Looking for thoughts on organic carbon dosing and nitrate

[Randy Holmes-Farley]

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

Thanks. Those comments, most of which I do not disagree with, do not alter my opinion of it not being especially relevant to our situations.

 

[Randy Holmes-Farley]

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

How much of each were you dosing?

 

[Lasse]

Thanks, Lasse.

I do not know if you have seen my experiment with this bed and NO3 concentrations contra dosing 8% ethanol. You can follow it in my build thread. here.

This is my actual graph. Last days I run out of ethanol without notice it. Rise to 4.6 ppm NO3

Sincerely Lasse

 

[cvicente]

Thanks. Those comments, most of which I do not disagree with, do not alter my opinion of it not being especially relevant to our situations.

Just food for thought, in many systems including mine carbon dosing do not lower nitrate nor orthophosphate at recommeded dosages. As I stated in previous posts if I increase OC to the point were NO3 & PO4 reduction is detectable by hobby kits my Acros and Stylophoras start to RTN and people should be aware of this possibility. We all agree that not only the setup of every tank is different but the microbiology of every tank is different. Systems can behave completely different to OC dosing. Maybe I have a strain of bacteria in my system that turns pathogenic at very low OC levels, who knows. Honestly is good to know the science behind it but running a healthy growing reef it's all that matters to me.

 

[Randy Holmes-Farley]

Just food for thought, in many systems including mine carbon dosing do not lower nitrate nor orthophosphate at recommeded dosages. As I stated in previous posts if I increase OC to the point were NO3 & PO4 reduction is detectable by hobby kits my Acros and Stylophoras start to RTN and people should be aware of this possibility. We all agree that not only the setup of every tank is different but the microbiology of every tank is different. Systems can behave completely different to OC dosing. Maybe I have a strain of bacteria in my system that turns pathogenic at very low OC levels, who knows. Honestly is good to know the science behind it but running a healthy growing reef it's all that matters to me.

I certainly do not doubt that some tanks may get problems from high doses of organics, and organic carbon dosing alone may not solve all nitrate and phosphate issues.

What organic were you dosing?

 

[cvicente]

I certainly do not doubt that some tanks may get problems from high doses of organics, and organic carbon dosing alone may not solve all nitrate and phosphate issues.

What organic were you dosing?

Currently Tropic Marin Elimi NP in the denitrator, 1.1ml on every cycle (4 daily cycles) In the past I have dosed vodka, methanol, 5% white vinegar and NoPox. When I dosed these directly to the tank all of them caused RTN. The only thing that has worked for me is dosing OC through the denitrator.

 

[jda]

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

What I got from these responses is threefold. First: I have talked with them some before and they seem to fully understand the differences between the ocean and captive systems, like they did here. He has written much about corals having something like 100K different types of bacteria in them and I have always wondered if all of those stay alive in our tanks, but their research in nature is more important to study, IMO. Second: my theory that airing out a home is far superior to using other methods to keep pH up down feels better. This used to be just from experience, but seems that o2 might be a reason to consider air exchange. Perhaps I misunderstood or even an oxygen depleted home can still fully oxygenate a tank. Third: shallow water corals in the coral triangle thrive more than deeper water specimens of the same species which is widely believed to be with a wider spectrum of light available. Gonna need to read about oxygen, macroalgae and DOC now, or if they even considered energy from light in Arks.

Sorry for putting about 10-25 different studies and articles together.

 

[jda]

I do not know if you have seen my experiment...

Do you happen to have any thoughts why some anoxic beds work to keep no3 at barely a trace in some tanks and you need to use OC to do the same? I am fascinated by this.

My first thought was bioload, but I can double my fish load, double my food and I would still have .1, or so no3.

 

[Lasse]

Is it an old undisturbed beds?

Sincerely Lasse

 

[jda]

Thanks. Those comments, most of which I do not disagree with, do not alter my opinion of it not being especially relevant to our situations.

Do you not feel that it is relevant that the increase in OC might cause the heterotrophs to grow out of control at first, consume other things which need time to rebound to start using no3 and po4 again? This is the basis of my theory on OC dosing, but I will stop typing it if completely impossible. Dr. Rowher indicated this in the email, and I have read about the possibility in a lot of places.

 

[jda]

Is it old undisturbed beds?

Sincerely Lasse

In my case, yes and no. My sandbed is quite old. I do, however, vacuum small sections of it about every 4 years to where I get it all over the course of 12 months - the areas that I can get to. I love most of what Dr. Ron tried to do, but I found that the inert grey gunk/sludge in the sand gummed up the works to where microfauna and water could not efficiently get to the the depths or move around as much. That grey sludge/gunk did not cause any issues and I kept my sand/rock relative free of po4. I vacuum the sludge out.

I guess in terms of reef2reef, up to 4 years is probably "old and undisturbed," but probably not in your terms.

 

[Max93]

How much of each were you dosing?

