What do we really know about vinegar (carbon) dosing?

[Dan_P]

These are just some thoughts I had when I recently started carbon dosing. You have all read it before; the idea is to add a carbon source, which feeds the otherwise carbon-limited population of bacteria, which causes a reduction in N and P. And bacteria get skimmed out by the skimmer. But how much scientific evidence is there for this mechanism?

Literature on dosing a carbon source to bring down ammonia and nitrate can be found in the waste water treatment and recirculated aquaculture literature. Carbon dosing is not recognized as a phosphate reduction method because too little phosphate is removed. As for aquarium use, I haven’t come across scientific studies on this subject. Explanations about how carbon dosing works in aquaria seems to be inferred from waste water treatment and recirculated aquaculture studies.

Just one observation: Why does the skimmer go bonkers when vinegar dosing? When I added bottle bacteria before, this did not happen. Does vinegar act as a flocculant instead?

The foaming that occurs soon after addition of vinegar is likely an organic compound in the vinegar.

Also, the sheer mass of skimmed bacteria must be really high to reduce N and P significantly. When you have a refugium, you can grab a couple of handfuls of chaeto, and its dry weight is considerable. We know approx. the N and P content of chaeto and, hence, we know how much N and P we are removing. But if you were to dry out the skimmate, I wonder if you would get a lot of dry-weight substance out.

This a good point that is rarely brought up about when discussing the role of skimming. Bacteria dry weight mass removal by skimming is very small compared to the dry weight of macro algae used to control nitrate. I am not sure anyone has ever checked that enough macro algae mass is being generated to account for the reduced nitrate.

Perhaps many of the organisms that you grow with vinegar do not need to leave via the skimmate? Then, you could imagine binding up N and P in sponges and rock-bound bacteria. Anyhow, these are some thoughts to start a critical discussion. References to literature would be useful. @Randy Holmes-Farley @Lasse @taricha @Dan_P.

Good points. Nitrate could be leaving via reduction to nitrogen (see Lasse post) as well as becoming biomass in the aquarium. I don’t recall seeing anyone calculating the amount of biomass produced per ppm of nitrate removed. I suspect the generated biomass could not be visually detected. The dry weight of the white biofilm noted in some dosing situations probably isn’t enough to account for the nitrate reduction.

My feeling is that several mechanisms are responsible for removing nitrate when organic carbon is added to an aquarium.

 

[carri10]

I find this topic fascinating. There are some interesting points brought up in this thread. Carbon dosing to promote bacterial Biomass, consuming NO3 (vs mass of refugium algae, a very interesting calculation to do). Carbon dosing to drive anoxic denitrification.

I have a fundamental point that I can't get round. We say Carbon dosing works because tanks are Carbon limited. Sea reef water is, we've seen the data. But, I struggle to understand how a tank that gets fed 2-3 times a day, or more, if you drip in food for your Anthias etc, can be Carbon limited.
That is a whole heap of Carbon going in.
If organisms and filtration are able to remove that Carbon so quickly that the tank is limited, maybe just dial down the filtration, rather than dose vinegar?

I'm not arguing Carbon dosing doesn't work. There are plenty of tanks that show it does. The question is how?

 

[I never finish anythi]

Cheap distilled white vinegar will not cause skimmer to go bonkers.

Yep, I use vinegar and my skimmer does not go bankers .

 

[GlassMunky]

I find this topic fascinating. There are some interesting points brought up in this thread. Carbon dosing to promote bacterial Biomass, consuming NO3 (vs mass of refugium algae, a very interesting calculation to do). Carbon dosing to drive anoxic denitrification.

I have a fundamental point that I can't get round. We say Carbon dosing works because tanks are Carbon limited. Sea reef water is, we've seen the data. But, I struggle to understand how a tank that gets fed 2-3 times a day, or more, if you drip in food for your Anthias etc, can be Carbon limited.
That is a whole heap of Carbon going in.
If organisms and filtration are able to remove that Carbon so quickly that the tank is limited, maybe just dial down the filtration, rather than dose vinegar?

I'm not arguing Carbon dosing doesn't work. There are plenty of tanks that show it does. The question is how?

