# natural nitrate reduction (nnr) in freshwater



## nitrofish (Jan 14, 2003)

I was reading about nnr in saltwater tanks,and one tecnique was to use a deep sand bed. now I was wondering if that would work on freshwater as well?


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## DonH (Jan 25, 2003)

Not a good idea... A deep gravel bed will promote anaerobic conditions and can potentially release hydrogen sulfide if not maintained.


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## Peacock (Feb 23, 2004)

bingo...

if you want NNR set up a 100 + gallon refuge, hook up a medal holide and jamm it with plants.. floating plants would be best.. also get a few air stones to rotate the plants around exposing all plants to the medal holide.


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## vtecbro007 (Feb 11, 2004)

im soo lost


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## Guest (Mar 1, 2004)

The nitrifying bacteria that can convert nitrate (NO3) to Nitrogen gas (N2) are inhibiting by oxygen. I would guess that a deep mud/sand anaerobic environment would be difficult thing to replicate safely in a freshwater tank.


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## nitrofish (Jan 14, 2003)

I wasn't going to do it, I was just wondering if it would work.

plus 6" of sand looks so un natural


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## ttldnial (May 14, 2003)

Peacock said:


> if you want NNR set up a 100 + gallon refuge, hook up a medal holide and jamm it with plants.. floating plants would be best.. also get a few air stones to rotate the plants around exposing all plants to the medal holide.
> 
> AND- why would floating plants be better?


 This I like...

If one had a 100+ gallon refuge full of plants and a halide or sodium would the 
nnr be significant?

say you have 2 100 gallon tanks.1 display tank with fish, 2 the fuge full of plants..


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## DonD (Mar 11, 2004)

I would say it depends on how you set it up. As just a deep gravel bed, I agree with DonH. Bad idea.
However, setting up a plenum in FW could work. Its debatable, but I think it is a sound theory, at least on paper. LOL
A plant filter would indeed do the trick marvelously. You would just have to pick the proper plants. Quick growers that suck up nutrients like Java moss, Vals, hornwort...things like that.
A denitrator would work also in FW though they were originally designed for SW tanks.
DonH, It took me a bit, but I made it over here.


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## Peacock (Feb 23, 2004)

DonD said:


> I would say it depends on how you set it up. As just a deep gravel bed, I agree with DonH. Bad idea.
> However, setting up a plenum in FW could work. Its debatable, but I think it is a sound theory, at least on paper. LOL
> A plant filter would indeed do the trick marvelously. You would just have to pick the proper plants. Quick growers that suck up nutrients like Java moss, Vals, hornwort...things like that.
> A denitrator would work also in FW though they were originally designed for SW tanks.
> DonH, It took me a bit, but I made it over here.


 Donald tubesteakheadson ??? LOL remember that one? damn Pfish chat filter. lol

Welcome Donald D! good to see you over here backing us up!


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## DonH (Jan 25, 2003)

DonD said:


> DonH, It took me a bit, but I made it over here.


Hey Don! Glad to see you here... For those who don't know Donald Dickson, he has a wealth of info about water chemistry and cichlids (also wrote an excellent article on Hole in the Head Disease). Welcome to P-Fury!

The two Dons! Just like the old days...


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## Grosse Gurke (Jan 3, 2003)

DonH said:


> The two Dons! Just like the old days...


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## Xenon (Nov 15, 2002)

DonH said:


> The two Dons! Just like the old days...


 I second that notion.


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## nitrofish (Jan 14, 2003)

sweet


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## DonD (Mar 11, 2004)

Hey, I figure I should post where ever you can point out where I screw up Don. Keeps me on my toes. LOL


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## illnino (Mar 6, 2004)

vtecbro007 said:


> im soo lost


 same here


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## nitrofish (Jan 14, 2003)

illnino said:


> vtecbro007 said:
> 
> 
> > im soo lost
> ...


heres some reading for you

To help understand the key features of natural nitrate reduction and the role of sand filters we must focus on the open systems in nature to compare our more finite marine application. Our goal is to maintain a nutrient poor environment as per the guide-line for coral reef eco-systems. In the case of our reef aquaria, we first build an environment trying to achieve eco-system's basic requirements. To do so successfully the crucial elements must be provided in the ratios necessary for balance .

The fundamental driving forces are chemical and radiant energy. These elements are interrelated complexly and mediated biotically and/or abiotically. With the topic of NNR and living sand filtration the process of denitrification is where we started. The process is mediated by bacteria (microbes). The deposition of organic material on the surface layer of marine sediments supports an elevated microbial metabolism and limits the penetration of O2 into substrata (Sand). It produces an ideal environment for microbial NO3- reduction. It is created in an environment where NO3 can be in ample supply to substitute for O2 in the process of organic matter degradation.

In sediments, this would involve only a very thin layer that interfaces with the bulk water. In systems using porous rocks for filtration i.e. Berlin Method, this would include the rock to water surfacial interface with slight modification. In natural marine sediments the oxic/anoxic (high oxygen/minimal oxygen) interface varies from a few millimeters to several centimeters. In other words less than half an inch. So then, what is a segregated sand bed, with a plenum space underneath going to do for the axiom of nitrate reduction (denitrification). Plenty ! !

The presence of the surfacial interface, the area at the sand's surface where oxic conditions are changed to anoxic conditions by microbial metabolism of organic matter, does not change much in the living sand filter. In fact it seems extended or enhanced. What goes on below is where the difference becomes apparent after measuring variables like nitrate, oxygen, pH, H2S, and alkalinity.

Normally in marine sediments, the area below the oxic/anoxic microzone is essentially anaerobic, with decreasing O2, pH, and redox. The diffusion of elements to and from the obligate anaerobes is slow and at a reduced capacity compared to the surface microzones. Any observed increased activity is most often the result of plant and animal infauna increasing the net volume of surfaces and availability of oxygen. In the aquarium's sand bed system the elements traverse horizontally and vertically throughout the sediment substrate and plenum. Oxygen can be measured at anoxic levels at varying times throughout the sand bed and plenum. Or oxygen can be present at one level even if the sand layer above is temporarily anaerobic, and partitioned from the aquarium water as a source of dissolved oxygen. 
Nitrate concentrations have been seen to have definite movement toward the plenum and often accumulate there in higher concentration than the aquarium's water. Nitrate production from an organic load can be seen to diffuse gradually through the sand layers to the plenum. Associated with this transition is a gradual reduction of oxygen levels, and pH. Interestingly, total alkalinity is observed to increase slightly with proportional pH decrease.

To surmise the observations it would be possible to conclude one of the biggest contributions of this sand bed (NNR) system is to use facultative bacteria as opposed to obligate bacteria. Obligate anaerobes are found mostly in the natural marine sediment environments below the anoxic microzone. They only metabolize and grow in anaerobic conditions.

However, the facultative microbial populations can metabolize and grow with oxygen or reduced oxygen. This ability really enhances nitrate reduction capability. To implement a facultative design that is at least three inches deep by the length and width of the aquarium provides tremendous potential to filtration in this regard. It aids destructive denitrification and shunts assimilative denitrification. In the first case nitrate is broken down into its elements.

In the second case nitrate is rebuilt into ammonia for use by nitrogen fixers as fuel. We most often complain about the growth of nitrogen fixers like nuisance algae. They are very good at using nitrate that has been reassembled into ammonia. Unfortunately. The processes gets tremendously more complex as more nutrient pathways are investigated for inter-relationships. Perhaps this is a good place to stop and get into the design and building of a typical (generic) system next time.


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