Carbon Dosing A Model Aquarium

[Dan_P]

Couple questions come to mind...
If I'm interpreting this correctly..
The ethanol is clearly more effective at lowering residual nutrients(?). But, the acetate is said to be taken up by many organisms(main benefit) - not just no3/po4 consuming bacteria. So is it possible that, in a running reef tank, the results might be more equal. Or is the path for the acetate just slower and the relationship with the other organisms is irrelevant to the nutrient decrease?

Yes, ethanol is more effective in this experiment.

I think if acetate were taken up by a larger variety of organisms than what is in the water, there would be greater variety of C:N demand which might turn out to be a lower average C:N ratio, that is more nitrate taken up per vinegar dose. The situation could also be that the average C:N ratio of the aquarium is higher, meaning less nitrate taken up per dose. I don’t have a good feeling for what nitrate reduction per dose is being obtained by folks.

There are several potential reasons for a slow nitrate reduction process that do not involve acetate consumption by organisms other than bacteria. I hope to test some of these.

 

[Randy Holmes-Farley Verified Community Expert]

If I'm interpreting this correctly..
The ethanol is clearly more effective at lowering residual nutrients(?).

I would not make that claim in that way unless it is stated as

The ethanol is clearly more effective at lowering residual nutrients on a per molecule basis.

Reason being I’m not sure any reefer cares about that when using either one. Few reefers even know how to compare them on a per molecule basis even after using them.

Dans’s data shows they are much more similar when compared on an O2 consumed basis (acetate is ethanol after partial oxidation) which maybe is something people care about.

Most likely, all they care about is whether nutrients are reduced at a reasonable cost and bother before something else bad happens, such as cyano. This experiment to me says they are quite similar in ability to reduce nutrients and folks should use what works best. :)

 

[Reefering1]

But that difference between the 2 is about 8x, correct?

 

[Marc Pardon]

Very nice experiment. Thanx for sharing. Any idea what the ammonia concentration is in your measured water? Could this be only decreasing with the lower amounts of carbon dosing (<0,5)? Another question would be : could we make nitrate reduction in reef tanks more efficiently with lower carbon doses with a combination of bacteria supplements? Never finded use for this supplement but thinking about de results here it was my first initial thought that came to mind .....Most people are using the carbon source in a free floating form and not in a dedicated place like a DSB etc ....

 

[Dan_P]

Very nice experiment. Thanx for sharing. Any idea what the ammonia concentration is in your measured water? Could this be only decreasing with the lower amounts of carbon dosing (<0,5)? Another question would be : could we make nitrate reduction in reef tanks more efficiently with lower carbon doses with a combination of bacteria supplements? Never finded use for this supplement but thinking about de results here it was my first initial thought that came to mind .....Most people are using the carbon source in a free floating form and not in a dedicated place like a DSB etc ....

Thanks!

There is undetectable ammonia in the aquarium water I use, but I believe there can be a tiny amount. A future investigation will study how the presence of ammonia affects nitrate consumption during organic carbon dosing.

Adding bottled bacteria is unlikely to have any effect because there should already be a sufficient number and type of bacteria in an aquarium both in the water and covering the surfaces to consume nitrate.

Even though the carbon source is dosed to and consumed in the water, it also makes it way to the surfaces and sand bed to be consumed. I have an experiment planned to measure the rate of nitrate consumption in the water and by a biofilm covered surface to get a feel for where in the aquarium nitrate consumption occurs.

 

[Marc Pardon]

@Dan_P : thanx for the answers. Make sense. Very nice experiments ahead. That would gave us more answers and indications ;)

 

[Randy Holmes-Farley Verified Community Expert]

But that difference between the 2 is about 8x, correct?

You mean comparing typical vinegar weight concentrations of acetic acid to typical vodka weight concentrations of ethanol, yes that is 8x. That same comparison is 10.4 x on a per molecule basis.