Im gonna take a wild guess here cause it’s early and my brains not fully there…..
but if it’s anything like plants and gardening, a lot of the carbon in the inputs are not in forms that are bioavailable to the organism (plant or coral or whatever) and are in other forms that require energy to use vs the organic acids that are much more readily taken up and that energy used to convert it to those forms is large.

 

[Dan_P]

I find this topic fascinating. There are some interesting points brought up in this thread. Carbon dosing to promote bacterial Biomass, consuming NO3 (vs mass of refugium algae, a very interesting calculation to do). Carbon dosing to drive anoxic denitrification.

I have a fundamental point that I can't get round. We say Carbon dosing works because tanks are Carbon limited. Sea reef water is, we've seen the data. But, I struggle to understand how a tank that gets fed 2-3 times a day, or more, if you drip in food for your Anthias etc, can be Carbon limited.
That is a whole heap of Carbon going in.
If organisms and filtration are able to remove that Carbon so quickly that the tank is limited, maybe just dial down the filtration, rather than dose vinegar?

I'm not arguing Carbon dosing doesn't work. There are plenty of tanks that show it does. The question is how?

A rough sketch of why aquaria carbon limited…

Carbon is limited to the heterotrophs we do not feed in an aquarium. Because most of the carbon in food is used for energy by heterotrophs, the fed organisms receive too much nitrogen and phosphorous in their food which they excrete and all the not fed organisms receiving this high level of nitrogen but nowhere near not enough carbon to utilize it, let it accumulate.

 

[Lasse]

I have a fundamental point that I can't get round. We say Carbon dosing works because tanks are Carbon limited. Sea reef water is, we've seen the data. But, I struggle to understand how a tank that gets fed 2-3 times a day, or more, if you drip in food for your Anthias etc, can be Carbon limited.
That is a whole heap of Carbon going in.
If organisms and filtration are able to remove that Carbon so quickly that the tank is limited, maybe just dial down the filtration, rather than dose vinegar?

I think we use the term organic carbon limited the wrong way -What we meen is "limited by readily available organic carbon" as @GlassMunky suggest below. We should use the term DOC limited instead

Im gonna take a wild guess here cause it’s early and my brains not fully there…..
but if it’s anything like plants and gardening, a lot of the carbon in the inputs are not in forms that are bioavailable to the organism (plant or coral or whatever) and are in other forms that require energy to use vs the organic acids that are much more readily taken up and that energy used to convert it to those forms is large.

A rough sketch of why aquaria carbon limited…

Carbon is limited to the heterotrophs we do not feed in an aquarium. Because most of the carbon in food is used for energy by heterotrophs, the fed organisms receive too much nitrogen and phosphorous in their food which they excrete and all the not fed organisms receiving this high level of nitrogen but nowhere near not enough carbon to utilize it, let it accumulate.

We must distinguish between pelagic and benthic heterotrophic bacteria here. The pelagic are more or less completely dependent on dissolved nutrients (DOC. DIP and DIN) while the benthic need bound organic nutrients but probably are able to use DOC if organic carbon is a limited factor (or difficult to access) It appears that it is more difficult for the benthic bacteria to access the bound organic carbon in solid organic matter than to take the shortcut of using DOC as a carbon source and thus more easily grow on the more readily available organic P and N found in solid organic material. The breakdown of solid organic material then seems to go faster - DOC thus also affects the growth of the benthic bacteria.

This rise the question if DOC in reality can play any important role as a tool for nutrient export before most of the solid organic matter in the aquarium is consumed because around 75 - 80 % of the bound organic P and N will be released as DIP and DIN (Read Dissolved Inorganic Phosphor = PO4 and Dissolved Inorganic Nitrogen = NH3/NH4 -> NO2 -> NO3)

Sincerely Lasse

 

[KGV]

Literature on dosing a carbon source to bring down ammonia and nitrate can be found in the waste water treatment and recirculated aquaculture literature. Carbon dosing is not recognized as a phosphate reduction method because too little phosphate is removed. As for aquarium use, I haven’t come across scientific studies on this subject. Explanations about how carbon dosing works in aquaria seems to be inferred from waste water treatment and recirculated aquaculture studies.


