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Nitrates Struggle

Discussion in 'Aquatic Plant Fertilization' started by acinonyx, Jan 5, 2018.

  1. acinonyx

    acinonyx Member

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    Guys,

    I have this problem I have been battling for several weeks now and I cannot wrap my head around it.

    I keep dosing >50 mg/L weekly total (in 7 doses, each day) and my nitrates are always <2 mg/L. Yes, I am shaking the test vial really well. I don't think the test is wrong either since, I am always getting quite a bit of BGA as the water change approaches. Also, I am observing pale new growth and some hair algae, which in my opinion really points to a low nitrate issue. No matter what I do, I can't really increase my nitrate levels.

    My tank has soil capped with quartz sand if it makes any difference.

    Have you ever observed something like this? Is it even possible to have such a high consumption? Could there be denitrification going on somehow?

    Peter

    EDIT: The tank is heavily planted.
     
    #1 acinonyx, Jan 5, 2018
    Last edited: Jan 5, 2018
  2. Phishless

    Phishless Lifetime Member
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    Calibrate NO3 test kit first.
     
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  3. acinonyx

    acinonyx Member

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    I am a chemist. Trust me, this is not test kit issue.
     
  4. Allwissend

    Allwissend Article Editor
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    Is the NO3 source confirmed ? I think the idea of @Phishless is so that you check if you add a known amount to a known volume of distilled water, do you get the concentration you expect (or nearby). Some vendors sell non NO3 compounds under false labels, other sell a blended mix. Worth a try, if you know the test kit works well.

    How old is the soil ? Did it go really anaerobic ? It is unlikely that you will have this rate of use. Maybe if you have aerial plants with the roots in the aquarium ?
     
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  5. acinonyx

    acinonyx Member

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    The source of NO3 is confirmed. It's from my lab. I also checked the content of NO3 in my tank water using FDA approved method for determination of nitrates (spectroscopically). So I am 100% sure I have VERY low nitrates in the tank.

    Regarding the soil, I am not really sure. This is my first tank using capped soil. I don't see any bubbles of gas (i.e. H2S) if that's what you are asking. The tank is about 10 months old now.
     
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  6. Allwissend

    Allwissend Article Editor
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    Good, now that the simple to fix stuff is confirmed, the interesting stuff begins :D

    Hmm yes H2S, CH4 and other gasses may be produced as bubbles when the substrate is anaerobic, but it is not mandatory to see the bubbles. Looking for darker areas is a better way. Outside plants, an anaerobic substrate would be my guess.
    Then I would go look in filter media or hardscape material (lava rock can also go anaerobic deep in the pores) .

    It might be worth providing more details: photo of the aquarium, plant list, water and aquarium parameters, filter type and media, fish ...

    Some pathways worth exploring : What happens when you add more NO3 (say 10mg/L in one day) or when you add urea instead? What happens when you run with an empty filter ? What is the uptake profile after a dose in light / dark conditions ?

    Maybe other members with soil tanks have more ideas. Interesting observation @acinonyx . Hope you find the answer.
     
    acinonyx likes this.
  7. acinonyx

    acinonyx Member

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    I will upload the photo when I come home. Needless to say, pretty much every inch of the tank is planted. Darker areas...well... difficult to say since the sand is black. :D

    I suspected something funky might be going on in the pumice that I have in the external filter, so I already removed it. There is still the original JBL "microporous" media left in, though. Maybe I could try to remove that one for a while as well and keep only the foam. Urea is something I have also considered, since plants would have more time to take it in before it is hydrolyzed to NH4+ and possibly "denitrified".

    Well, at least my assumption that such high uptake would be unrealistic proved to be correct. I will try to figure out the cause, and I will start with the filter media.
     
  8. fablau

    fablau rotalabutterfly.com
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    What's your used substrate?
     
  9. acinonyx

    acinonyx Member

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    The soil is this, about 1/2 inch at the front glass and 1 inch at the back:

    https://www.prohopo.cz/image/products/big/1761.jpg

    Capped with a regular black quartz sand (1-2 mm), 1-2 inch layer.

    Here is a crappy and blurry cell phone shot of the tank. You can see the BGA on the Monte Carlo in the front:

    26653326_10212526948386749_1384872651_o.jpg
     
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  10. Phishless

    Phishless Lifetime Member
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    No lies on lots of plant mass!:D

    I use capped soil and some weeks require 2x EI macros or more.
    Not only does NO3 fall quick so does PO4 for me.
    If I do a serious trim and plant mass is greatly reduced I dose about half EI for a week.
    This could be all uptake from plants.o_O
     
  11. Kyalgae

    Kyalgae Lifetime Members
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    Algae aside, I really like that layout, that java fern looks like some deadly creature. Those two anubias at the front really...they make my eyes go ‘yes’.

    I know your tank is old but could things be decomposing somewhere? Nitrogen robbing when things decompose is a thing (its late....) I know when you do hugelcultur you need extra nitrogen so the wood doesn’t steal it all from the plants when it starts to break down. https://permaculturenews.org/2012/01/04/hugelkultur-composting-whole-trees-with-ease/ I was trying to find the mechanism, but I can’t find out why the wood needs the nitrogen, maybe the local bacteria? It looks like it’s the bacteria. https://www.planetnatural.com/composting-101/making/c-n-ratio/ Just throwing some ideas out there. I wonder where all the nitrogen is going? Aliens?
     
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  12. acinonyx

    acinonyx Member

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    Haha, thanks! Well the tank is usually not that overgrown, and the BGA issue is not that bad. This shot is after two weeks Christmas holiday, right before maintenance.

    Anyway, something like that is what I am suspecting? Under hypoxic (low oxygen) conditions (usually when something is rotting, i.e. soil in the substrate), you can get conversion of NO3 to N2 (denitrification). Well there are also cases of denitrification under ambient conditions, but they are quite rare.
     
  13. fablau

    fablau rotalabutterfly.com
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    Nice tank indeed. Those algae got to disappear. I am pretty sure the dirty cap is the No3 sucker. I wouldn't worry about that mug, just dose the standard EI dose and you'll be fine. And yes, I also second the advice to reduce plant mass and keep up with WC, and possibly reduce light to help plants vs algae. Double check the rest as well (micro dosing, Co2, clean filters, not feed too much, shallow vacuum the substrate, etc... Regular maintenance routine)
     
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