denitrator unit in my view. But, I'd be much more comfortable if there were some data that quantified the results. I did an initial search on the internet for documentation and found none so far. I did find references to several medical papers which talk about the types of facultative bacteria which affect humans. What sources did you read that document that open cell ceramic foam can serve as a medium for facultative bacteria that then reduce nitrates to N2 gas? Thanks!

Jim


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## PGWald (Feb 2, 2008)

McDaphnia or anyone who might know, is there any data that demonstrates quantified denitrification with the use of the open cell ceramic foam you mentioned or is it all anecdotal evidence? Does the concept only work with open cell ceramic foam or does it also work with other porous foams such as reticulated vinyl foams?

It'd be great to be able to reduce Nitrates down to N2 gas that could be eliminated from the aquarium environment. The use of open cell foams is a lot simpler than constructing a denitrator unit in my view. But, I'd be much more comfortable if there were some data that quantified the results. I did an initial search on the internet for documentation and found none so far. I did find references to several medical papers which talk about the types of facultative bacteria which affect humans. What sources did you read that document that open cell ceramic foam can serve as a medium for facultative bacteria that then reduce nitrates to N2 gas? Thanks!

Jim


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## PGWald (Feb 2, 2008)

McDaphnia or anyone who might know, is there any data that demonstrates quantified denitrification with the use of the open cell ceramic foam you mentioned or is it all anecdotal evidence? Does the concept only work with open cell ceramic foam or does it also work with other porous foams such as reticulated vinyl foams?

It'd be great to be able to reduce Nitrates down to N2 gas that could be eliminated from the aquarium environment. The use of open cell foams is a lot simpler than constructing a denitrator unit in my view. But, I'd be much more comfortable if there were some data that quantified the results. I did an initial search on the internet for documentation and found none so far. I did find references to several medical papers which talk about the types of facultative bacteria which affect humans. What sources did you read that document that open cell ceramic foam can serve as a medium for facultative bacteria that then reduce nitrates to N2 gas? I'm intrigued. :dancing: Thanks!

Jim


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## PGWald (Feb 2, 2008)

McDaphnia or anyone who might know, is there any data that demonstrates quantified denitrification with the use of the open cell ceramic foam you mentioned or is it all anecdotal evidence? Does the concept only work with open cell ceramic foam or does it also work with other porous foams such as reticulated vinyl foams?

It'd be great to be able to reduce Nitrates down to N2 gas that could be eliminated from the aquarium environment. The use of open cell foams is a lot simpler than constructing a denitrator unit in my view. But, I'd be much more comfortable if there were some data that quantified the results. I did an initial search on the internet for documentation and found none so far. I did find references to several medical papers which talk about the types of facultative bacteria which affect humans. What sources did you read that document that open cell ceramic foam can serve as a medium for facultative bacteria that then reduce nitrates to N2 gas? I'm intrigued. :dancing: Thanks!

Jim


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## FSM (Nov 11, 2009)

have you thought about making an algae scrubber? Basically just a sheet of material placed in the sump with water pumped over it + lots of light shined on it to encourage algae growth.


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## Matt1986 (May 15, 2009)

FSM,

I have looked into them and found a good build for one, but basically I'm still tempted by the low maintainance of a combined DSB/Planted Refugium. Like PGWald I'm also very interested in the open ceramic foam option, but I want to know a bit more about how effective it is before I give it a shot.

All in all I see very few downsides to just getting a plastic sump, filling the bottom half with sand and the top half with duckweed, placing it under timed lights and circulating it with a small pump from my main sump. Should that not work, in theory at least?

Matt


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## Mcdaphnia (Dec 16, 2003)

When the ceramic foam first came out, I set up a 75 with it and did not water changes in that tank for over two years. I loaded the tank up with juvenile African cichlids and grew them up feeding heavily. There was always zero nitrates in the tank. Most of the time there was also a FBSF on the tank too and the two very different filtration concepts worked well together.


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## Matt1986 (May 15, 2009)

Mcdaphnia,

In what way are they best added to a sump? Should I have them standing vertically accross the width of the sump so that water is forced through them, or would it be sufficient just to lay them flat along the bottom of the sump?

I think I'm going to give them a whirl based on your experiences.

Cheers,
Matt


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## Mcdaphnia (Dec 16, 2003)

The 4" thick slab should be flat on the bottom, but under water beneath the water flow. Here is a link to an animation, but the denitrator slab is out of the picture below the action.
http://www.foryourfish.com/FilWD_BioRockerAnim.gif

There used to be a lot more pics of these online, but they aren't made commercially anymore. Now they're a DIY project. If you can't get the ceramic open pore sponge, you can make the wet/dry and the denitrator block out of the medium or fine Poret foam.


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## Matt1986 (May 15, 2009)

I've found some cheap bio ceramic sponges available here in Australia so I should be all set, I'll report back in a few months time to evaluate their effectiveness :thumb:


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## PGWald (Feb 2, 2008)

McDaphnia,

Can you speculate whether the concept also would work with open cell vinyl foam (reticulated foam) slabs of similar thickness to the ceramic foam? Presumably, the way the ceramic foam provides denitrification is that there are many interior pores that do not see oxygenated water flow so the facultative bacteria living in those pores adapt to a low-oxygen or anoxic condition and digest the nitrates as an oxygen source and release N2 gas as a byproduct of the process. If that's generally what is happening in the ceramic foam, why wouldn't it occur in other types of similarly configured foam types? Any thoughts on this?

Matt1986,

In case you were still interested in researching sand filtration after trying the ceramic foam concept, I seem to remember there was a author named Bob Goemans, I think, who wrote a series of articles for _Freshwater and Marine Aquarium_ magazine some years back about sand filter systems for marine aquariums. After a while he was being asked by readers to comment on the use of such filtering sand in freshwater aquariums. This had to do with the use of plenums under the sand substrate where near anoxic conditions were supposed to be created that would, in theory at least, reduce the nitrates to gaseous nitrogen which would dissipate out of the water and kept dissolved nitrates at something approximating zero if the dept of the sand and the plenum were sized properly. Sorry, but I can't recall which issues nor even which years these articles ran but you may be able to find them in a search of FAMA article titles online.

Jim


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## Mcdaphnia (Dec 16, 2003)

Those Goemans live sand articles were updated and compiled into a book about ten years ago. I've seen copies of it recently for $3 at Amazon.

Yes the Poret foam and plastic pond mats such as Matala should all denitrate when the flow is "just right" and the bioload is not insane.


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## Matt1986 (May 15, 2009)

Jim,

Thanks for the tip, I'm still very curious about sandbeds and managed to stumble across a couple of articles by Bob Goemans and Sam Gamble taken directly from FAMA at http://www.saltcorner.com/sections/guest/goemansandgamble/sandbedspart1.htm.

Cheers,
Matt


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## neptunegrandma (Nov 12, 2016)

What about using the bricks they use in kilns. They are very light weight so they much be porous.


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## Mcdaphnia (Dec 16, 2003)

Something like this might be an option from the kiln supply industry. https://www.smokehomegarden.com/store/5 ... 5_for.html Just because a kiln brick is light weight does not mean it has open cell construction. Closed cell does not seem like a safe choice when being heated and cooled, but just how open the cell structure is would be a question. You would have to find out if these products are inert in water.


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