Total Organic Carbon (TOC) Survey

[Dan_P]

I collated total organic carbon (TOC) analyses from Feldman’s articles and R2R posts of N-DOC results. This collection of data serves as background information for my work and I thought you might be interested in it as well. I look forwards to future posts of N-DOC results.

In the first plot, the dashed line is the average of the TOC values taken from Table 1 in Feldman’s first article on TOC https://www.advancedaquarist.com/2008/8/aafeature3. I did not include the 10 ppm value from Florida Bay, Florida. The blue circles are the individual values. The red squares are the aquarium TOC values at 20-24 hours after feeding found in Feldman’s second article https://www.advancedaquarist.com/2008/9/aafeature2. The purple diamonds are the N-DOC TOC values reported by forum members. These values are substantially higher than the aquarium TOC’s measured by Feldman. I have no idea if that is good, bad, or who cares.

In the second plot I compare the measured total nitrogen value to the TOC value. I found the lack of a strong correlation interesting, maybe surprising, though much more more data is needed before anything definite can be concluded. For Redfield Ratio fans, this might be very interesting.

 

[Sallstrom]

@Dan_P would you like more data? We've three more reef tanks at work where we've tested N-DOC 2-3 times each.

 

[rkpetersen]

I've tried the Triton NDOC test on one of my tanks.
I was sure this tank was low in dissolved organics, and that proved to be the case.

TOC 1.27 mg/l
TNb 0.57 mg/l

In that Feldman article, the highest TOC he recorded from natural water was 1.67 ppm (ignoring two outliers.)
It's not surprising that most aquaria have higher levels than that. It accumulates, like nitrate and phosphate.
I wouldn't say a higher level is 'good', but how 'bad' it is is probably subject to many variables and unknown overall.

 

[Dan_P]

@Dan_P would you like more data? We've three more reef tanks at work where we've tested N-DOC 2-3 times each.

Yes @Sallstrom, more data would wonderful. Thank you. Dan

 

[Sallstrom]

More data!

 

[Dan_P]

More data!

This is fantastic @Sallstrom. Thank you. I will add these to the database and post updated plots. Dan

 

[Dan_P]

Thanks to @Sallstrom data, the number of data points in my survey has doubled. The updated charts continue to show higher TOC levels than Feldman’s data. The second plot of total nitrogen vs total organic carbon continues to interesting, i.e., seems to be no correlation between nitrogen and carbon AND most of the nitrogen levels are similar. Maybe removing the nitrate nitrogen from the total nitrogen would show a trend with increasing total organic carbon.

 

[Dan_P]

My turn to contribute data. By the way the Hanna alkalinity of the sample was 3 meq/L and nitrate around 0.3 ppm or about .07 ppm N.

 

[taricha]

Thanks to @Sallstrom data, the number of data points in my survey has doubled. The updated charts continue to show higher TOC levels than Feldman’s data.

This is excellent.
Can you link Feldman's results?
I'm sure if the discrepancy between Feldman and Triton were easily explained, you'd have said so. But do you think it's more likely the samples he tested were actually all different than the Triton samples or that we're seeing a methodology effect?
We're getting close to having enough data now to start looking at tank specifics and say what's "high" and "low" TOC and what in the tank histories might contribute.
On the high end, Lasse I know adds "Chaeto Juice" which seems relevant (mitigating factor: oxidator?)
On the low end, You skim what I would consider very large volumes of wet skimmate daily.
Curious about husbandry effects that we can correlate to high or low TOC.

 

[Dan_P]

This is excellent.
Can you link Feldman's results?
I'm sure if the discrepancy between Feldman and Triton were easily explained, you'd have said so. But do you think it's more likely the samples he tested were actually all different than the Triton samples or that we're seeing a methodology effect?
We're getting close to having enough data now to start looking at tank specifics and say what's "high" and "low" TOC and what in the tank histories might contribute.
On the high end, Lasse I know adds "Chaeto Juice" which seems relevant (mitigating factor: oxidator?)
On the low end, You skim what I would consider very large volumes of wet skimmate daily.
Curious about husbandry effects that we can correlate to high or low TOC.

Enjoy the reading!
https://www.advancedaquarist.com/2008/8/aafeature3
https://www.advancedaquarist.com/2008/9/aafeature2

In addition to the question “why the differences in TOC levels”, why do the total nitrogen levels appear to center around 1.5 ppm? Is the collection of molecules that make up your system’s TOC roughly the same as those in my system? Assuming very useful organic compounds are consumed rapidly, say within minutes to hours, do the TOC measurements reflect mostly refractory material that no organism consumes?

 

[Cory]

Curious what do the results say?

Would be cool to see how the tanks look with their numbers. I wonder if their is a correlation.

 

[Randy Holmes-Farley Verified Community Expert]

How are home reefers distinguishing dissolved from particulate organic matter?

 

[rkpetersen]

How are home reefers distinguishing dissolved from particulate organic matter?

I don't think there is a way, currently.
I wonder if Triton filters water samples with a 0.2 micron filter first to remove POM.
I would guess that they don't, and that the measurements reflect both DOM and POM.

 

[Randy Holmes-Farley Verified Community Expert]

I don't think there is a way, currently.
I wonder if Triton filters water samples with a 0.2 micron filter first to remove POM.
I would guess that they don't, and that the measurements reflect both DOM and POM.

Which may be a reason that numbers cannot be compared to literature data where there is such a distinction.

 

[Dan_P]

How are home reefers distinguishing dissolved from particulate organic matter?

What’s on your mind? Are we mixing things up already?

 

[Dan_P]

Here is another contribution to the TOC survey. I conclude nothing from this sparse data collection. I share it for your enjoyment.

Pre- and Post GAC Change N-DOC Results