Reflects before you begin dosing carbohydrates

[Belgian Anthias]

The way it is done is irrelevant?

The way it is done is irrelevant?

I don't understand what you are saying here. As long as the nitrate level is acceptable, whether the level is maintained by denitrification or by carbon dosing seems irrelevant. Tuning the dose (the carbon input) to match the nitrate imported via food requires some trial and error, but doesn't seem to be a significant problem.

The way it is done is irrelevant?

When nitrate is denitrified NO3-N is removed from the system and the carrying capacity, the ability of the system to remove ammonia, of the system is maintained at all times even when denitrification is interrupted or stopped for a period of time.

When nitrate must be assimilated first all NH4-N must be assimilated into biomass, than NO3-N may be used. As there is insufficient ammonia availability for nitrification no or little nitrate is produced and the nitrifying capacity is drastically reduced or stopped. The carrying capacity of the system, the ability to remove ammonia, may depend largely or completely on dosing. When dosing is interrupted or stopped the system needs time to reinstall sufficient autotrophic carrying capacity bringing the system in an unbalanced and possible very dangerous situation.
Most nitrogen is not removed but taken into a not ending cycle within the closed environment of the aquarium.

Leaves the other pro's and con's of both complete different applications.

 

[Belgian Anthias]

Skimmer

Skimmer

You've posted that paper before. I still don't understand the relevance. What are you trying to say?

As a lot of users think that a skimmer removes the biomass produced by carbon dosing the limited ability to remove biomass by skimmers is more than relevant.

 

[Belgian Anthias]

"What to do with the continually increasing biomass " is one of the problems to solve.

If one is able to complete the food chain one can introduce some Litopenaeus vannamei,in a refuge which will be harvested when big enough to be consumed. This way nothing is lost.:spin2:

 

[bertoni]

The way it is done is irrelevant?

That's my opinion.

When dosing is interrupted or stopped the system needs time to reinstall sufficient autotrophic carrying capacity bringing the system in an unbalanced and possible very dangerous situation.

The system might or might not require much time to recover an ammonia-processing capacity. I don't see why this is relevant. If you're worried, just back off slowly on carbon dosing. That's what I generally recommend.

I'm not sure what you mean by "unbalanced". Balanced with respect to what? I also disagree about carbon dosing being particularly dangerous. I haven't seen any evidence of that since the dosing guidelines were created.

 

[bertoni]

As a lot of users think that a skimmer removes the biomass produced by carbon dosing the limited ability to remove biomass by skimmers is more than relevant.

The paper covers the effectiveness of skimming in one set of circumstances. I am not sure how this situation applies directly to carbon dosing.

"What to do with the continually increasing biomass " is one of the problems to solve.

I see no evidence of a continually increasing biomass due to carbon dosing, nor do I understand how that could happen.

 

[Dan_P]

I see no evidence of a continually increasing biomass due to carbon dosing, nor do I understand how that could happen.

I think the notion is that the carbon being dosed induces a growing number of bacteria. To assimilate nitrogen and phosphorous, bacterial biomass must increase. If the number of bacteria aren't increasing, the uptake of nitrogen and phosphorous will not be as high. I don't have a feeling for how long a bacterium that isn't dividing exists and if it does "œjust" live, how much material it needs to just hang around.

Where things get really fuzzy for me in this discussion is the rate of biomass accumulation in an aquarium, say for every gram of food you add to the tank. First, a lot of carbon is consumed for energy needs with CO2 given off. More than 50% I believe. What isn't eaten by the fish is consumed by bacteria, protozoa, fungus, etc. When bacterial biomass is eaten, more than half that carbon goes to CO2. When whatever ate the bacterium is eaten, half of that carbon goes to CO2. Carbon, and biomass, leave the aquarium as you move up the food chain. Do we know at what point that it accumulates at an unhealthy level? Is that point different for every system?

