Looking for thoughts on organic carbon dosing and nitrate

ReefGeezer

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I'm of the opinion that it is not diversity in and of itself that is good. I think it is having all the needed organisms in place to maintain nutrients ad provide food. It is a pretty diverse group though. This can be difficult because Nature may fill any void we leave with organisms that throws everything out of balance.

What I think I know about bacteria:
1. Some Heterotrophic Bacteria that are potentially encouraged by carbon dosing are always present in the tank, but limited by low levels of available carbon in the water column;
2. Supplying a carbon source addresses that limitation, allows the bacteria to propagate, and impacts N and, to a lessor extent, P levels;
3. Some strains of heterotrophic bacteria attain their carbon, N, & P requirements via digestion of organic compounds and don't need available carbon in the water column;
4. Adding a carbon source does not affect the function of the Heterotrophic Bacteria that fulfills its needs via digestion;
5. All the above bacteria are pervasive. They propagate when conditions meet their needs; and
6. Once a certain strain of bacteria becomes established, it becomes hard for other strains requiring the same conditions to get established.

I have always assumed that different sources of carbon might encourage different strains of bacteria.

What I think I know about heterotrophic bacterial diversity:
1. Bacterial diversity becomes limited as certain strains become established;
2. While pervasive, some strains of bacteria, particularly the ones we don't want, can establish themselves faster than others that have the same requirements;
3. Bacteria that we don't want are likely to become established when we leave it up to nature to decide;
4. Adding bacteria from a bottle or seeding it with small amounts of live rock in hopes of replacing established undesirable bacteria is not likely to produce a good outcome;
5. The optimal method of establishing the heterotrophic bacterial population and density we desire is to establish it on substrates outside the tank, introduce the substrate to the tank, and ensure its needs are met going forward.
6. Where N & P are available, a carbon source can be added to: A) Reduce N & P if desired; and B) Provide a bacteria food source in the water column.

What I think about diversity in general:
1. Bacteria and more complex organisms play an important role in nutrient processing and also serve as part of the food web;
2. Coralline algae and other biofilms, and the more complex organisms that cover the substrate discourage pest microalgae and bacterial pests just by occupying the real estate; and
3. Diversity of more complex organisms can be discouraged if pest microalgae and undesirable bacteria get a foothold on the substrate first.
 

Pntbll687

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It is frequently claimed that it takes a long time (sometimes weeks) for organic carbon dosing to reduce nitrate.

Do folks believe that is true, and if it is, why would it be true?

Are most folks just starting to dose too slowly?

Bacterial number increase is sometimes cited as a reason, but why would it take that long?

If bacterial numbers increase is the reason, then where is the organic carbon going in the meantime? Accumulating? Being used somehow in a way that does not consume nitrate? What way is that?

Any thoughts are appreciated.
I think part of the reason for the "lag" in time from when carbon dosing is started to when people see reduction is the "start too light" advice that is given across the hobby.

Reefers start with 1ml and work up, but they actually need a dose of 20-30ml to see a reduction in nitrates (depending on tank size of course). If someone is dosing 1ml a day and increasing 1ml a week, it could be months before they reach the dose that is actually required.

I think the "bacterial increase" is cited but is a result of my first observation. You would think that dosing 1ml a day, but needing 20ml (for argument's sake), would take 20 days to accumulate in the system and see reduction, but the 1ml dose is being consumed by bacteria, but isn't enough to influence the population in any meaningful way.

Now, I understand the "start too light" mentality, because a serious bacteria bloom could consume oxygen and kill fish.

I do think if people had more of an idea of what is needed, they could start with a dose closer to where they actually need to be, and see results in a shorter amount of time.
 

Dan_P

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I know that you did a long enough term vinegar dosing study in your tank that you calculated the ratio of acetic acid to nitrate reduction on a molar basis.
@Lasse has enough recent data in his system of dosing (multiple different amounts) of ethanol up through his sand bed while simultaneously tracking nitrate that the same calculation can be done approximately for his setup. There is no particular reason to think that a comparison between these two situations would yield similar numbers. But we should run the numbers and check anyway. Might be educational. My sense without calculation is that Lasse's setup gives an unusually high bang for the buck in terms of nitrate decrease per carbon dosed.
Since I dosed acetic acid and @Lasse dosed ethanol, we cannot assume the ratios will be the same. We do make that assumption when converting one to the other for dosing purposes, but we are asking a different question. Lasse might have to dose vinegar to have truly comparable data. In fact that might be the best data to check our assumptions.
 

