Nitrate- cannot get it to fall

[CHSUB]

Ratios are a funny thing, I find them completely useless. In nearly all cases hobbyist are using hobby testing which are very inaccurate. If the nutrients are there the algae will consume them. Maybe in the ocean certain species over centuries will gain an advantage, however in a puddle of a reef tank over a couple of years or months?

What would the ratio gurus think of this ratio?

 

[Randy Holmes-Farley Verified Community Expert]

What would the ratio gurus think of this ratio?

I think nutrient ratios as reefing targets are basically an inappropriate waste of math.

I have never seen any reason to not just look at the individual absolute values to assess suitability.

In this case, the nitrate may be fine if there are other sources of N, and not fine if there are not. Since you know from experience with this particular tank that it works, then I expect there are adequate other sources of N. For folks who do not have that same experience with their particular system, I'd want to see nitrate higher.

The phosphate is OK. I'd prefer it a bit higher, but its not what I'd call too low.

 

[EnterName]

now the chaos is perfect:

We have Opinion A saying nutrient ratios matter, even in tanks with higher nutrient levels.

Then we have Opinion B saying nutrient ratios matter more when absolute values are low like in nature but less when they are a bit higher like in most reef tanks.

And now there is Opinion C saying they don't matter and absolute values are the most appropriate measure

I love it

 

[JonasRoman]

I think BOTH ratio and absolut values matter. Ofcourse I say, as N and P are the conductor of our tank, if I exaggerating a bit. The ratio in this example is approx 3.8, so very low, meaning its risk of N deficiency for the zooxanthelle/coral. The absolut value are fine I think.
Reason why ratio matters is that it tells me what will be limiting with further decrease, and here it will be the N. Also it tells me that when coral has used what it need for N there will be a waste of P, that maybe isnt ideal (but must not be bad). I would not lower P but rather have an eye on N and try to increase nitrogen input in that case.
Absolute values also matters, as in very hogh values, those can itslef be bad, where for instande very high no3 may be bad for the coral. Very high Po4 may inhibit calcification, etc.
So for me its both.

Jonas

 

[Randy Holmes-Farley Verified Community Expert]

The absolut value are fine I think.
Reason why ratio matters is that it tells me what will be limiting with further decrease, and here it will be the N.

I don't deny that possible value if one wants to know that. It's not trivial to use, however, since one would need to know in what ratio the values will decline.

 

[Dan_P]

I'm not sure I understood you correctly. Delbeek said a 50:1 N:P ratio worked for tanks? That sounds reasonable I suppose. Unfortunately we can't use the study to check it.

The study tested ratios of 117:1 and 211:1 (both bleached), as well as 22:1 and 1:60, which remained healthy. So nothing is really close enough to 50:1 to give us something to work with here .

We also can't tell the absolute P levels just from the ratio. So if the paper's assumption is correct that ratios don't really matter above 0.03ppm PO₄, we wouldn't be able to apply its findings anyway.

I think the following makes clear why I believe the paper correctly assumes that ratios don't matter too much above a certain PO₄ level anymore.
I calculated the "deadly" 117:1 N:P ratio for various phosphate levels. Nitrate levels above those stated in the table would bleach the corals if the N:P ratio still mattered at phosphate levels above 0.03ppm.

PO₄ (ppm)	NO₃ (ppm)
0.03	2.29
0.04	3.06
0.05	3.82
0.06	4.58
0.07	5.35
0.08	6.11
0.09	6.87
0.10	7.64

I don't think having 0.10ppm PO₄ and 10ppm NO₃ is causing corals to bleach and neither does 0.03ppm PO₄ and 5ppm NO₃ (at least not in my tank #AnecdotalEvidence).

There has to be something to the statement that at some point the ratios don't mean so much anymore in my opinion. Otherwise, many tanks would crash right now.

Edit: Obviously you can go so low with phosphate and/or nitrogen that stuff dies. But that's not what the paper is about, and I don't think anyone is doubting that.

The discussion has not factored in the fact that the large variability in hobby measurement of phosphate and nitrate results in aquarium ratios being all over place. You really don’t know what your ratio is. Let’s drop ratios from the discussion, and focus on the measured amounts of each species.

 

[Dan_P]

now the chaos is perfect:

We have Opinion A saying nutrient ratios matter, even in tanks with higher nutrient levels.

Then we have Opinion B saying nutrient ratios matter more when absolute values are low like in nature but less when they are a bit higher like in most reef tanks.