Nitrogen added to the aquarium by food either goes to either biomass or waste (N2, NH3, NO3, slowly metabolized organic nitrogen compounds). Changing the ratio of C:N in the food or by carbon dosing means shifting wasted nitrogen to biomass nitrogen. But at what point does this biomass derived from food need to be harvested. I suppose if bacterial biomass grows quicker than predation reduces it, you grow a visible slime. Or if the nitrogen level becomes too low to support a large population of bacteria that was created by carbon dosing, I guess the bacterial population declines or crashes, maybe releasing waste back into the aquarium. In either case, you would have needed to harvest bacterial biomass more aggressively. Still trying to wrap my head around what you would need to know to calculate this. I need to review the notion of bioload and see how other life forms are considered in estimating bioload limits.

Enjoying the insights.

Dan

 

[bertoni]

I think the notion is that the carbon being dosed induces a growing number of bacteria. To assimilate nitrogen and phosphorous, bacterial biomass must increase. If the number of bacteria aren’t increasing, the uptake of nitrogen and phosphorous will not be as high. I don’t have a feeling for how long a bacterium that isn’t dividing exists and if it does “just” live, how much material it needs to just hang around.

I agree that creating more net biomass is likely to consume nitrogen and phosphorus at a higher rate than other consumption patterns. That said, a lower consumption rate might be fine. Whether a tank takes an hour to consume a daily dose of vinegar or 12 hours, either way, nitrogen and phosphorus seem to be converted to a skimmable form in some tanks, from what we can see. The biomass must stop increasing at some point, or the tank would be filled (literally) with bacteria, but that does not imply that export stops, or won't be effective. For all we know, dying bacteria or their remains might be highly skimmable.

Where things get really fuzzy for me in this discussion is the rate of biomass accumulation in an aquarium, say for every gram of food you add to the tank. First, a lot of carbon is consumed for energy needs with CO2 given off. More than 50% I believe. What isn’t eaten by the fish is consumed by bacteria, protozoa, fungus, etc. When bacterial biomass is eaten, more than half that carbon goes to CO2. When whatever ate the bacterium is eaten, half of that carbon goes to CO2. Carbon, and biomass, leave the aquarium as you move up the food chain. Do we know at what point that it accumulates at an unhealthy level? Is that point different for every system?

I certainly agree that we don't know much about the rate of biomass increase in our tanks. As far as bad effects of carbon dosing, in some cases, tanks seem to suffer from bacterial slimes or even cloudy water. I don't know whether those cases truly are dangerous, or just esthetic, but I tend towards caution when giving recommendations.

Of course, some bacteria might produce problematic or even toxic compounds. In addition, increasing the total organic load in the tank might cause problems. Some tanks might have issues of this type, which is why I tend to encourage a slow increase in the carbon dose. Even so, most problems seem to be starving corals, rather than organics. We lack useful tools to be sure what's happening, though. The same issue can occur in tanks without carbon dosing, as well.

Nitrogen added to the aquarium by food either goes to either biomass or waste (N2, NH3, NO3, slowly metabolized organic nitrogen compounds). Changing the ratio of C:N in the food or by carbon dosing means shifting wasted nitrogen to biomass nitrogen. But at what point does this biomass derived from food need to be harvested.

"Harvesting" is a bit ambiguous here. If you mean direct harvesting by the person or persons running the tank, I doubt that there's any need to do so unless the owner prefers, for example, to run with a growing slime mass and siphoning it from the system. I haven't seen any signs that active harvesting is required. I agree that some set of organisms or viruses are consuming at least some or even most of the bacteria, but I don't know how to quantify that. Direct skimming might remove some bacteria directly, for example.

I suppose if bacterial biomass grows quicker than predation reduces it, you grow a visible slime. Or if the nitrogen level becomes too low to support a large population of bacteria that was created by carbon dosing, I guess the bacterial population declines or crashes, maybe releasing waste back into the aquarium. In either case, you would have needed to harvest bacterial biomass more aggressively. Still trying to wrap my head around what you would need to know to calculate this. I need to review the notion of bioload and see how other life forms are considered in estimating bioload limits.