The foaming that occurs soon after addition of vinegar is likely an organic compound in the vinegar.



This a good point that is rarely brought up about when discussing the role of skimming. Bacteria dry weight mass removal by skimming is very small compared to the dry weight of macro algae used to control nitrate. I am not sure anyone has ever checked that enough macro algae mass is being generated to account for the reduced nitrate.



Good points. Nitrate could be leaving via reduction to nitrogen (see Lasse post) as well as becoming biomass in the aquarium. I don’t recall seeing anyone calculating the amount of biomass produced per ppm of nitrate removed. I suspect the generated biomass could not be visually detected. The dry weight of the white biofilm noted in some dosing situations probably isn’t enough to account for the nitrate reduction.

My feeling is that several mechanisms are responsible for removing nitrate when organic carbon is added to an aquarium.

I have done this back-of-the-envelope calculation once for my tank. I harvest about 12.8 grams of dry-weight chaeto every 2 weeks. I calculated that this should reduce my 670 L tank with 5.12 ppm NO3.

To put that into perspective, I estimated that 15 gram frozen mysis would add 0.83 ppm NO3 to this size tank.

 

[GARRIGA]

Been dosing NoPox on and off since late 2021 with no skimmer. Have even experimented with overdosing with only side affect being white bacterial blooms that dissipated quickly once I stopped. Test tank so no coral but nothing else is removing the bacterial. Do have an overly large biological media bed that comprises 25% of the tank volume. Not sure why there's this notion one needs a skimmer with carbon dosing. Perhaps in my situation the 25% media solves it yet it's my understanding most of the bacteria being pelagic heterotrophs.

At this point. Less concerned with why it works and satisfied with it works.

As a side note. I have noticed phosphates drop when overdosing NoPox. Use API test kits because this is rudimentary test and not seeking precision but it stays under 0.025 ppm and I've had nitrates as high as 160 ppm and phosphates near 2 ppm. Didn't test nitrites therefore unaware how accurate that nitrate test was but regardless doubt much if any nitrite exists since I've done this both after cycle to remove excess nitrates as well as several times after it was mature. Both with and without GHA present. Later I don't believe contributed to the reduction because I obtained the same results when no algae was present.

 

[Garf]

I have done this back-of-the-envelope calculation once for my tank. I harvest about 12.8 grams of dry-weight chaeto every 2 weeks. I calculated that this should reduce my 670 L tank with 5.12 ppm NO3.

To put that into perspective, I estimated that 15 gram frozen mysis would add 0.83 ppm NO3 to this size tank.

Dry weight as dried in an oven I assume? What temperature and for how long ? if you don't mind. I did my algae scrubber dry weight, long time ago at 110C for 3 hrs and dry weight was only 4-5% of squeezed dry weight.

 

[Randy Holmes-Farley]

But, I struggle to understand how a tank that gets fed 2-3 times a day, or more, if you drip in food for your Anthias etc, can be Carbon limited.
That is a whole heap of Carbon going in.
If organisms and filtration are able to remove that Carbon so quickly that the tank is limited, maybe just dial down the filtration, rather than dose vinegar?

I'm not arguing Carbon dosing doesn't work. There are plenty of tanks that show it does. The question is how?

I don't see any issue there, and while there is certainly uncertainty which organisms are the primary users, there's really no theoretical conundrums that I can see.

Carbon limitation has nothing to do with foods or feeding levels. It simply says that if you add more organic carbon, something will grow faster, and that something was organic carbon limited..

Take a reef tank that is not dosing organics. Bacteria and other organisms will expand in numbers until something limits their growth. In a solution meeting all their needs, bacteria grow so much that the liquid gets thick and very cloudy with bacterial.

So something in that reef tank is limiting their further growth, and organic carbon is a perfectly plausible and almost self proving mechanism since an organic overdose will often cause water hazy with bacteria.

So in that setting, adding more organic carbon allows more growth. Carbon limitation.

Filtration of what exactly? The organics removed by ANY of the mechanisms we use are NEVER like acetate or ethanol. They are natural biomolecules loaded with N and P and even S. Think Redfield ratio (for once it has a use).

So here's the theory: add an organic that contains no N or P. Export organics that contain N and P. N and P decline.