 

[taricha]

What is interesting about these results and maybe just a coincidence is that phosphate consumption for ethanol dosing is higher than vinegar dosing by approximately the same amount as the amount oxygen needed to fully oxidize ethanol compared to acetic acid (1.5 x).

once upon a time we mentioned that vinegar contains PO4. I think we decided about 1ppm? If so, I think that's small enough to be negligible and that input can't help account for PO4 difference between vinegar and ethanol. But I thought I'd mention it and check for easy answers.

I am now using the low range nitrate test for better resolution and should be better prepared to sort out signal from the noise.

...the dedication.

The water in the ethanol treatment became hazy with the heavier dose and the vinegar dose became hazy later on. After decanting the medium, a biofilm could be seen in both aquaria, though the biofilm in the ethanol treatment appeared heavier.

In cases where I dosed enough ethanol or vodka to containers outside aquaria, I saw more films/solids with ethanol than vinegar. But that was mostly just an impression, not something I collected data on.
In an aquarium, I couldn't generate a significant detectable difference in films, cloudiness, or skimmed material between vodka and vinegar.

 

[Dan_P]

once upon a time we mentioned that vinegar contains PO4. I think we decided about 1ppm? If so, I think that's small enough to be negligible and that input can't help account for PO4 difference between vinegar and ethanol. But I thought I'd mention it and check for easy answers.


...the dedication.



In cases where I dosed enough ethanol or vodka to containers outside aquaria, I saw more films/solids with ethanol than vinegar. But that was mostly just an impression, not something I collected data on.
In an aquarium, I couldn't generate a significant detectable difference in films, cloudiness, or skimmed material between vodka and vinegar.

Thanks for this. There seems to be reasonable agreement between the results from the model system and real life observations. I am finding scaling down further though is giving me a smaller or no consumption rate. I don’t have the bandwidth to study this and decided to side step it by working at 0.5 liters and above for now. My BOD bottles are about 100 mL and I may have to figure this out when I start studying oxygen consumption.

By the way, the dilution rate for vinegar in this study is about 1/3800. The residual phosphate in vinegar would not make a significant contribution.

 

[Dionysos]

Hello,
That ethanol is more effective is obvious if we compare the energy values of ethanol and vinegar at their usual concentrations.
Don't you think that a good recipe should take into account: the level of elemental carbon, the energy value of the composition, the bioavailability of the type of carbon (saccharose seems a nonsense). And that the dosage should depend on the level of pollution (more nitrates and phosphates allow more carbon to be assimilated).
This is the approach discussed here: https://reeflexion.fr/doser-carbone-aquariophilie-recifale/

 

[Randy Holmes-Farley Verified Community Expert]

Hello,
That ethanol is more effective is obvious if we compare the energy values of ethanol and vinegar at their usual concentrations.
Don't you think that a good recipe should take into account: the level of elemental carbon, the energy value of the composition, the bioavailability of the type of carbon (saccharose seems a nonsense). And that the dosage should depend on the level of pollution (more nitrates and phosphates allow more carbon to be assimilated).
This is the approach discussed here: https://reeflexion.fr/doser-carbone-aquariophilie-recifale/

I'm not sure I agree with some of the things written in that link, but since it is not in English, translation issues using google translate might be the problem.

Since every reef tank titrates the dose to get the desired effect, the small difference in the per molecule effects of ethanol vs acetic acid do not seem to me to be necessary to focus on. General recipe starting dose guidelines take the concentrations into account, but not the minor corrections for energy.

https://www.reef2reef.com/threads/new-vodka-and-vinegar-dosing-charts.1024056/
I do some detailed analyses of the energy available from acetate and ethanol, and there are actually different ways to approach that comparison with somewhat different answers. For example, the relative energy from burning these molecules with O2 (that's what you'd see in a table most of the time), or the actual ATP energy created (which involves all of the limitations biological systems have in oxidizing molecules for energy).

https://www.reef2reef.com/threads/reef-chemistry-question-of-the-day.172883/

 

[Dan_P]

