# Light intensity effect on NO3 to PO4 ratio



## dennis (Mar 1, 2004)

Well, I mixed up some new batches of Macros the other day and something struck me as odd. Man, in the past I thought I used more PO4 to mix my stock solutions. Let me double check I said....Math has never been my friend. I double checked my little calculations notecards, the formula written on my dosing bottles and I even specifically remember amounts in grams from the past. I double check these against the New Fertilator as well as the old standby, Chuck Gadds, download calc. Check this out...

I was mixing, for atleast the past several months.......2.9grams of KH2PO4 in 500ml of H2O . Turns out that dosing 10ml of that 4x a week to a 10 gallon, if you go by actual gallons 8.2, is 6.2ppm PO4 a week. For nitrates I was mixing 31grams of KNO3 in 500ml H2O, 10ml 4xweek turns out to be 40ppm NO3 in the same 10 gallon tank.. A few weeks back I thought I would try leaning up on my ferts so it turns out I leaned up to dosing 2.6ppm PO4 and 40ppm NO3. 

I wonder if the dirtyness and the seeming imbalance to my tanks is due to the extra nutrients and imbalance of ratios of the nutrients? I know, I know, excess nutrients do not equal algae but still, high nitrates do tend to make everything "dirtier" and things can go downhill pretty fast, IMO. I have always fought a slight green fuzz issue about halfway through the week, even a greenspot too. After I leaned up the nutrients a bit, things did go a little smother.

So now I have adjusted my dosing levels and solutions...
20.2grams KNO3 in 500ml H2O and .8 grams KH2PO4 in the same 500ml. My figuring usign both the Fertilator and Chuck's Calc. tell me that 10ml of this solution in a 10 gallon tank(8.2 actual gallons) gives my 8ppmNO3, 5.15ppm K and .375ppm PO4. I dose this 4x week so I am doseing 32ppm NO3, 20.6ppm K and 1.5ppm PO4.

Anyone care to comment? Not sure about what but I am sure this deserves something


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## Edward (May 25, 2004)

Hi Dennis

Your 10 gall dosing would be an equivalent of daily dose of 1ml SS and 6ml PF solutions. Easy mix, easy dosing routine and the ratio can be changed any time by simply changing the dosing ratio of the two solutions. 

The actual NO3: PO4 dosing ratio is light intensity dependent. Higher the light more NO3 is needed to maintain the proper water column levels. At lower light intensities, more PO4 in relation to NO3 is needed. 

Thanks for sharing
Edward


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## dennis (Mar 1, 2004)

Are you refering to my old doseing or my new dosing amounts? I relation to the light levels and nutrient ratios, what ratios have you found working good for you? I know every tank is different but there must be some common ground, assuming nitrate/PO4 free tap water. I have high fish loads and feed moderately, 2x a day.

I love you PPS method and the only reason I don't use it is because I have not taken the time to invest in test kits and to really sit down and figure it out. Maybe when all the small tanks are gone and I just have the 50......

Thanks for your reply Edward


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## Edward (May 25, 2004)

Hi Dennis

The dose is in reference to your new routine.
The PPS solutions locked the amount of K in relationship to the NO3 and PO4 as a constant. Therefore the K is an element we don't have to worry any longer. It will always be present regardless the dose.
We have to focus only on the other two, the NO3 and the PO4. This is achieved by using the main solution, the SS (Standard Solution) where NO3: PO4: K is at 0.75: 0.25:1.00. This SS solution has the NO3O4 ratio that fits dosing requirements of a lower light aquarium. I call it the standard. 
Because we have aquariums with a variety of light intensities we need to have the option to easily modify the NO3O4 dosing ratio. This is done by combining a low light solution NF (NO3 Free Solution) with the main SS solution. For high light aquariums we combine a high light solution PF (PO4 Free Solution) with the main SS solution.

*Example of a daily dose for a low light aquarium:*
2ml SS
4ml NF

Details:

Total ppm per 100 liters NO3O4:K
0.50:0.50:2.00

Ratio based on NO3
10.00:10.00:40.00

Ratio based on PO4
1.00:1.00:4.00

Ratio based on K
0.25:0.25:1.00

*Example of a daily dose for a high light aquarium:*
2ml SS
4ml PF

Details:

Total ppm per 100 liters NO3O4:K
1.50:0.17:2.00

Ratio based on NO3
10.00:1.11:13.33

Ratio based on PO4
9.00:1.00:12.00

Ratio based on K
0.75:0.08:1.00

We can see above how easy dosing routine this is. By simple usage of two solutions we can administer the complete NO3 PO4 and K fertilization process.

*References: * 
_Perpetual Preservation System v.2005
PPS Analysis and Feedback _

Thank you
Edward


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## plantbrain (Jan 23, 2004)

Edward said:


> Hi Dennis
> The actual NO3: PO4 dosing ratio is light intensity dependent. Higher the light more NO3 is needed to maintain the proper water column levels. At lower light intensities, more PO4 in relation to NO3 is needed.
> 
> Thanks for sharing
> Edward


From everything I've seen, tested and read, under non limiting conditions, the ratio of N will be the same in terms of their biomass at a variety of lighting levels hobbyists use.

I've seen rather similar uptake rates of NO3 and PO4 at a variety of light intensities, and with non CO2 tanks as well.

I have not seen an increase in NO3 uptake relative PO4 uptake as light intensity increases. A number of Danish researchers did studies on aquatic plants to this effect(they did the dry weight anaylsis for conformation) as well as as my own test which assumed the NO3/PO4 was used by plants.