QED.

(and, of course, there is the possibility of denitrification as well)

 

[Dan_P]

I have done this back-of-the-envelope calculation once for my tank. I harvest about 12.8 grams of dry-weight chaeto every 2 weeks. I calculated that this should reduce my 670 L tank with 5.12 ppm NO3.

To put that into perspective, I estimated that 15 gram frozen mysis would add 0.83 ppm NO3 to this size tank.

To check my understanding, every two weeks 5 ppm is removed via Cheato harvest while feeding 0.83 ppm NO3 over two weeks?

 

[Koty]

Do you mean that there are more pelagic bacteria in the water column and that they are continuously skimmed out?

Sincerely Lasse

Yes. I guess I should not text from my cellphone. I would like to hope that they are pelagic bacteria.My corals think so...I can correlate between the amount of organic material added to the system, wether its carbon dosing or an "overdose" of frozen fresh mussels the skimmer lets me know in a few hours.

 

[Koty]

I don't see any issue there, and while there is certainly uncertainty which organisms are the primary users, there's really no theoretical conundrums that I can see.

Carbon limitation has nothing to do with foods or feeding levels. It simply says that if you add more organic carbon, something will grow faster, and that something was organic carbon limited..

Take a reef tank that is not dosing organics. Bacteria and other organisms will expand in numbers until something limits their growth. In a solution meeting all their needs, bacteria grow so much that the liquid gets thick and very cloudy with bacterial.

So something in that reef tank is limiting their further growth, and organic carbon is a perfectly plausible and almost self proving mechanism since an organic overdose will often cause water hazy with bacteria.

So in that setting, adding more organic carbon allows more growth. Carbon limitation.

Filtration of what exactly? The organics removed by ANY of the mechanisms we use are NEVER like acetate or ethanol. They are natural biomolecules loaded with N and P and even S. Think Redfield ratio (for once it has a use).

So here's the theory: add an organic that contains no N or P. Export organics that contain N and P. N and P decline.

QED.

(and, of course, there is the possibility of denitrification as well)

May be a simple way too explain is that its a carbon source that serves as fuel. Its oxidized by various fauna in your tank to convert it to the common energy "currency" ATP allowing everything alive in your tank to grow and consume nitrate to mainly build proteins and phosphate to build membranes and DNA (a bit simplified) The fish poop is indeed made of carbon but it is mostly "burned"

 

[KGV]

Dry weight as dried in an oven I assume? What temperature and for how long ? if you don't mind. I did my algae scrubber dry weight, long time ago at 110C for 3 hrs and dry weight was only 4-5% of squeezed dry weight.

Oven 60 degree for many hours and kept in a jar with silica beads. Made sure weight weight stayed the same for consecutive readings.

 

[flying4fish]

After more than 7 years of maintaining a reef tank, I suddenly found that I had elevated levels of NO3 and PO4 that were well beyond the ideal range. After a lot of reading I turned to carbon dosing. I used vodka and I also tried commercial dosing products. My NO3 came down after awhile but PO4, which was my main concern, didn't budge. In the meantime I had wild swings in my bacterial and algal communities. I also went through an alkalinity swing because, for some reason I cannot explain, my tank's alkalinity consumption dramatically dropped...since I was so used to a constant usage I wasn't testing very often and I lost a lot of corals. I also had some of the most crystal clear water I've ever seen, and at times the only growth on my glass was bacteria. Sometimes I had white bacteria and sometimes pink. Long story short, I think the results one will achieve with carbon dosing will vary a lot between individuals, because of the very different microbial and algal communities each tank is starting with. I eventually turned to GFO to drop my PO4, and that worked very well. I stopped carbon dosing and I don't think I would recommend it to anyone because of the unpredictable results it produces.

 

[Dan_P]

But, I struggle to understand how a tank that gets fed 2-3 times a day, or more, if you drip in food for your Anthias etc, can be Carbon limited.
That is a whole heap of Carbon going in.

Another quick sketch about organic carbon limitation.