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My carbon dosing is not aimed to "fuel" aerobic heterotopic bacteria growth - it is aimed to give anaerobic heterotopic bacteria that use NO3 as electron acceptor (in the absence of oxygen as electron acceptor and hydrogen as donator) a useful electron donator. Many studies around classic denitrification have shown that ethanol (C₂H₆O) is best suited for this. Hence I dose in the proximity of an anaerobic environment (below my DSB)

Sincerely Lasse
 
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Randy Holmes-Farley

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My carbon dosing is not aimed to "fuel" aerobic heterotopic bacteria growth - it is aimed to give anaerobic heterotopic bacteria that use NO3 as electron acceptor (in the absence of oxygen as electron acceptor)

How do you influence where it goes and what happens to it?
 

Dan_P

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My carbon dosing is not aimed to "fuel" aerobic heterotopic bacteria growth - it is aimed to give anaerobic heterotopic bacteria that use NO3 as electron acceptor (in the absence of oxygen as electron acceptor)
How are you “aiming” the dose to favor one over the other?
 

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If heterotrophic bacteria are the main beneficiary of OC, then they don't use up no3 and po4 directly. They consume things that already up took some some sort of N and P which is baked in to the current no3 and po4 numbers. Those things need a while to multiply and use up more to see a drop. This is explanation makes the most sense for the lag to me.
 

ReefGeezer

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If heterotrophic bacteria are the main beneficiary of OC, then they don't use up no3 and po4 directly. They consume things that already up took some some sort of N and P which is baked in to the current no3 and po4 numbers. Those things need a while to multiply and use up more to see a drop. This is explanation makes the most sense for the lag to me.
This has always been a question in my mind... Does the bacteria promoted by adding a carbon source uptake the carbon and NO3 and PO4 directly, or does some mechanism combine the Carbon with the NO3 & PO4 to form an organic compound that is then consumed by the bacteria? In new tanks or tanks that are new to carbon dosing, the development of the mechanism might explain the need to ramp up more slowly.
 
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Randy Holmes-Farley

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This has always been a question in my mind... Does the bacteria promoted by adding a carbon source uptake the carbon and NO3 and PO4 directly, or does some mechanism combine the Carbon with the NO3 & PO4 to form an organic compound that is then consumed by the bacteria? In new tanks or tanks that are new to carbon dosing, the development of the mechanism might explain the need to ramp up more slowly.

Such a combining mechanism would only happen inside an organism, which then makes it a sort of chicken vs egg question.
 

Lasse

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1678740379346.png

This is my system as a princip. Water and DOC is pressed down into the plenum below the sand bed. In this plenum - there is a lot of sediment . Some DOC will be used by bacteria that use the oxygen in the incoming water. The water is going up in the gravel and sooner or later there is no more oxygen. The environment will be anaerobic and bacteria start to use NO3 as electron acceptor instead for oxygen and use the DOC (not consumed by aerobic bacteria in the first step) as electron donor. The plenum is full of organic matter that will be broken down by bacteria using oxygen as long as the oxygen in the incoming water last. The DOC speed up the process here. The trick is to balance the flow of oxygen rich water and DOC addition so it will be DOC left that can serve as electron donor in the denitrification process. Normally - you need a low flow if you want to use small amount of DOC but in my case - I can run it with a rather high flow and I think that is jus the amount of organic sediment in the plenum that help me with the oxygen consumption.

When you dose DOC in open water - it will be used by aerobic bacteria as growth media and the uptake of NO3 is rather small (and concur with NH4 uptake) The system will take up PO4 too. My system is designed to only take away NO3 as denitrification (it will be converted into N2 gas). The net uptake of PO4 is more likely negative - it means that the system probably leak PO4. I deal with PO4 with help of GFO

For the moment - my redox in the plenum/sediment is positive around 300 mV. It means that the process in the plenum probably use oxygen and that the denitrification (anaerobic - not use oxygen) happens somewhere in the sand bed. The test I´m going to do in the future is to lower the flow and see if I can lower my doc dosing too - but still balance around 1-2 mg/L NO3

Sincerely Lasse
 
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This has always been a question in my mind... Does the bacteria promoted by adding a carbon source uptake the carbon and NO3 and PO4 directly, or does some mechanism combine the Carbon with the NO3 & PO4 to form an organic compound that is then consumed by the bacteria? In new tanks or tanks that are new to carbon dosing, the development of the mechanism might explain the need to ramp up more slowly.
Theoretically the assimilation of inorganic nutrients by the bacteria is already consider a organic nutrient. this is the basics of protein skimmer’s as they can not remove inorganic nutrients although once they are assimilated by the bacteria and become organic they can effectively be exported via the skimmer.
 
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sixty_reefer

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Such a combining mechanism would only happen inside an organism, which then makes it a sort of chicken vs egg question.
Inside some heterotrophic organisms this process is often made by bacteria also.
 