Hello,
That ethanol is more effective is obvious if we compare the energy values of ethanol and vinegar at their usual concentrations.
Don't you think that a good recipe should take into account: the level of elemental carbon, the energy value of the composition, the bioavailability of the type of carbon (saccharose seems a nonsense). And that the dosage should depend on the level of pollution (more nitrates and phosphates allow more carbon to be assimilated).
This is the approach discussed here: https://reeflexion.fr/doser-carbone-aquariophilie-recifale/

What you are describing is happening in the aquaculture industry. To minimize nitrogen waste, especially ammonia, the amount of excess nitrogen in the feed is calculated and the appropriate amount of organic carbon is added to the system to create bacteria biomass which is either removed or serves as food for the organism being raised, such as shrimp. There is nothing stopping aquarists trying this proactive approach.

A good recipe as you describe is possible. I think we aquarists find the empirical approach of adding carbon until we obtain the nitrate reduction we want works also works.

 

[Dionysos]

Thank you for your comments.

Ok, the energy differences can be compensated by the concentration of the carbon source. And finally, these approximations do not matter if the objective is achieved.

So, the bioavailability of the carbon source should be the essential criterion for choice. For example acetate instead of ethanol, or glucose instead of saccharose, no ?

 

[Dan_P]

Thank you for your comments.

Ok, the energy differences can be compensated by the concentration of the carbon source. And finally, these approximations do not matter if the objective is achieved.

So, the bioavailability of the carbon source should be the essential criterion for choice. For example acetate instead of ethanol, or glucose instead of saccharose, no ?

I would make a guess that all bacteria will consume glucose, maybe some bacteria can’t use disaccharides, like sucrose, many can use acetate and ethanol might be the least widely used carbon source for bacteria. I not sure for the average aquarium the difference matters, but worth keeping this idea it mind.

What might be important is the rate of growth, and therefore, oxygen consumption rate differences for various carbon sources.

 

[Dionysos]

Yes, and the rate of O2 consumption is also dependent on bioavailability, the ease of assimilation.

Another aspect: research has highlighted the impact of certain sugars on the development of pathogens such as Vibrio. It seems to me that at high concentrations dextrose would be less critical than glucose. Both available in the natural environment. A track rarely discussed in reef aquariums.

 

[Randy Holmes-Farley Verified Community Expert]

Yes, and the rate of O2 consumption is also dependent on bioavailability, the ease of assimilation.

Another aspect: research has highlighted the impact of certain sugars on the development of pathogens such as Vibrio. It seems to me that at high concentrations dextrose would be less critical than glucose. Both available in the natural environment. A track rarely discussed in reef aquariums.

I do not recommend dosing any sugars, and while the VSV recipe has been around for years, I see almost no reef2reef members mentioning using sugars as all or part of organic dosing.

 

[Dionysos]

How can this be explained, why not recommend it, since certain sugars are assimilated by coral mucus bacteria in the natural environment?

 

[Randy Holmes-Farley Verified Community Expert]

How can this be explained, why not recommend it, since certain sugars are assimilated by coral mucus bacteria in the natural environment?

You are asking why I do not recommend sugars, but do recommend ethanol and acetic acid?

My one experiment with dosed sucrose rapidly ended in corals browning up, probably from excess zoox.

I’ve seen more folks report problems with dosing of sugars.

There are studies like this that show problems:

https://www.int-res.com/articles/meps2005/294/m294p173.pdf

 

[Dan_P]

You are asking why I do not recommend sugars, but do recommend ethanol and acetic acid?

My one experiment with dosed sucrose rapidly ended in corals browning up, probably from excess zoox.

I’ve seen more folks report problems with dosing of sugars.

There are studies like this that show problems:

https://www.int-res.com/articles/meps2005/294/m294p173.pdf

If the aquarium does not contain hard coral, is your concern about sugars reduced or eliminated?

 

[Randy Holmes-Farley Verified Community Expert]

If the aquarium does not contain hard coral, is your concern about sugars reduced or eliminated?

Not sure. :)