NO3 and denitrification

PatrikS

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Jun 4, 2006
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Tom, another question I started to ask myself, and we already talke a bit about it in previous thread, but I wanted to break it out to a new thread.

I understand that marine macroalgae seems to have a slower uptake rate of nitrogen then freshwater plants. Therefore, the KNO3 doses should be lower.

But on the other hand I observe quite a lot of small bubbles raising from my DSB to the water surface. And I see a lot of bubbleformation in the sandlayer close to the tank's sides. As I understand it must be denitrification going on there. It means that my substrate - and probable some live rocks - "consume" some of the dosed KNO3.

So maybe - just a speculation - we could dose quite more KNO3 to compensate for denitrification? Is it safe for fish and invertebrates (corals aside) to dose say about 20 ppm NO3 in a macroalgea-only-tank?? Why should the NO3-dosing should be lower?

Any thoughts?
 

Tom Barr

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Jan 23, 2005
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Well, adding more NO3 to such tanks may be required.
But how much is likely different based on a few factors, light/temp, roots, stability of dosing, other nutrients required for the bacteria/macros/plants etc.

Overall, it does likely represernt a good size fraction I'd say.

So it's not all going into plant biomass in other words.


Regards,
Tom Barr
 

PatrikS

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Jun 4, 2006
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I increased the KNO3-dosing. The dose was just a little less then 1/10 of a teaspoon.

I observed a lot of bubbles on everything, not just in my DSB.

I see bubbles rising from the substrate to the surface, a couple of bubbles every few minutes.

I see bubbles on the rocks.

Bubbles on the pestalgae.

Macroalgae with bubbles.

It's like Christmas everywhere in the tank! It kinda reminds me of my freshwater high-tech, but it cant possible be fotosyntesis that produce bubbles?? It must be denitrifying bacteria, right Tom?

I will wait and see if the bubbles are present tomorrow, before the lights go on. If i still see the bubbles with no light on, then it must be bacteria, if the bubbles appear when the halide go on, then maybe it has something to do with fotosyntesis...

Kind of scary actually - its beatiful and all, but I would like to know why I have them (bubbles).
 

Tom Barr

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Probably a few things.
1. N limited tank, not good anyway.
2. Increase of O2 production and N2 gas production
N2 not very souble nor sticky, O2 sticky, and somewhat soluble(but not compared to CO2) O2 might increase CO2 in bacteria, O2 bubbles maybe sticking to other things.

Regards,
Tom Barr