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This whole thread assumes organic carbon was the limiting nutrient for the bacterial bloom. (Mod edit)

To answer the original question. It takes time because you first have to increase respiration (sediment) high enough to cause a shift from aerobic to anaerobic. When that happens N will exist as ammonia and not nitrate, not only that but there while be a whole breakfast buffet of nutrients and trace elements available to the main water column from the sediment, N, P, Fe....
Now that there is no limiting nutrient in the water column, bacteria are free to do what they want.

After years of following threads it seems that the more surface area you had the quicker the response you saw in nitrate reduction. So gravel free aquariums usually required much more carbon to get a reduction than an aquarium with a sandbed.

Yeah, I have observed similar.
 
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Randy Holmes-Farley

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The previous post brings up several unknowns that would be nice to know:

1. How much of the dissolved organic dosed is used by bacteria, and how much by other organisms such as corals and sponges.

2. How much of the dosed organic is used in denitrification to produce N2 from nitrate, and how much by aerobic metabolism by O2, which only uses nitrate as the number of bacteria grow.

3. Whether the presence and amount of rocks and sand make an important difference in 1 and 2.
 

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It should read 'bacterial bloom', not algae boom in the previous post. Can't edit it.

1. How much of the dissolved organic dosed is used by bacteria, and how much by other organisms such as corals and sponges.
I remember trying sucrose and it resulting in a browning nature of sps. Glucose on the other hand would cause a lightening of sps.
It does cause a change, but i'm not sure how you would determine cause.

2. How much of the dosed organic is used in denitrification to produce N2 from nitrate, and how much by aerobic metabolism by O2, which only uses nitrate as the number of bacteria grow.
I say little is used in denitrification. My limited understanding is it tends to be more a bottom up rather than a top down process with carbon, RE Lasse model.

3. Whether the presence and amount of rocks and sand make an important difference in 1 and 2.
I'd say a whole lot. sediment (rock, sand..) is going to out compete free floating in the water column. Generally something will be limiting in the water column.

I think the cyano blooms that often happen is an important observation as well. In the shallow saltwater bays on the east coast of Australia, these benthic cyano blooms almost always happen as a result of an increase in sediment respiration. The only difference is the respiration increase is due to temperature rising during spring. Temperature, organic carbon... same result.
 
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Lasse

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2. How much of the dosed organic is used in denitrification to produce N2 from nitrate, and how much by aerobic metabolism by O2, which only uses nitrate as the number of bacteria grow.
I do not think you can do a general quantification of this.

IMO - Its differ from system to system. In that place where the denitrification should take place - DOC or POC (Particulate Organic Carbon) must be available for the aerobic heterotrophs to form such a large biomass that oxygen becomes the limiting factor. When the oxygen runs out, the facultative aerobes are forced to switch to NO3 as an electron acceptor (instead of oxygen). Remaining DOC (in my case ethanol) will then act as an electron donor in the citric acid cycle. In open systems, quite a lot of DOC is required to create small anaerobic pockets - but these need to have a water turnover as well. In my case, it becomes more controllable - the oxygen-free conditions are concentrated where I want them. In principle, first so much DOC/POC is used that the area becomes oxygen-free (due to growing bacterial mass), then there must be some DOC available to function for the anaerobic metabolism that uses NO3 as an electron acceptor.

Sincerely Lasse
 
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Max93

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Randy it took me a whole month and half of vodka dosing no results. I then switched to NOPOX and it dropped from 30 to now 7.7 as of yesterday within 3 weeks. I think you need different carbon sources for all the different bacteria in order for carbon dosing to work efficiently.

starting:

nitrates at 30
Po4 at .20

today:

nitrates 7.7
Po4 at .04
 

cvicente

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The thing with live vs dry that most do not understand is that the live already has the rock coated in things so that dinos cannot get a foothold.. even if it is just surface/film/matting bacteria.

There are many inverts and things on live rock that can be sensitive to the higher nitrate levels that people like to run. Mini brittle stars, pods, worms, etc. can all die back with no3 gets much over 10, IMO. Higher po4 plays a role in this too. Coralline can calcify and spread much faster with lower residual no3 and po4 levels.

This is a population game, not a diversity game. Even one type of matting/film bacteria that covered rocks already can keep dinos at bay whereas a few sweet rocks from the ocean will struggle to seed the rest of the tank fast enough.

There are many build thread on here with tanks full of dry rock and also a seed pack from the ocean. The ocean rock is beautiful and the dry rock is covered in nuisance algae and dinos still.

