Aquarium Chemistry: The Nitrogen Cycle: New Developments and New Prospects

Discussion in 'Water Parameters and Additives' started by dallasg, 20 Apr 2011.

  1. dallasg

    dallasg Moderator MASA Contributor

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  3. viper357

    viper357 Admin MASA Contributor

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    Yup, I knew that. :1eek:
     
  4. crispin

    crispin

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    hell i didnt:1confused:
     
  5. Reef Maniac

    Reef Maniac MASA Contributor

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    Excellent article :thumbup:

    What's most significant IMHO is the "Nitrogen cycle as revised and integrated" diagram (Figure 7), where he shows that nitrate (NO3) can change back into nitrite (NO2) and ammonia (NH4) in the Anoxic zone deep in the sand bed (below the Suboxic zone, which is what we want in our DLSB's).

    This suggests that one should NOT MAKE THE SAND BED TOO DEEP :eek:

    Hennie
     
  6. ziyaadb

    ziyaadb

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    Great point hennie but with tech today there are very few reefers that are still utilizing a DSB both local and international. I see the trend moving towards N P Pellets, probiotics, carbon dosing and refugiums. anyone else notice this?
     
  7. SchyffS

    SchyffS Reef Aquarist

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    The article has depth....in the end it boils down to enzyme actvity, keep the enzymes happy and everything falls into place.

    One of the peculiar characteristics of this enzyme is that it comes irreversibly inhibited by the molecular oxygen (O2); and since fixation is a process that happens in an aerobic environment, it creates an apparent paradox. In reality, cyanobacteria are able to negotiate the activities of nitrogenase, an enzyme which is essentially anaerobic, with the inevitable presence of oxygen (resulting from photosynthetic processes), through not yet well-known mechanisms. In the marine environment, the nitrogen-fixing bacteria (some of which also belong to Clostridium and Azobacter genera) can be found both in free form and in symbiosis with other organisms (ex. Sponge).

    And ofcourse again enzyme activity achieves denitrification

    Denitrification is mainly a heterotrophic option and occurs in anaerobic conditions. A wide range of bacteria called precisely denitrifying bacteria are able to carry out the entire sequence of reactions, being equipped with a complete enzyme apparatus.
    The denitrifying bacteria are able to accomplish the anaerobic respiration of nitrates by using the nitrate in place of oxygen, as acceptor of the electrons released during the respiratory process. These bacteria possess special enzymes (Figure 3), as the nitrate reductase (NAR) and nitrite reductase (NIR), which allows the electrons to flow towards nitrate or nitrite, in the absence of oxygen. They are flexible enzymes which form in the cellular membrane only under anaerobic conditions: as a matter of fact, a part of NAR, the reductase synthesis is inhibited in the presence of oxygen.

    Enzymes are destroyed when pH is below threshold, i cant say exactly but read somewhere that its is damaged at pH lower than 6.8...or sudden swings in pH.
    Also all this relates to hydrogen + ions.....linked to alkalinity, the availability of hydrogen + ions makes it easy for these ions to do their job as pH will remain stable when their is a good stable supply of hydrogen ions.
    So maintaining a high alk is linked to this, if you maintain this then both carbon and oxygen cycle will find equilibrium.

    In a closed system that means dosing, dosing an dosing.

    Do i make any sense....:) or is it blah blah blah
     
    Last edited: 1 May 2011
  8. Reef Maniac

    Reef Maniac MASA Contributor

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    Stretching my 1974 first-year bio-chemistry a bit :eek:, but yes - you do make sense :)

    What it boils down to is that we need to manipulate the O2 content (sand bed depth), water parameters (pH, Alk...), and many other "things" (keeping the enzymes happy with a tot of vodka ever night... :biggrin:) to allow equilibrium to be achieved at a state where NO3 can be converted to N2, and not back to NH4.

    @SchyffS what's your take on the suggestion of Figure 7 that one should keep the bed depth to a thickness that will maintain the "suboxic" zone, rather than the "anaerobic" zone? As a hobby, I believe that we have been doing just that in practise, but this is the first time that I've seen the NO3 to NH4 pathway shown specifically in the latter zone.

    Aragonite is said to slowly dissolve near the bottom of the sand bed due to lower pH, thus adding calcium, but the lower pH would also inhibit denitrification - so, if the bed is deep enough to add calcium from aragonite, it is too deep to allow denitrification... hmmm :whistling:

    Hennie
     
    Last edited by a moderator: 26 Nov 2015
  9. maxisoft

    maxisoft

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    Intersting article... thanks dallas...:peroni:
     
  10. SIMS

    SIMS

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    All my systems have a dsb :p
     
  11. Reef Maniac

    Reef Maniac MASA Contributor

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    As do mine :thumbup:

    And it's worked just fine during the past 13 years, so I have no reason to want to change it either :whistling:

    Hennie
     
  12. seank

    seank

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    And it is way cheaper than the techno stuff ;)
     
    Last edited: 2 May 2011
  13. SchyffS

    SchyffS Reef Aquarist

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    @ manic....the depth at a point where ph is low enough to disssolve aragonite would inhibit denitrification. The norm(from hobyist) has always been 150mm depth for effective denitrification zone, i suppose any deeper would reach anoxic levels...imo

    I would geuss that an mV proble in suboxic zone would typically read -350mV and in anoxic zone could read >-350mV....again i am just trying to apply some logic in a way to measure this.
     