I agree that a visible slime is one possibility. I'm not so sure that bacterial crashes are going to be a significant danger. Bacterial populations can increase quite rapidly, generally, so I'd expect that a crash would be undetectable with hobbyist equipment. Stopping feeding seldom seems to cause issues, for example, and it's actually a step that I often recommend when dealing with various nutrient buildup or tank crash situations.

 

[Dan_P]

I agree that creating more net biomass is likely to consume nitrogen and phosphorus at a higher rate than other consumption patterns. That said, a lower consumption rate might be fine. Whether a tank takes an hour to consume a daily dose of vinegar or 12 hours, either way, nitrogen and phosphorus seem to be converted to a skimmable form in some tanks, from what we can see. The biomass must stop increasing at some point, or the tank would be filled (literally) with bacteria, but that does not imply that export stops, or won't be effective. For all we know, dying bacteria or their remains might be highly skimmable.

Isn't the notion of carbon dosing essentially growing bacteria? And if so, the rate of increase of a bacterial population depends on conditions, in this case, increasing carbon increases bacterial biomass (I wonder if one gram of carbon results in some tenths of a gram of bacteria. Sounds like too much, there is predation and export as you point out.). And you are right, we typically don't fill our aquarium with bacteria, though that would be an interesting calculation. 40 gallons of bacteria equals how much vodka. However, when the nitrogen or phosphorous is used up, I am pretty sure the larger bacterial population has few choices if any but to die or form spores. I think to move forwards at this point we need to answer the question how many bacteria are generated from a mg of NH3. I don't know off hand what a typical bacterial stoichiometric ratio of elements is but assume 5% by weight is nitrogen. That gives 20 milligrams dry weight of bacteria. Spread throughout the aquarium that amount would be invisible, yes? And if skimmable, I would guess removed or diminished in number quite easily. There must be a portion lost through predation too.

"Harvesting" is a bit ambiguous here.

I have macro algae on the brain

I agree that a visible slime is one possibility. I'm not so sure that bacterial crashes are going to be a significant danger. Bacterial populations can increase quite rapidly, generally, so I'd expect that a crash would be undetectable with hobbyist equipment. Stopping feeding seldom seems to cause issues, for example, and it's actually a step that I often recommend when dealing with various nutrient buildup or tank crash situations.

If one suddenly stops dosing carbon and there is no ammonia spike, you have not killed off or severely impacted the system's ammonia processing capability, i.e., no crash, right?

So where are we? Carbon dosing could impact autotrophs but we have little or no data to say this is a large downside. In principle, we should remove the extra bacteria we grow with carbon dosing to maximize nutrient export but this might not be totally necessary if that bacterial biomass is assimilated and locked up long term in some other biomass, e.g., the tanks population of protozoa, rotifers, amphipods, etc. Are we done here?

 

[bertoni]

Isn't the notion of carbon dosing essentially growing bacteria?

Well, that depends on what you mean... The stated goal is to export phosphorus and nitrogen from the system by consuming them from the water column, and then out of the tank via the skimmer. That process could be accomplished by growing a fairly steady bacteria population that exports nutrients via skimming byproduct and the inevitable death and replacement rate, at least in theory. So a net increase of bacterial mass might not be required. Given that some people report dosing carbon for years, it's fairly clear to me that the tank reaches a relative steady state, possibly fairly quickly. Of course, export by skimming the bacteria themselves probably happens to at least some extent. I don't know of anyone who has surveyed the change in bacterial levels in the skimmate with carbon dosing, not over a long time frame, anyway.

And if so, the rate of increase of a bacterial population depends on conditions, in this case, increasing carbon increases bacterial biomass (I wonder if one gram of carbon results in some tenths of a gram of bacteria. Sounds like too much, there is predation and export as you point out.). And you are right, we typically don't fill our aquarium with bacteria, though that would be an interesting calculation. 40 gallons of bacteria equals how much vodka. However, when the nitrogen or phosphorous is used up, I am pretty sure the larger bacterial population has few choices if any but to die or form spores. I think to move forwards at this point we need to answer the question how many bacteria are generated from a mg of NH3. I don't know off hand what a typical bacterial stoichiometric ratio of elements is but assume 5% by weight is nitrogen. That gives 20 milligrams dry weight of bacteria. Spread throughout the aquarium that amount would be invisible, yes? And if skimmable, I would guess removed or diminished in number quite easily. There must be a portion lost through predation too.