And now there is Opinion C saying they don't matter and absolute values are the most appropriate measure

I love it

Once you remove opinions and assertions about ratios, which we cannot actually determine with any accuracy, the world becomes simpler.

 

[EnterName]

The discussion has not factored in the fact that the large variability in hobby measurement of phosphate and nitrate results in aquarium ratios being all over place. You really don’t know what your ratio is. Let’s drop ratios from the discussion, and focus on the measured amounts of each species.

It hasn't even factored in that NO₃ isn't the only N source and PO₄ the only P source. So obviously precise N:P ratios are far to complex for hobbyists to measure.

I'm just saying if you can detect at least 0.03ppm PO₄ you are above the study's threshold regardless of other P and N sources and that might explain why we are fortunate enough we can focus on absolute levels and don't need to worry too much about ratios anymore, even if there certainly still is some effect.

 

[Lasse]

Excuse a youngster but in this statement it seems to me that you contradict yourself

hat the large variability in hobby measurement of phosphate and nitrate results in aquarium ratios being all over place. You really don’t know what your ratio is. Let’s drop ratios from the discussion, and focus on the measured amounts of each species.

If you can´t use your measurement in order to get a ratio because large variability in hobby measurement - how can we focus on the SAME measurement of each species? What you say is that we can never relay or transfer a measurement from one testperson/aquarium to another testperson/aquarium


Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

Excuse a youngster but in this statement it seems to me that you contradict yourself

If you can´t use your measurement in order to get a ratio because large variability in hobby measurement - how can we focus on the SAME measurement of each species? What you say is that we can never relay or transfer a measurement from one testperson/aquarium to another testperson/aquarium


Sincerely Lasse

I cannot answer for Dan’s opinion, but here’s one related thought.

If one is looking at ratios, and the phosphate is low enough that the uncertainty in measurements becomes a large fraction of the value (say, at 0.03 ppm or less), then that uncertainty can cause huge swings in the ratio.

OTOH, if one is looking at absolute values, and merely concludes that 0.03 ppm or less is too low, no effects of the uncertainty really come into play.

 

[Dan_P]

Excuse a youngster but in this statement it seems to me that you contradict yourself

If you can´t use your measurement in order to get a ratio because large variability in hobby measurement - how can we focus on the SAME measurement of each species? What you say is that we can never relay or transfer a measurement from one testperson/aquarium to another testperson/aquarium


Sincerely Lasse

Hi Lasse,

I was specifically refering to ratios, not measurements of a single species. A large number divided by a small number when measurements of those numbers are near the limit of detection make ratios a very noisy parameters. Comparison of such ratios between aquaria is likely to be meaningless.

Dan

 

[Lasse]

Yes ratio can vary a lot from day to day but in my case - its mostly because my NO3 vary rather much. What i have notice is that if my average molar ratio is between 15 and 40 - the aquarium looks and works well in my subjective observations. Note that I feed a lot - the calculated input after growth is shown on the second graph

I use both GFO and Denitrification + refugium. I have done nearly 4 months of daily measurements - Hanna Marin Master.

Sincerely Lasse

 

[Dan_P]

It hasn't even factored in that NO₃ isn't the only N source and PO₄ the only P source. So obviously precise N:P ratios are far to complex for hobbyists to measure.

I'm just saying if you can detect at least 0.03ppm PO₄ you are above the study's threshold regardless of other P and N sources and that might explain why we are fortunate enough we can focus on absolute levels and don't need to worry too much about ratios anymore, even if there certainly still is some effect.

I get what you were saying, which seemed to me like declaring “checkmate”.

My assertion is that with crude measurements of NO3 and PO4, the large variability in the resulting ratio makes it totally useless, just noise. That is why I invited everyone in the hobby to forget about nutrient ratios.

 

[Lasse]

Comparison of such ratios between aquaria is likely to be meaningless

Yes - but IMO it is also the case when you compare absolute numbers - especially with PO4 when one person says 0.06 is sweet point and another say - no, no its 0.15. IMO - it could in reality be the same concentration.

Sincerely Lasse

 

[Dan_P]

Yes - but IMO it is also the case when you compare absolute numbers - especially with PO4 when one person says 0.06 is sweet point and another say - no, no its 0.15. IMO - it could in reality be the same concentration.

Sincerely Lasse

I totally agree and that is why I feel strong assertions involving hobby measurements of nitrate and phosphate are like AI hallucinations.

