# N2, harmfull or not?



## Ravenswing (11 Feb 2014)

Hi again!

This has been discussed every now and then and -where, according to some discussions or conclusions it is harmfull to have N2 gas in aquarium but on the second place its just good for plants and just one nice and easy way to get rid of N (NO3). I guess this varies and maybe depends more or less on circumstances (planted/non-planted etc ) or...not? Some say it is actually good to have a lot of anaerobic reactions in a tank to get rid of NO3 and that much oxygen is not even needed. Then why it is usually recommended to have as much oxygen into biological filters as ever possible and avoid filter clogging? How about BOD?  Would someone like to clarify this a bit, please, since I dont`understand the whole puzzle yet and all that information seems to be a bit conflicting? BTW, Iv never owned a canister filter so no idea how they work ideally and at optimum level....

Cheers, Maria


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## ceg4048 (11 Feb 2014)

Hi Maria,
			   You should know by now that NO3 haters assume that NO3 is the boogie man, so they will accept any illusion or argument that promises to reduce NO3.

A fundamental symbiotic relationship exists between plants and aerobic bacteria. Plants actually inject Oxygen into the sediment specifically to enhance the growth of aerobic bacteria in the area aound the roots. The aerobic bacterial species in that "Rhizosphere" service the plants by using the oxygen to convert various noxious chemicals into bioavailable nutritional products.

In the case of an unplanted tank. why on earth would you want to have an anaerobic zone? Again, the NO3 haters are so afraid of NO3 that they are willing to sacrifice Oxygen availability just to be rid of NO3. Anaerobic bacteria produce many products noxious to fish, such as Hydrogen Sulfide.

The Matrix isn't real Maria....

Cheers,


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## dw1305 (11 Feb 2014)

Hi all,





Ravenswing said:


> to have N2 gas in aquarium but on the second place its just good for plants and just one nice and easy way to get rid of N (NO3).


 You can out gas nitrogen via anaerobic denitrification, but the N2 molecule is totally inert, the triple bond between the 2 N atoms require a huge amount of energy to split into the molecule (into very reactive N atoms), so N2 doesn't have any function in plant growth.  





Ravenswing said:


> Some say it is actually good to have a lot of anaerobic reactions in a tank to get rid of NO3 and that much oxygen is not even needed.


 There will nearly always be some anaerobic zones in the substrate where de-nitrification may occur, but for filters this is based upon a misconception.

There is a theoretical "sweet spot" where you have both aerobic and anaerobic reactions in the filter, but the problem is maintaining that balance, if the filter becomes de-oxygenated (and we need to be right on the cusp of de-oxygenation to have both aerobic and anaerobic zones within the filter media) the NH3 passes straight through the filter and can rapidly build up to toxic levels.

Rather than balancing on the razor edge between aerobic/anaerobic you can just supply enough oxygen to keep all the filter media oxygenated.

It is a "_win win"_ situation, if you have a huge increase in bioload (dead fish perhaps) rather than your filter bacteria being over-whelmed by the extra ammonia starting off a positive feed-back loop of more NH3 > more deaths > less oxygen, you just get an increase in the amount of NO3 produced by the filter.

We know high levels of NO3 aren't toxic on their own (due to Tom and Clive's work with the NO3 from KNO3 addition in EI), and that the increase in NO3 will start a negative feedback loop where more NO3 will stimulate more plant growth, which will lead to more plant growth, which will take up more NO3, potentially _ad infinitum_.





Ravenswing said:


> Then why it is usually recommended to have as much oxygen into biological filters as ever possible and avoid filter clogging? How about BOD?


Personally I use a "low BOD" philosophy, this allows you to maintain high water quality, although it may be sub-optimal for plant growth.

There is a bit more of an explanation here: <View topic - Wood for tanks?> and <http://www.ukaps.org/forum/threads/alfagrog-for-reducing-nitrates.19636/>.

cheers Darrel


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## Ravenswing (13 Feb 2014)

Argggghhhhh... I wrote a long answer and them my computer fell!!! Short version, lucky you:



ceg4048 said:


> The Matrix isn't real Maria....


 
Yes, as I have written earlier, I personally take this quite easy but I really like to solve conflicts and dilemmas that I find or dont understand. I think this makes this hobby worth of it (besides beautiful tanks), and not every issue I try to figure out is mine. Just like to know and learn! You and Darren are absolutely my favs explaining things so clearly. Thank for your input, you always give me alot to think about!

So does Darren. Thank you sir!



dw1305 said:


> Rather than balancing on the razor edge between aerobic/anaerobic you can just supply enough oxygen to keep all the filter media oxygenated.


 
Thats what I have thought allways too. Its a risky business to establish anaerobic areas, dumps, on purpose just in order to get rid of NO3 but thats what some do as I have heard. Probably more harm than good.


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## Ravenswing (13 Feb 2014)

Oh, I forgot this Deep Sand Beds. What do you like? Not that I would try, Its just something Iv never seen (?). Is it similar to Walstad style soil substrate with similar idea?


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## dw1305 (13 Feb 2014)

Hi all,





Ravenswing said:


> Thats what I have thought allways too. Its a risky business to establish anaerobic areas, dumps, on purpose just in order to get rid of NO3 but thats what some do as I have heard. Probably more harm than good.


 Yes I'm fairly confident that entirely aerobic filter media is the way forward. We've done a bit of work on the re-mediation of "landfill leachate"  (and it actually looks like we may be setting the lab back up for this), which you can think of as "uber-polluted" tank water. The out come of this is that highly oxygenated systems using microbial & plant filtration are about an order of magnitude better than any other option, and have the capacity to deal with huge bioloads. 





Ravenswing said:


> Oh, I forgot this Deep Sand Beds. What do you like? Not that I would try, Its just something Iv never seen (?). Is it similar to Walstad style soil substrate with similar idea?


 Maria I enjoyed the article, and the description is pretty much how I run my "tank in the kitchen". This was it a few years ago (2011), but other than being more over-grown it hasn't changed much. It was set up in 2008, the substrate was about 90% sand with a bit of gravel, but it has mainly housed _Apistogramma_, and over time the gravel has migrated to the top.




It has _Asellus_, MTS, _Lumbriculus_ etc in the substrate. I don't vacuum the substrate, and areas of restricted flow have a mulm layer, in some cases 1-2 cm thick.

Most substrates will have both aerobic and anaerobic zones, and that is to our advantage. Have a look a these <Undergravel filters | UK Aquatic Plant Society>,  <De-nitrification | The Skeptical Aquarist> & <Winogradsky column | The Skeptical Aquarist>.

cheers Darrel


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## Ravenswing (13 Feb 2014)

Thats cool. The idea of the substrate of your tank I mean. Seems to work well! One day Id like to try some soil based substrate ala Walstad but so far been to lazy to do that. Sand is so easy thou in some of my tanks I use JBL Manado. Thanks for the links, have to read them with plenty of time!


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