All interesting points. I personally would guess that there's a lot of mortality in the bacterial population. Viruses and other microbes are happy to kill or consume bacteria. If my memory is correct, the ocean has more viruses looking to infect bacteria than it has bacteria to infect. Our tanks might be similar.

If one suddenly stops dosing carbon and there is no ammonia spike, you have not killed off or severely impacted the system's ammonia processing capability, i.e., no crash, right?

That's possible. In addition, the ammonia-processing capacity might increase very rapidly in response to the input. At some point, we'll be arguing over wording here. The end result is the same.

So where are we? Carbon dosing could impact autotrophs but we have little or no data to say this is a large downside. In principle, we should remove the extra bacteria we grow with carbon dosing to maximize nutrient export but this might not be totally necessary if that bacterial biomass is assimilated and locked up long term in some other biomass, e.g., the tanks population of protozoa, rotifers, amphipods, etc. Are we done here?

I am sure that carbon dosing will have some impact on autotrophs. I am skeptical about the downside being significant, given the experiences reported here. I think we're done, pending data on what is happening. That data is going to be very expensive to produce, I'd guess, which is too bad. It'd be interesting to see what's happening.

 

[Dan_P]

Well, that depends on what you mean... The stated goal is to export phosphorus and nitrogen from the system by consuming them from the water column, and then out of the tank via the skimmer. That process could be accomplished by growing a fairly steady bacteria population that exports nutrients via skimming byproduct and the inevitable death and replacement rate, at least in theory. So a net increase of bacterial mass might not be required. Given that some people report dosing carbon for years, it's fairly clear to me that the tank reaches a relative steady state, possibly fairly quickly. Of course, export by skimming the bacteria themselves probably happens to at least some extent. I don't know of anyone who has surveyed the change in bacterial levels in the skimmate with carbon dosing, not over a long time frame, anyway.

This seems like a reasonable high level description. I wonder if what you are feeding by carbon dosing takes over ammonia capture and export from the ammonia oxidizers-denitrifying system.

I would wager that the steady state that you posit above is reached when the ratio of carbon added to the food nitrogen added is at the correct ratio to favor near complete assimilation with little or no waste ammonia to be oxidized to nitrate. This is Belgian Anthias' point. And when there is a reduced amount of nitrate, then maybe the denitrifying bacteria population is decreased, another Belgian Anthias point.

I have a fish only system with a lot of macro algae but periodic outbreaks of unsightly things (diatoms, cyanobacteria, dinoflagellates all ID'd under a microscope) BUT phosphates are usually undetectable and nitrates less than 0.5 ppm except for occassional unexplained short term nitrate spikes. PO4 and NO3 are poor perdictors of nuissance organism growth. So, I am wondering now based on this debate whether shifts in ammonia production-consumption might be a useful predictor, though impossible for me to measure. I might just try carbon dosing based of nitrogen input to see if the periodic nuissance growth goes away.

Dan

 

[bertoni]

I absolutely agree that it's possible that the nitrifying and denitrifying bacteria to be impacted, but I don't see any evidence that this is dangerous. At this point, there are a lot of tanks running with carbon dosing.

I'd like to know what actually happens to the organic carbon and the nitrifying-denitrifying microbes, but I don't see a reasonable way to get that information. I might be wrong, but that seems to be an expensive proposition.

 

[Belgian Anthias]

That's my opinion.

The system might or might not require much time to recover an ammonia-processing capacity. I don't see why this is relevant. If you're worried, just back off slowly on carbon dosing. That's what I generally recommend.

I'm not sure what you mean by "unbalanced". Balanced with respect to what? I also disagree about carbon dosing being particularly dangerous. I haven't seen any evidence of that since the dosing guidelines were created.

If it was that simple we would not have this discussion.
Is removing the normal nitrogen cycle which was installed and replace it by an other without risk? May be. May be not? For me it is not a good idea, the reason why I have explained.

