# Uptake rates



## Edward (May 25, 2004)

Why are some people so obsessed with uptake rates? What difference does it make?

Edward


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## zeek (Jan 5, 2005)

Without knowing the uptake rate of our tanks how are we supposed to know how much fertilizers are needed to replentish? If dosed only once a week, there is deficiency. If dosed blindly every day a crash is inevitable.


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## MatPat (Mar 22, 2004)

I think maybe some folks are just interested in knowing their uptake rates. Aren't uptake rates used for calculating how much of each solution you add when fertilizing via PPS?


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## Milan (Jul 6, 2005)

My understanding is that neither PPS or EI focuses on uptake rates, and ferts dosing has nothing to do with it... On the other hand, some people may have interest in (obsessed with) such things, but it is mostly unlikely that would apply to an average hobbyist ... I don't even know how would you determine uptake rates without some serious lab analysis ...


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## anonapersona (Mar 11, 2004)

If I dose to 8 ppm nitrates on Monday and on Tuesday it is 3 ppm, then I know the uptake rate. If my plants will consume 5ppm nitrates in 24 hours, I may need to dose nitrate every day. Or dose more. I think that is worth knowing, for I will not be doing water changes every day to reset the tank.


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## Milan (Jul 6, 2005)

anonapersona said:


> If I dose to 8 ppm nitrates on Monday and on Tuesday it is 3 ppm, then I know the uptake rate. ...


You don't. You neglected the organic portion, which is not static ....


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## anonapersona (Mar 11, 2004)

Milan said:


> You don't. You neglected the organic portion, which is not static ....


Why not? Assuming that I feed pretty much the same sort of stuff daily, the same fish are in the tank, the lights are on the same schedule, and the filters are not significantly cleaner or dirtier in that time frame?

Heck, I'm not trying to be exact, I don't care to be exact... I can't tell that much on the test results anyhow, it reads 0ppm, 5ppm, 10ppm, 20ppm. I just need to know in general how it is going, if indeed it reduces, when I need to dose again and how much.


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## Milan (Jul 6, 2005)

Well, ... if you are settled with knowing the residual levels of your nitrates, ... that's fine, but you can't draw the "uptake rate" from it. You don't know how much of it is produced vs. consumed by plants, regardless of your feeding routines.


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## anonapersona (Mar 11, 2004)

*nominclature*

So, is it just the way we name this that is the problem? Instead of "uptake rate" of nitrate, how about "rate of change in residual" of nitrate? Makes no diff to me, I just want to know what to dose and when.


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## Milan (Jul 6, 2005)

Sorry, I didn't mean to pick on wording, ... it's just how I perceived the Edward's question. What you are doing is exactly what PPS is all about. Measure and dose.


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## AaronT (Apr 26, 2004)

One thing to consider when calculating dosing requirements is any change in plant biomass. For example, if you've just trimmed out the entire tank and are waiting for lots of stems to grow back they won't consume near the nitrates they will in a week once they have branched and grown back.


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## plantbrain (Jan 23, 2004)

Milan said:


> Sorry, I didn't mean to pick on wording, ... it's just how I perceived the Edward's question. What you are doing is exactly what PPS is all about. Measure and dose.


I measure with a teaspoon and dose for EI. Is that PPS as well?
What is PMDD+PO4? Folks have done this for many years long before EI or PPS.

A tank's consumption daily, weekly etc, is not all plant uptake: algae, bacteria, detrial material, water changes, degassing, roughly 4 to 5 nitrogen transformations can occur.

As mentioned also, plant biomass changes can be dramatic, this directly influences uptake rate.

So does light, so does CO2...........

You add these variables in there and some test kit error........now I begin to question what good are the rates .......unless you look at max rates.

That at least tells you something useful so you do not need to test any longer once you get that standard. Adding more is never needed. the plants always have plenty of nutrients available. You can add less and tweak as needed. You can test and add replacement nutrients.

Rates are important since they tell the owner when they need to tend things.
But they do change a fair amount though time and with the various changes we do. That's something I know I do not need to chase till the end of time once I figured out what some max typical rates are.

Regards, 
Tom Barr

www.BarrReport.com


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## Milan (Jul 6, 2005)

plantbrain said:


> I measure with a teaspoon and dose for EI. Is that PPS as well?
> What is PMDD+PO4? Folks have done this for many years long before EI or PPS.


What I meant by "measure" is using test kits to measure nutrient levels, and dose ferts accordingly. This is PPS. Perhaps I shouldn't have mentioned PPS (or EI), since it's leading to another debate about fertilization approaches, which would in my mind sidetrack this thread.

My point was that the uptake rates in their true meaning are unknown in the domain of an average hobbyist, and as such irrelevant. Either you want to dose ferts using teaspoons, or mls of fert solutions, it doesn't matter, ... as long as you don't allow nutrients to bottom out.


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