I just started up a smaller tank for Z&P. I grabbed some rock out of one of my tubs that has been kept in saltwater and mostly in the dark. I had a dino phase for about 3-4 days and it is gone now - this was pretty common in nearly every tank before dry/dead rock came about. While this rock is not from the ocean, it still has some bacteria on it and even some critters - saw a few worms and pods crawling around. The coralline and sponge will quickly come back too. I love how people either forgot, or never knew, that massive dino outbreaks were not common when people used real live rock... but I guess that is not in the BRS videos. Click on the $1000 tank thread in my signature and watch a year of growth and progress with no dino issues... again, not any dead/dry rock in there. Neither of these tanks had any detectable no3 and po4.

For me, this all comes down to expectations and definitions and why many think this is so hard. Diversity to me is not only things that we cannot see, but things that we can. I want my snails, starfish, pods, worms, etc. to be able to multiply. Some think of diversity as just two different kinds of bacteria that come in a bottle or sprayed dry on a rock. To each their own, but nobodies definition of diversity can outpopulate hair, dinos and cyano on dry rock fast enough.

I would argue that epoxy painted concrete will never be live rock. The microfauna need the porous structure to help them reproduce and survive, or at least I have always heard that and also believe it to be true. Also hard to buffer phosphate and have anoxic bacteria to turn no3 into N gas on surface epoxy.

For re-seeding, many tanks need this. If you used interceptor for bugs, it likely killed back your starfish. Levamisole any beneficial planaria. Algaecide kill your surface algae or antibiotic killed surface bacteria and some asternia are now dead. High no3 could kill other things. A pack from IPSF or a new piece of rock or two can gets most of these back.
Personal communication from Dr. Forest Rowher:

Dear Carlos,
Thanks for the inquiry. DOC versus oxygen is pretty complicated, particularly because DOC is so hard to measure.
1) Excess (1-5 micromolar) dissolved organic carbon (DOC), coupled with declines in oxygen concentrations, is the primary cause of coral reef decline.
2) Excess DOC is countered by adding more oxygen. This is common in aquarium systems.
3) It is possible to use dissolved organic carbon plus oxygen to speed up remineralization of nitrogenous compounds. You need the organic carbon to stimulate the denitrifying communities. The oxygen keeps the heterotrophic bacteria from growing out of control and killing the animals.
4) Our experiments showed that DOC, not nutrients, kill corals via microbial activity (that's why we can block it with antibiotics). This is what is happening on coral reefs. Aquariums are different because various nitrogen compounds accumulate, which doesn't happen on coral reefs until things are really bad.
5) Pulses of DOC are probably fine to help stimulate denitrification in aquariums. Just make sure to keep the oxygen concentrations up.
6) We've actually been testing how to increase oxygen & limit DOC in Puerto Rico:)
Sincerely,
Forest

Second reply:

Dear Carlos,
1) Yes, the Arks project in Vieques is a direct test of DOC versus oxygen. Basically, by moving the coral & associated invertebrates higher into the water column, we observe that the microbial community behaves more like a pristine reef. As is usual with DOC and oxygen, it is a combination of increasing the oxygen from the surrounding water & decreasing the DOC produced by the macroalgae.
2) Yes, please feel free to share the comments with aquarists that are interested.
Sincerely,
Forest
 
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Randy Holmes-Farley

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This is my system as a princip. Water and DOC is pressed down into the plenum below the sand bed. In this plenum - there is a lot of sediment . Some DOC will be used by bacteria that use the oxygen in the incoming water. The water is going up in the gravel and sooner or later there is no more oxygen. The environment will be anaerobic and bacteria start to use NO3 as electron acceptor instead for oxygen and use the DOC (not consumed by aerobic bacteria in the first step) as electron donor. The plenum is full of organic matter that will be broken down by bacteria using oxygen as long as the oxygen in the incoming water last. The DOC speed up the process here. The trick is to balance the flow of oxygen rich water and DOC addition so it will be DOC left that can serve as electron donor in the denitrification process. Normally - you need a low flow if you want to use small amount of DOC but in my case - I can run it with a rather high flow and I think that is jus the amount of organic sediment in the plenum that help me with the oxygen consumption.

When you dose DOC in open water - it will be used by aerobic bacteria as growth media and the uptake of NO3 is rather small (and concur with NH4 uptake) The system will take up PO4 too. My system is designed to only take away NO3 as denitrification (it will be converted into N2 gas). The net uptake of PO4 is more likely negative - it means that the system probably leak PO4. I deal with PO4 with help of GFO

For the moment - my redox in the plenum/sediment is positive around 300 mV. It means that the process in the plenum probably use oxygen and that the denitrification (anaerobic - not use oxygen) happens somewhere in the sand bed. The test I´m going to do in the future is to lower the flow and see if I can lower my doc dosing too - but still balance around 1-2 mg/L NO3

Sincerely Lasse

Thanks, Lasse.
 
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