    Last edited: 3 May 2011
  14. Falcon

    Falcon

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    NP pellets has yet to prove itself,probiotics etc just too much to do maintenance wise compare to a dsb so regardless of trends I don't think the good ol DSB will die off anytime soon for non extreme reefers.

    I'm leaving out a dsb in my new system because i want a more tweak-able low nutrient system,but DSB would still be the most stable long term solution IMO for most tanks and reefers that want a cheap and low maintanance nitrates control method.(still have to use additional phosphate removal systems with a dsb though)

    It works great in low maintenance systems and provides stability once it has matured sure,in sps dominated tanks that want WOW colouration it can be beaten by other methods that ziyaad mentioned above....but I'm sure nobody wants to dose vodka everyday for over 13 years:p so yes in the long run i rate a dsb as the best option currently.

    THAT single point is very important IMO reefers spend too much on the latest hype product without big advantages over what a dsb can do for almost free!



    Still my only gripe with a dsb is that its so good at keeping your nitrates down that you tend to forget about the phosphates which it cant handle...carbon dosing does seem to take care of both in a balanced way,and that I feel is a DSB's weak point IMO



    hennie how do you keep you PO4 in check?
     
  15. Falcon

    Falcon

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    ziyaad do you know of any tanks running long term with no nutrient issues on NP pellets and nothing else?

    According to most manufacturers NP pellets wont take care of your phosphates either so i dont understand why everyone wants that over a dsb?

    I'm really keen on going the NP pellet route in my new tank so trying to find as much proof as i can before i commit to what so far seems more a pipe dream than a practical solution.
     
  16. Reef Maniac

    Reef Maniac MASA Contributor

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    Oh, my cyano does it for me :biggrin: :biggrin:

    Actually, I drip kalk 24/7 very close to my skimmer inlet, and I do believe that helps some. Apart from that, I rely on a good growth of algae in my sump (macro and hair), and I also run RowaPhos when needed.

    Hennie
     
  17. 459b

    459b Moderator MASA Contributor

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    My biggest concern with an ULNS with carbon dosing etc etc is that it relies too much on skimming and dosing. This to me is running your system on a knife edge. Unfortunately our country experinces too many power cuts and i feel one needs the safe buffering of a natural system (ie. DSB and fuge). People tend to forget that bacteria are live organism that require alot of oxygen and nutrients.
     
  18. Falcon

    Falcon

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    I agree it is running the system on the edge but i dont think a fuge on its own is the answer

    My reason is not power failures but rather the macro algae failures in itself,when i started reefkeeping i only used caulerpa to control nutrients in the first few years and I had it randomly die off three times.The once it was caused by an accident where my nephew threw in all sorts of stuff(nesquick,ink,tin of fish food and a plastic nemo for good measure:p) into the sump,but the other two occasions it just withered away for no apparent reason in a day or two and this then lead to nitrate and phosphate build up in the ensuing weeks.(24 lighting in fuge and no elevated amonia when this happened so i don't think it went sexual)

    Yes it was not a train smash when it happened on the two normal occasions but it left me with the realization that a fuge is not as stable we would like it to be and there are a number of factors that could easily lead to its demise,hence a fuge can be a secondary nutrient control method IMO but not the primary as if it fails then you will be running to quickly find other methods in a rush.

    I then went the DSB route and this has from the second month kept the nitrates down for years now without fail,but even though it stopped gha algae etc from growing it still allowed my po4 levels to climb and the po4 saturated my live rock(i only realised this once i had cyano outbreak) then all po4 removal technics did not help with the cyano i had for months on end.


    In my new tank i will use a fuge as a secondary filtration method(and to get tangs some fresh greens now and then) but i'm still thinking of carbon dosing or NP pellets as a primary removal for nitrates and phosphates.

    So the combination could do what you said,use the fuge as a buffer,but not main nutrient control.

    One question,would you guys say the lack of oxygen affects the caulerpa less than it affects the bacteria in the event of a power failure?
     
    Last edited: 4 May 2011
  19. Falcon

    Falcon

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    :biggrin: eish how i hate cyano!

    You using kalk with vinegar or just plain old kalk,i'm thinking of using a kalk and vinegar combination for sorting out nutrients and calcuim requirements,sort of killing two to three birds with one stone(nutrients,calcium,alkalinity) as the vinegar will provide the carbon source.

    And then maybe just a little bit of caulerpa for fun.

    Now my main concern is can i make up a weekly batch of kalk/vinegar and expect it to be in the same state/concentration after five days once mixed with fresh water,or will there be bacterial growth in the holding container using up that carbon source before it gets to the tank later in the week?
     
    Last edited: 4 May 2011
  20. dallasg

    dallasg Thread Starter Moderator MASA Contributor

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    well this also boils down to 3 types of reefer's

    purists
    chemists
    hybrid

    i have been the top 2 and now going hybrid

    my new system will have sump 1 just with a skimmer and floss and then zeolith reactor, then flow into a dual-sump setup(LR and crypto zone), then return.
     
  21. maxisoft

    maxisoft

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    Will be watching with great interest....
     
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