I started vodka at .08mls based on the chart attached. I ended at 2.1, and I took it much slower than the chart due to all the warnings I’ve read here that vodka can be super strong. But after reading another thread after dosing vodka for over a month, I decided to try the multiple carbon sources approach, and switch to nopox since it’s a mix of vodka vinegar and something else.
I started dosing nopox per manufacturer recommendation, and undersized my tank for caution. Started at 21ml/day and my nitrates dropped quickly over 3 weeks. Currently I am dosing 15ml and plan on reducing it to 10ml when my nitrates are at 5.0

 

[Randy Holmes-Farley]

Do you not feel that it is relevant that the increase in OC might cause the heterotrophs to grow out of control at first, consume other things which need time to rebound to start using no3 and po4 again? This is the basis of my theory on OC dosing, but I will stop typing it if completely impossible. Dr. Rowher indicated this in the email, and I have read about the possibility in a lot of places.

Lots of things are possible, and in the case of cvicente, it sounds like he has a pathogenic strain of bacteria in the tank that revs up when organic carbon dosing./ That's always been a concern of mine (and others), but doesn't seem to manifest itself very often.

"Out of control" heterotrophs sounds like exactly what we want to happen, just not of a kind that causes harm to corals. It may be that they get their N for a while from other sources until those run out. Then they start to take up nitrate. That may be a significant part of the delay, although I wouldn't assume that are always substantial levels of other excess N sources available.

 

[PensacolaReefKeeper]

Despite my questions above, I do carbon dose a little to provide food and create another nutrient pathway. My 90 gets 20ml of vinegar per day. Nitrate stays at about 10 ppm at this dose but phosphate climbs slowly. If nitrate starts to rise because I'm feeding heavier or because I forgot to dose the vinegar for too long... again..., I double the dose until it hits 10 ppm again. Seems simple enough. I dose LC to reduce phosphate when it gets above .1 ppm.

I don't see a slow response to doubling the dose. I don't mess with it until nitrate hits around 25 ppm, and I can be back at around 10ppm in less than 2 weeks.

You dose what to decrease phosphate?

 

[Lasse]

I guess in terms of reef2reef, up to 4 years is probably "old and undisturbed," but probably not in your terms.

Yes its old. In very old sand beds you can´t exclude an internal production of different DOC:s like sugar and alkohols. Different anaerobic organisms produce these during the breakdown process. You als get some type of "osmosis" between the water and sand bed - NO3 is transported down to the more NO3 free layers in the bed. I have been working with this in fish farms and it took around 2 months befor unstirred sediments start to both produce its own DOC:s and proceed with denitrification. But it was a very high organic load.

I had hope that I could create such a system below my reversed flow sand bed but till now - I´m still depended of external addition of DOC.

Sincerely Lasse

 

[ReefGeezer]

You dose what to decrease phosphate?

I dose Lanthanum Chloride (LC) if phosphate gets over .15 ppm. It has not done that in a very long time though.

Inorganic phosphate stays between .03 and .08 these days. I don't use any filtration basis to export or bind phosphate. My tank is pretty mature now. I think the phosphates are being bound in the growth of corals and other organisms. I also try to dose a little phytoplankton twice a week. When I remember to do so, I'm sure that binds a little that gets swept up in the skimmer or consumed by other organisms.

Additionally, I have noticed that phosphate stays closer to the .03 ppm end of the range when I use a calcium carbonate solution (DIY Coral Snow) and MB7 (Brightwell MicroBacter 7) on a weekly basis. I don't know if that is an accurate observation or just wishful thinking though. I dose it for water clarity and Cyano prevention. If it does lower the phosphate a little, it is a bennie.

 

[Max93]

I had a vermitid snail explosion once I started dosing vodka, not sure if it was just the fact that my nitrates where at 30 when I began, and it was just the vermitids already in the process of growing and now that the nitrates are under control their population appears to be declining.

 

[Randy Holmes-Farley]

I had a vermitid snail explosion once I started dosing vodka, not sure if it was just the fact that my nitrates where at 30 when I began, and it was just the vermitids already in the process of growing and now that the nitrates are under control their population appears to be declining.

They may well have consumed suspended bacteria, like other filter feeders. I had them too, and it may be a potential side effect in some cases, of organic carbon dosing and the subsequent rise in bacteria.

 

[taricha]

So I did some data mining from the last 3 pages of @Lasse build thread. And I already considered Lasse's setup to be a best possible case - but crunching the numbers looks impossibly good.
Like 2 moles of Carbon removes 1 mole of Nitrogen, good.

Left chart is where I took different stretches of Lasse's data where he did various set volumes of 8% ethanol added fro a few days at a time.
When he doesn't dose any, NO3 climbs at between 2.5 to 4 ppm NO3 per day.
When he doses 18mL/day through his sand, NO3 drops around 2.5-3ppm per day.
The amount dosed is in mL of 8% ethanol (I interpret this as like 1/5 vodka) into 310L system.
The right chart is me trying to convert all those to moles/L of Carbon and Nitrogen.
(I'm not even sure that data is theoretically possible. Maybe Lasse can spot my error)


@Dan_P data with dumping vinegar into the water was more in the real world, like 40 moles C per 1 mole NO3 removed.

 

[Randy Holmes-Farley]

Here’s the balanced denitrification for ethanol.

12 NO3– + 5 CH3CH2OH + 12 H+ → 10 CO2 + 6 N2 + 21 H2O

Of course, it assumes no N incorporated into organics of tissues of bacteria and other organisms.