 

[Belgian Anthias]

increasing carbon increases bacterial biomass (I wonder if one gram of carbon results in some tenths of a gram of bacteria. Sounds like too much, there is predation and export as you point out.). And you are right, we typically don't fill our aquarium with bacteria, though that would be an interesting calculation. 40 gallons of bacteria equals how much vodka. However, when the nitrogen or phosphorous is used up, I am pretty sure the larger bacterial population has few choices if any but to die or form spores. I think to move forwards at this point we need to answer the question how many bacteria are generated from a mg of NH3. I don't know off hand what a typical bacterial stoichiometric ratio of elements is but assume 5% by weight is nitrogen. That gives 20 milligrams dry weight of bacteria. Spread throughout the aquarium that amount would be invisible, yes? And if skimmable, I would guess removed or diminished in number quite easily. There must be a portion lost through predation too.

I have macro algae on the brain

So where are we? Carbon dosing could impact autotrophs but we have little or no data to say this is a large downside. In principle, we should remove the extra bacteria we grow with carbon dosing to maximize nutrient export but this might not be totally necessary if that bacterial biomass is assimilated and locked up long term in some other biomass, e.g., the tanks population of protozoa, rotifers, amphipods, etc. Are we done here?

For removing 1 gram of NH4-N by assimilation into biomass 8 grams of protein VSS must be produced. http://www.baharini.eu/baharini /doku.php?id=nl:makazi:het_water:ammonium_reductie +- 4 gram carbon is needed to remove 1 gram NH4-N. +- Half the weight of VSS is carbon. 8 grams of bacterial protein corresponds to approximately 35,2 grams of bacteria. Not included the weight of the reserves stored in vacuoles. 1 gram carbon may be responsible for +- 9 gram bacteria.
400 grams bacteria contain 300 gram water and 100 gram dry material (TSS). TSS consits of 90 gram organic material (VSS) and 10 gram minerals. http://www.baharini.eu/baharini/doku.php?id=nl:makazi:bio-chemie:bacteriën

In fact the only thing we add is the carbohydrate as the rest is provided by the system and feeding.

All approved data to prove my point is available in de Makazi Baharini wiki.

Every link in the food chain will use +- 10 % of the consumed protein and release the rest, most of it as ammonia and ureum. In the case of scrimp as an end user 90% is released back into the system the same day. Some will be used to produce energy the rest will be released when the scrimp dies. To remove something the scrimp must be harvested.

The increase in biomass I do not see as a real problem as this is easily compensated for by the feeding's.

The use of fotoautotrophic ammonia reduction is in my opinion the best way to reduce ammonia and nitrate. A problem may be that +-200 grams of algae must be harvested daily to remove 1 gram NH4-N daily ( 1ppm in a 1000l aquarium)

An other way is increasing the denitrification rate.

 

[Belgian Anthias]

I absolutely agree that it's possible that the nitrifying and denitrifying bacteria to be impacted, but I don't see any evidence that this is dangerous. At this point, there are a lot of tanks running with carbon dosing.

I'd like to know what actually happens to the organic carbon and the nitrifying-denitrifying microbes, but I don't see a reasonable way to get that information. I might be wrong, but that seems to be an expensive proposition.

Did you find any evidence that it is not dangerous? That the situation in which a system may be brought due to carbohydrate dosing which I have described is not possible?

Where all this users properly informed and advised about the pro's and con's involved?

All information can be found in the links published by me in this threat. All information is based on approved references which can be consulted with one click. Most is thoroughly explained in this threat.

 

[Belgian Anthias]

That's possible. In addition, the ammonia-processing capacity might increase very rapidly in response to the input. At some point, we'll be arguing over wording here. The end result is the same.

I am sure that carbon dosing will have some impact on autotrophs. I am skeptical about the downside being significant, given the experiences reported here. I think we're done, pending data on what is happening. That data is going to be very expensive to produce, I'd guess, which is too bad. It'd be interesting to see what's happening.