Most of the carbon in food is converted to carbon dioxide, leaving an insufficient amount carbon to make heterotrophic biomass with the nitrogen in the food. That’s where nitrate accumulation comes from unless there is sufficient photosynthesis taking place and generating algae biomass (denitrification is another way to get rid of nitrogen and not make much biomass). It seems that many aquaria accumulate nitrate, meaning there is insufficient denitrification, photosynthesis and heterotrophic mass generation (aka, carbon limitation).

 

[Lasse]

Another quick sketch about organic carbon limitation.

Most of the carbon in food is converted to carbon dioxide, leaving an insufficient amount carbon to make heterotrophic biomass with the nitrogen in the food. That’s where nitrate accumulation comes from unless there is sufficient photosynthesis taking place and generating algae biomass (denitrification is another way to get rid of nitrogen and not make much biomass). It seems that many aquaria accumulate nitrate, meaning there is insufficient denitrification, photosynthesis and heterotrophic mass generation (aka, carbon limitation).

I have to change my motto (I am not young enough to know everything, but neither so old that I forgotten everything) to "I am not young enough to know everything, but I forget something"

Your totally 100 % right. The production of CO2 from organic carbon (From heterotrophs like fish, inverts, bacteria and other heterotroph organism) is the main reason why a saltwater aquarium in the long run will be limited in organic carbon compared with other nutrients. The produced CO2 will be lost to air but P has no air phase (at least in an aquarium). N has as NH3-N but its a minor and short-lived species of inorganic N - most inorganic N will end up as NO3-N


Sincerely Lasse

 

[bezj]

After more than 7 years of maintaining a reef tank, I suddenly found that I had elevated levels of NO3 and PO4 that were well beyond the ideal range. After a lot of reading I turned to carbon dosing. I used vodka and I also tried commercial dosing products. My NO3 came down after awhile but PO4, which was my main concern, didn't budge. In the meantime I had wild swings in my bacterial and algal communities. I also went through an alkalinity swing because, for some reason I cannot explain, my tank's alkalinity consumption dramatically dropped...since I was so used to a constant usage I wasn't testing very often and I lost a lot of corals. I also had some of the most crystal clear water I've ever seen, and at times the only growth on my glass was bacteria. Soetimes I had white bacteria and sometimes pink. Long story short, I think the results one will achieve with carbon dosing will vary a lot between individuals, because of the very different microbial and algal communities each tank is starting with. I eventually turned to GFO to drop my PO4, and that worked very well. I stopped carbon dosing and I don't think I would recommend it to anyone because of the unpredictable results it produces.

When nitrate goes down alkalinity goes up so definitely one to watch.

When I first started dosing Bacto balance in search of reducing nitrate I tested alkalinity daily and there was a lot of adjustment needed on All For Reef as a result.

Been dosing Bacto balance for 12 months now and it isn’t really nitrate related, my corals seem to low the stuff. Polyp extension is great on my SPS and LPS thrive.

I did build a nitrate destroyer (totally different thread!) which worked to well so it just acts as additional media area!

Can’t imagine not carbon dosing! For reference I’m dosing 5ml daily in to a 550 litre tank

 

[Koty]

So, carbon dosing is to pump energy into our tanks for bacteia to consume N and P and at the same time support the microbiome all over the tank and also feed all other creatures that directly can use this energy source. Chaeto or any othet macro algae grown in a refuge, takes up N & P as long as it grows. It also needs a supply of various elements to keep doing its job. The refuge also servs as a fishless nich that is crucial as it provides a constant supply of live food for the animals in the display. Coral reefs are nutrient poor (with some twists) in nature. For our tanks to imitate this condition we shoud use all the means to minimize the "half life" in the water column of all types of organic material that we add from the water colun

 

[Dan_P]

I have to change my motto (I am not young enough to know everything, but neither so old that I forgotten everything) to "I am not young enough to know everything, but I forget something"

Your totally 100 % right. The production of CO2 from organic carbon (From heterotrophs like fish, inverts, bacteria and other heterotroph organism) is the main reason why a saltwater aquarium in the long run will be limited in organic carbon compared with other nutrients. The produced CO2 will be lost to air but P has no air phase (at least in an aquarium). N has as NH3-N but its a minor and short-lived species of inorganic N - most inorganic N will end up as NO3-N


Sincerely Lasse

I keep reminding myself that I am not too old to learn