Perhaps the plant species were different?
Perhaps the fish loading was different?
Fish food is often heavy in N, light in P.

I often test tanks without any critters or fish to rule that out. 
Plant species and biomass are easy to test, use Riccia (no substrate needed thuis less denitrificational loss) and do wet vs dry weight or % removal of the nutrient. Then try communities of plants.

Plants are selectively different in their N ratios, the range is quite wide.
Is it the light or is it the plant species composition?

This will take time and need many plant tanks and species to be compared to see if there is a pattern. I've tested tanks for many years already with these questions in mind.

I might not have the same plant species or density as you, but I cannot say I've seen a correlation between light and increased ratio of N/P.

Dennis, the new dosing routine is about right (add a tad more PO4 or PS), add about 2 mls of traces 3x a week as well and as always, add more CO2, especially if you have algae and clean it out.

Regards, 
Tom Barr


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## Edward (May 25, 2004)

plantbrain said:


> From everything I've seen, tested and read, under non limiting conditions, the ratio of N will be the same in terms of their biomass at a variety of lighting levels hobbyists use.


 Hi

We are not talking about *biomass* here. We are discussing daily dosing ratios in a quest to maintain stable measurable NO3 and PO4 water column concentrations.

If the constant N ratio theory was correct then we would already have *The Magic aquatic plant fertilizer*. Unfortunately that's not the case. Many members are still trying to mix their own solutions in hope finding it one day, changing ratios again and again. The PPS system has achieved that by the use of premixed solutions. The Standard (SS), Low light (NF) and High light (PF) solutions.

Many are using the PPS today in a variety of lighting conditions from 0.75 Wpg to 6 Wpg. Why the dosing requirement ratio is not the same for all the aquariums?

Thank you
Edward


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## plantbrain (Jan 23, 2004)

> Hi
> 
> We are not talking about biomass here. We are discussing daily dosing ratios in a quest to maintain stable measurable NO3 and PO4 water column concentrations.


Okay then, where does the NO3 and PO4 go? Take the next step.

There will always be variation in a ratio, I've do not endorse a particular ratio either, they really are not particularly critical nor have I ever said there's a magic plant fertilizer.

K+ constant levels are not important if the K+ is in a rather wide ranging excess level, you also do not have to worry about K+ either in that case.

In the quest for the stable NO3, PO4 level, folks can hit an effective range and do with PPS and with EI.

Plant growth rates change, biomass(thus uptake rates also change) changes and shading etc. 
Both address it.

Both can play around with different ratios to their heart's content.



> Many are using the PPS today in a variety of lighting conditions from 0.75 Wpg to 6 Wpg. Why the dosing requirement ratio is not the same for all the aquariums?


Same reason as it is for EI, plant difference, not all plants have the same need or abilty for luxury uptake for a certain ratio.

As folk keep plants longer and take these measurements, they will see patterns, an average, they tend to be similar at diffenent light values IME and in the research. Individual tanks might vary. I'd not rush to a conclusion that low light tanks need more or less NO3 or PO4 ratio.

Fish loading, different plant species, density, true light readings(eg micro moles), all will slant the ratio and needed dosing with PPS/EI.

It's something that was not pointed out and is critical.
A lot of the nitrogen will never be tested from fish waste since the NH4 is used before you can measure it.

You can see an indirectly uptake rate in terms of NO3(consider total N uptake), but it's mildly correlated.

You might want to consider some of these issues.

Regards, 
Tom Barr


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## Edward (May 25, 2004)

Hi Tom

Asking where does the NO3 and PO4 go? 
Well, if NO3 was bolts and PO4 nuts and we were building a bridge then we have an issue. En exact number of nuts fit the number of bolts we use for the structure. There is no way around it. The ratio is fixed. 
However, plants don't work that way. Plants have the ability to shrink, stretch and substitute material to build their structure. We call it * Luxury Uptake *. This is not a myth, this is a fact.

Do you think that the same plant specie grown in very different conditions would still have the same NO3 to PO4 dry analysis ratio?

Thank you
Edward


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## plantbrain (Jan 23, 2004)

Edward said:


> Hi Tom
> 
> However, plants don't work that way. Plants have the ability to shrink, stretch and substitute material to build their structure. We call it * Luxury Uptake *. This is not a myth, this is a fact.
> 
> ...


Hi Edward, 
I was mentioning that plants do have variation in their uptake of both of these nutrients.

I suggested luxury uptake, I suggested plant species differences, I also suggested fishload nutrient sources/differences.

That was the point.

As you gain comparisons of many tanks over time, plant species under different light intensities, the generalization is fairly standard, I find the plants keep relatively similar ratios.

You claim that they don't.
A few cases maybe, but as you test more and more tanks, plant species etc, the pattern you have seen may not be that more light requires more NO3, less light requires more PO4.

Another issue in PO4/NO3 uptake:
NO3 uptake is inducilble and have both low and high affinity transportors, PO4 uptake transportor tend not to be inducible.

So the concentration of NO3(different concentrations of NO3 will induce one or both enyzyme transportors), the presence of NH4 and other factors greatly influence whether NO3 is removed at a higher rate or not as well as PO4 levels.

These issues will play a role in using PPS/EI and extending the water change frequency/volume further out.

In any event, Dennis simply needs more PO4, CO2 and clean the tank and tend it more.

Regards, 
Tom Barr


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