How the the ammonia-processing capacity might increase very rapidly in response to the input when carbo dosing is stopped?
The only way to do so is stop feeding which is advisable.
It is a fact that autotroph nitrifiers need 15 days to double there nitrification capacity. If this capacity is brought back to 15 % instead of 60% because of carbo dosing it will take one month to reach the normal capacity needed.

All data is available as heterotrophic ammonia and nitrate reduction has been researched thoroughly during past decennia in university's all over the world. I have used research of Ebeling, J.M., Timmons, M.B., Bisogni, J.J., 2006. (Engineering analysis of the stoichiometry of photoautotrophic, autotrophic, and heterotrophic removal of ammonia–nitrogen in aquaculture systems. Aquaculture 257, 346–358. https://doi.org/10.1016/j.aquaculture.2006.03.019)
to help develop my point of view. The publication can be consulted http://www.baharini.eu/baharini/doku.php?id=nl:makazi:het_water:ammonium_reductie

The suppression of autotrophs by heterotrophs is a key factor in managing mixotropic biofilters and part of most studies about this subject. I advice to read some of these studies.

 

[Dan_P]

All data is available as heterotrophic ammonia and nitrate reduction has been researched thoroughly during past decennia in university's all over the world. I have used research of Ebeling, J.M., Timmons, M.B., Bisogni, J.J., 2006. (Engineering analysis of the stoichiometry of photoautotrophic, autotrophic, and heterotrophic removal of ammonia"“nitrogen in aquaculture systems. Aquaculture 257, 346"“358. https://doi.org/10.1016/j.aquaculture.2006.03.019)
to help develop my point of view. The publication can be consulted http://www.baharini.eu/baharini/doku.php?id=nl:makazi:het_water:ammonium_reductie

Yes this is good read if you want to know about the science behind carbon dosing but a somewhat more readable version was presented at the 6th International Conference on Recirculating Aquaculture. It is published here.

https://ejournals.lib.vt.edu/ijra/article/view/1336/1814

Figure 2 is important to put the ideas in this post in perspective. The bar chart reflects Jonathan's perspective. Unless the C:N ratio is very high, you always have some autotrophic activity. Ending carbon dosing suddenly when the system is heavily dependent on heterotrophic activity to remove nitrogen seems likely to produce an ammonia spike, but you haven't provided evidence or calculated a C:N ratio for a typical aquarium to show whether the typical aquarium heterotrophic:autotrophic ratio is on the edge of disaster. The notion to use care tapering off carbon dosing is sound advice. Whether a sudden cessation is dangerous has yet to be demonstrated.

Where I think we missed an important point in this discussion is that the ratio of heterotrophic:autotrophic may be predictive of a system's propensity to grow nuisance photoautotrophs such as diatoms, dinoflagellates, cyanobacteria and algae. The notion that nitrate and phosphate are predictive or are the cause of nuisance organism growth needs to be revisited. It might be more useful to think in terms of inadequate heterotrophic activity or a low C:N ratio as the cause of nuisance organism growth.

 

[Belgian Anthias]

Zmas

Zmas

Many zero emission marine aquaculture systems ( ZMAS) are managed with carbohydrate dosing and adjusted feeding. No markable nitrification and denitrification takes place in these systems. No filters are used exempt for the removal of detritus.
These systems are completely dependable of the carbohydrate doses and corresponding matched feeding rate.
How it is possible that no nitrification takes place in a system with a high carrying capacity and a very high ammonia production?
As there is no nitrate produced in the system in combination with a very high daily ammonia production, how the correct carbohydrate doses are calculated?
What will happen when dosing is not matched with the ammonia production ?

Of coarse one can not compare such ZMAS with a reef aquarium ( also a ZMAS) but the bio-chemical basics and principles are for both systems the same.