 

[Lasse]

That is why I invited everyone in the hobby to forget about nutrient ratios

IMO - not if you concentrate you around your own aquarium and your own measurements. If so - i think it could be a tool among others. But I will stop to discuss this in this thread. I´m investigate that for the moment - but it will take some time to come to an conclusion

Sincerely Lasse

 

[Dan_P]

Yes ratio can vary a lot from day to day but in my case - its mostly because my NO3 vary rather much. What i have notice is that if my average molar ratio is between 15 and 40 - the aquarium looks and works well in my subjective observations. Note that I feed a lot - the calculated input after growth is shown on the second graph

I use both GFO and Denitrification + refugium. I have done nearly 4 months of daily measurements - Hanna Marin Master.

Sincerely Lasse

Lasse,

Why does the nitrate vary so much? Did the data collection help you come to a conclusion?

Dan

 

[Lasse]

Why does the nitrate vary so much?

I think it is natural variation in my denitrification filter and/or the accuracy of the HR Nitrate method ±2,0.

Did the data collection help you come to a conclusion?

Not to a final conclusion but thank you

Sincerely Lasse

 

[areefer01]

I totally agree and that is why I feel strong assertions involving hobby measurements of nitrate and phosphate are like AI hallucinations.

Why then just nitrate and phosphate? Should we not included any of the other hobby grade results or ICP for that matter?

Traditional hobbyist are somewhat limited to what we can use as you are very much aware of. We are not trying to reach low earth orbit or fly on mars. We have to have faith in how we conducted the test and its result - ratio or not.

Interesting thread never the less.

 

[EnterName]

I get what you were saying, which seemed to me like declaring “checkmate”.

My assertion is that with crude measurements of NO3 and PO4, the large variability in the resulting ratio makes it totally useless, just noise. That is why I invited everyone in the hobby to forget about nutrient ratios.

I didn't know how crude the measurements actually are, so I took the time to calculate it through and see how badly we would actually be approximating the ratios... (the math nerd in me kept me from going to bed. It's 01:00am here)

If you just want the results, ignore the colored part.

The Hanna LR Nitrate checker (HI781) reads 0.00 - 5.00ppm NO₃ with an accuracy of "±0.25ppm ±2% of reading".
The ULR Phosphate checker (HI774) reads 0.00 - 0.90ppm PO₄ with an accuracy of "±0.02ppm ±5% of reading".
Let's say the true values are in the middle of each checker's range: 2.50ppm NO₃ and 0.45ppm PO₄.

The expected readings are then within the following ranges:
NO₃: [2.21; 2.81]
because
2.21ppm + 2.21ppm ⋅ 2% + 0.25ppm ≈ 2.50ppm, and
2.81ppm - 2.81ppm ⋅ 2% - 0.25ppm ≈ 2.50ppm

PO₄: [0.41; 0.49]
because
0.41ppm + 0.41ppm ⋅ 5% + 0.02ppm ≈ 0.45ppm, and
0.49ppm - 0.49ppm ⋅ 5% - 0.02ppm ≈ 0.45ppm

Now convert the readings to N and P masses:
[2.21; 2.81]ppm NO₃ ≈ [0.499; 0.634]ppm N (NO₃ to N by dividing by 4.427)
[0.41; 0.49]ppm PO₄ ≈ [0.134; 0.161]ppm P (PO₄ to P by dividing by 3.066)
True masses:
2.50ppm NO₃ ≈ 0.565ppm N
0.45ppm PO₄ ≈ 0.147ppm P

So we would expect an N:P mass ratio between 0.499 / 0.161 ≈ 3.1:1 and 0.634 / 0.134 ≈ 4.7:1
while the true mass ratio is 3.85:1

Converting to molar/atomic ratios (multiply the mass ratio by 30.974 / 14.007 ≈ 2.211)
we get a molar N:P ratio between 6.8:1 and 10.5:1
while the true molar ratio is 8.5:1
(Shortcut: molar N:P = ppm NO₃ / ppm PO₄ × 1.532)

That's roughly -20% / +23% in the worst case, where both checkers are off in opposite directions. If the errors are random, the error will typically be smaller, though.
However, this isn't the Hanna Checkers' worst-case scenario. The fixed error terms (0.02ppm & 0.25ppm) will make it really messy when you have low nutrient levels. If we had 1.0ppm NO₃ and 0.05ppm PO₄ (true molar ratio ≈ 31:1), the readings could produce much larger errors: anything from ≈ 15:1 to ≈ 68:1 or so.

All that work, just to say: You're right, Dan. At mid-range levels we get a ballpark figure. At low nutrient levels, the checkers are basically very expensive random number generators.