# Fertilizer uptake at night (nitrate)



## Tugg (Jul 28, 2013)

Do plants continue to uptake nitrate or other ferts at night? I have a 55g with a 55g sump that has about a half gallon of Pond Matrix as biomedia. I checked my nitrate shortly after lights out, and shortly before. It went from 10-20ppm to 0. Either the Pond Matrix work way too good, or the plants keep eating. I am wondering if I need to pull out the Matrix since it seems its removing a LOT of nitrate.


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## Zapins (Jul 28, 2004)

Basically I think this is what you want to know:

Summary

PO4 is taken up in the day and night, but much more is absorbed in the light. PO4 is also preferentially taken up by shoots and roots.


Ca and K are both absorbed in light and darkness but more during the dark.


Mg is absorbed almost equally in light and darkness.

Phosphate and nitrate uptake thread:
http://www.aquaticplantcentral.com/...87693-nutrient-uptake-night-2.html#post659666

Phosphate uptake in aquatic plants paper:
http://ir.ihb.ac.cn/bitstream/34200...ersed macrophyte Myriophyllum spicatum L..pdf


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## Tugg (Jul 28, 2013)

Good reads. Still isn't clear on NO3 though.



OTPT said:


> Just stumbled upon this.
> 
> http://www.waterboards.ca.gov/water...lta/docs/cmnt081712/sldmwa/feijooetal2002.pdf
> 
> "A preference for amrnonium over nitrate has also been observed in other subinerged macro-phytes, such as Ceratophyllum demersum (Toetz,1971) and Myriophyllum spicatum (Nichols &Keeney, 1976b). In C demersum, nitrate uptake has been found to correlate with light intensity,practically ceasing in the dark, while ammonium uptake was continuous and decreased only slight-ly at night (Toetz, 1971)"


This would imply that nitrate isn't taken up at night, but I'll want to read the article. If NH4 is present during the experiments it could be that NO3 was taken, but bacteria converted a near equal amount of NH4 to NO3. Its ironic, I would hate to find out that the Pond Matrix is working too good.


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## Zapins (Jul 28, 2004)

Hmm yes it does seem to imply that I'll have a read through it and maybe a few of the sources.

Not sure what Pond Matrix is made of but I think it could probably suck up some nitrates. Maybe the others were sequestered somewhere else.


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## Tugg (Jul 28, 2013)

Pond Matrix is a larger version of Seachem's Matrix. Its basically pumic gravel that works like live rock. The size allows for anaerobic bacteria to form on the inside. I bought it before I became obsessed with planted tanks.

I wouldn't be surprised if this is it. Seachem sells good stuff. I just may be an example of a bad application of it. The stuff would be awesome for large cichlids or other non-planted tanks.

I'm just hoping it isn't the media, and its the plants instead.


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## Yo-han (Oct 15, 2010)

I asked the same question on this forum before. Try finding it. The short answer is yes, it is taken up at night. Do a 3 day blackout and measure NO3 before and after and you'll see it is reduced


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## Phil Edwards (Jan 22, 2004)

Matrix is a denitrification medium designed to facilitate conversion of nitrate to nitrogen gas. There's a good possibility that that's where your excessive nitrate loss is coming from.


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## Tugg (Jul 28, 2013)

That's my worry. I think it may be working way too good. With my sump, I have twice the volume of water vs plants. The 10ppm that was consumed overnight is equivalent to 20ppm worth of nitrate. That's nuts right?


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## Zapins (Jul 28, 2004)

In my 90g tank with a wall of plants (40% of space filled with plants) I use about 25-30 ppm NO3 per week so yes 10 - 20 gone over night is a lot.

Phil I am curious how does that media change NO3 to N2? I've never heard of any organism that does that conversion.


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## migrans (Nov 1, 2013)

Denitrifying bacteria like Pseudomonas do this job, but if I remember well they should work at faster rate (if not exclusively) in anaerobic conditions, I found this reference if you're interested: http://link.springer.com/article/10.1007/BF00408378 .


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## Tugg (Jul 28, 2013)

Pond Matrix is the larger version of Matrix. The idea is that by the time water has reached it's inner areas the O2 has been depleated. This allows the denitrifying bacteria to setup shop. I just didn't think it worked with such a high consumption rate.

When I get a chance, I'm going to pull it out and see how much of a difference it makes.


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