 

[Belgian Anthias]

Yes this is good read if you want to know about the science behind carbon dosing but a somewhat more readable version was presented at the 6th International Conference on Recirculating Aquaculture. It is published here.

https://ejournals.lib.vt.edu/ijra/article/view/1336/1814

Figure 2 is important to put the ideas in this post in perspective. The bar chart reflects Jonathan's perspective. Unless the C:N ratio is very high, you always have some autotrophic activity. Ending carbon dosing suddenly when the system is heavily dependent on heterotrophic activity to remove nitrogen seems likely to produce an ammonia spike, but you haven't provided evidence or calculated a C:N ratio for a typical aquarium to show whether the typical aquarium heterotrophic:autotrophic ratio is on the edge of disaster. The notion to use care tapering off carbon dosing is sound advice. Whether a sudden cessation is dangerous has yet to be demonstrated.

Where I think we missed an important point in this discussion is that the ratio of heterotrophic:autotrophic may be predictive of a system's propensity to grow nuisance photoautotrophs such as diatoms, dinoflagellates, cyanobacteria and algae. The notion that nitrate and phosphate are predictive or are the cause of nuisance organism growth needs to be revisited. It might be more useful to think in terms of inadequate heterotrophic activity or a low C:N ratio as the cause of nuisance organism growth.

Both publications are available and included in my article including a lot of other publications http://www.baharini.eu/baharini/doku.php?id=nl:makazi:het_water:ammonium_reductie

It is known that autotrophs do not care at all about the presence of heterotophs and that it is just a question of available organic carbon and competition for the same building materials. And there will be always autotrophs present in an aquarium, they will not be wiped out.
The problem is the difference in growth rate. They may be suppressed and drastic be reduced in a few hours to days, but they need time to reinstall when given the space. Autotrophic decay feeds heterotrops due increased availability of organics.

This threat is not about the influence of nitrate on the system but about how to have control over the nitrate production and removal in function of maintaining the carrying capacity needed. Most organism prefer ammonia above nitrite and nitrate as nitrogen source for celsynthesis. , Respiration is also a factor of big influence.
How to control nitrate and what is the safest way to do so.?
The fact that carbohydrate dosing will reduce the nitrification capacity is not a problem as long the carrying capacity is not changed. The problem is that when the dosing is interrupted the carrying capacity will change. When the change is to big it will have its effect and its consequences. Dangerous? A system that may loses a part of its carrying capacity from one day to an other, yes I find this situation dangerous. It is a risk one does not have to take, not for fine tuning the nitrate level.
When one messes with nature it has always consequences. It is important to know what may happen before starting messing with it.

 

[Dan_P]

, The problem is that when the dosing is interrupted the carrying capacity will change. When the change is to big it will have its effect and its consequences. Dangerous? A system that may loses a part of its carrying capacity from one day to an other, yes I find this situation dangerous. It is a risk one does not have to take, not for fine tuning the nitrate level.
When one messes with nature it has always consequences. It is important to know what may happen before starting messing with it.

The C:N ratio in the reference I quoted for complete heterotrophic N assimilation is 13:1. That means a 39:1 ratio of acetic acid to ammonia nitrgen. That corresponds to a volume of vinegar of 780 mL per gram of ammonia nitrogen. I am pretty sure no aquarist is at this level of dosing, and therefore, has not pushed their system into all heterotrophic activity. A large ammonia spike does not seem like a realistic danger. Beyond this point, estimating the size of the consequence of abruptly stopping carbon additions seems impossible. To this point in time carbon dosing does not seem to have increased aquarium issues, something to be expected if many of the systems were teetering on the edge of disaster.

I understand your concern about the risk of dosing and agree with the idea to understand before attempting to adjust aquarium conditions. We disagree on the severity of the risk of carbon dosing. I think the size of the risk is testable, maybe without endangering organisms other than bacteria.

 

[bertoni]

Did you find any evidence that it is not dangerous?

Yes. Years of experience with many, many tanks tell us that this approach is safe. That's as good as it gets with aquariums. In your opinion, it's dangerous or possibly dangerous. That's fine, but other people have different opinions, and what evidence we have says that carbon dosing can be done safely. Admittedly, the evidence is limited watching what happens to people's tanks rather than controlled experiments, but in the end, that's what we care about: how well the tanks perform. Aquarium science isn't going to get much funding for much beyond that.

Your references are interesting, but they do not tell us anything about the risks in our systems.