# Understanding Uptake of NPK



## Jason Baliban (Feb 21, 2005)

I am working on a bit of a project here.

If we look at uptake of macro nutrients throughout the week. Lets say we express uptake as percentage of dosage. For example: If I dose 100ppm of N in my aquarium and at the end of the week my reading is 70ppm, then we can say that we have 30% uptake.

How does this percentage vary from macro to macro? Are you finding that you have a certain percentage of uptake across NPK, or are you finding that each nutrient has a different percentage?

What is your current uptake percentage in your tank?

The goal of this is to categorize uptake into 3 categories: Low, Medium, High. To accomplish this, please include your percent of uptake and your tank setup.

The outcome of this will be great for all of us when I am finished with my project.

Trust me.

Thanks

jB


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## Bert H (Mar 2, 2004)

Seems to me you have a lot of variables to take into account here. Things like fish load, how much you feed, your lighting, CO2 or not, to name the ones that come to mind quickly. It also means doing a lot of measuring. 

I tried to calculate some NO3 and PO4 uptakes in my tanks a while ago, and decided why bother. I do EI and as the title says, it is 'Estimative'. 

FWIW, I 'seem' to have low NO3 uptake, but I also have a fairly large stock of fish which are well fed daily. I typically dose 10ppm of NO3 a week and 3ppm of PO4 and nitrates remain in the 10-20ppm range in my tanks using this method.


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## Jason Baliban (Feb 21, 2005)

Thanks for the $.02 Bert....

I agree that there are a ton of factors. And in no way do I think this is going to be an easy answer. But i appreciate you jumping in. Perhaps we can get a fairly good idea if a lot of people put in their 2 cents.

Thanks again

jB


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## MatPat (Mar 22, 2004)

Back when I was using PPS, my 75g was using ~1.6ppm of NO3 per day and ~0.15ppm of PO4 per day. I now dose my tank with about 2ppm of NO3 daily and 0.6ppm of PO4 every other day. I guess that would put me at about 75% uptake on NO3 and 50% uptake on PO4. 

When I first started trying to increase my PO4 to 2ppm I had troubles getting it that high. I guess luxury uptake may have played a part in the first few days/weeks. 

I haven't tested any tank parameters, with the exception of pH and KH, since June or July. It requires more time for testing than I care to spend right now since I have 4 high light tanks. The reagents (LaMotte) get expensive also. I have no idea how much NO3 or PO4 my other tanks use.


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## czado (May 26, 2005)

I think looking at percentages for uptake is flawed and better to look at ppm and/or raw weight. For example, if your system uptakes 30ppm NO3, it would effectively do so whether you dosed 50ppm or 100ppm, assuming all other variables are constant.

My data may not be relevant because I use a reverse photoperiod fuge, but I dose 35-40ppm NO3 and ~5ppm PO4 per week. My targets after dosing are 10-15ppm NO3 and >3ppm PO4 (and have not beaten greenspot). Like Bert I use EI and do not care about excess. These numbers were with a high light 8g + a medium light 10g (fuge) with >40ppm CO2 (DIY).


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## Edward (May 25, 2004)

MatPat said:


> Back when I was using PPS, my 75g was using ~1.6ppm of NO3 per day and ~0.15ppm of PO4 per day. I now dose my tank with about 2ppm of NO3 daily and 0.6ppm of PO4 every other day.


 Did you use K2SO4, KNO3, KH2PO4 and MgSO4 in those 14 PPS days?

Edward


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## Edward (May 25, 2004)

Hi Jason Baliban
The nutrient uptake rate divided by elements doesn’t work like that. I would suggest you read about mobile elements, immobile elements and luxury uptake.

Thank you
Edward


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## MatPat (Mar 22, 2004)

Edward said:


> Did you use K2SO4, KNO3, KH2PO4 and MgSO4 in those 14 PPS days?


I did


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## anonapersona (Mar 11, 2004)

Jason Baliban said:


> I am working on a bit of a project here.
> 
> If we look at uptake of macro nutrients throughout the week. Lets say we express uptake as percentage of dosage. For example: If I dose 100ppm of N in my aquarium and at the end of the week my reading is 70ppm, then we can say that we have 30% uptake.
> jB


Or maybe we can say the uptake is 30ppm per week. Or maybe it is 33% of the nitrate above 10ppm. Or maybe it is 10ppm per day when the total nitrate is above 80ppm and then only 2ppm per day after that.


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