Looking for thoughts on organic carbon dosing and nitrate

[Randy Holmes-Farley]

Interesting.

Where do you take your water sample from?

 

[Lasse]

From the sump - downstream the reversed flow DSB. The DSB has a flow trough it at around 300 L/H. Its a loop from the main flow through the refugium (the DSB is the bottom of the refugium) The main flow is around 2000 l/H. The water is very well mixed in my aquarium. The DT is 300 L. I have 2 streamers in wave mode - around 8000 L(H. Two streamers in reef mode - around 4000 L /H and one smal in wave mode - around 1000 L/H

I´ have plan to follow up with measurements every day. Today I take it early because its Midsummer Eve here in Sweden - Skål

Sincerely Lasse

 

[Lasse]

Today no DOC since yesterday - NO3

NO2

I need to mention that the accuracy for the ULR marine NO2-N checker is ± 10 ppb which is equal to ± 0.039 mg/L NO2. The Hanna nitrate High Range NO3 checker has an accuracy of ± 2 ppm. Therefore - a single measurement says not so much - IMO - its the trend that it is important- IMO - my NO2 measurements do not say so much yet - they are basically the same (or could be) but the NO3 measurements show an increasing trend already now.

Sincerely Lasse

 

[jda]

My guess is that the traditional anoxic bacteria will develop as the no3 rises and then it will start to fall in a week or two.

Traditional is no the right word, but I don't know what else to call the bacteria... the ones that work to turn no3 into N gas without organic carbon.

 

[biom]

My guess is that the traditional anoxic bacteria will develop as the no3 rises and then it will start to fall in a week or two.

Traditional is no the right word, but I don't know what else to call the bacteria... the ones that work to turn no3 into N gas without organic carbon.

Most of the denitrifying bacteria are heterotrophs, and they all need some sort of organic carbon to perform denitrification. There are autotroph denitrificators that don't need organic carbon but they require other specific electron donors - sulfur, hydrogen gas etc., which are not that common in a reef tank. More on the sulfur denitrificators in Randy's article about nitrate.

Nitrate in the Reef Aquarium - REEFEDITION

Nitrate is an ion that has long dogged aquarists. It is typically formed in aquaria through the digestion of foods, and in many aquaria it builds up and can be difficult to keep at natural levels. In the past, many aquarists performed water changes with nitrate reduction as one of the primary...

www.reefedition.com

 

[jda]

Do they need OC to perform their jobs or to multiply in numbers? I add no OC and have enough denitrifying bacteria to keep just a trace of nitrate. I can see a bit of a jump if I add more fish (like .1 to .5) for a week, or so, but they always seem to multiply and bring no3 back down.

I have no doubt that you are right that they need OC, but I can assure you that you do not have to dose it, or anything. All that I have needed to do is to provide area for them to populate.

 

[biom]

Do they need OC to perform their jobs or to multiply in numbers? I add no OC and have enough denitrifying bacteria to keep just a trace of nitrate. I can see a bit of a jump if I add more fish (like .1 to .5) for a week, or so, but they always seem to multiply and bring no3 back down.

I have no doubt that you are right that they need OC, but I can assure you that you do not have to dose it, or anything. All that I have needed to do is to provide area for them to populate.

I have no doubt you manage to keep nitrate very low in your system without dosing OC.

What we are discussing here is if there is denitrification happening when carbon dosing or it is other process/es involved - nitrate/ammonium assimilation for example. And that is why Lasse is stopping OC dossing and measuring nitrate and nitrite concentration, once nitrate raised to a certain level he will start OC dosing again to see if there will be drop of nitrate and spike of nitrite - which can be proof denitrification is happening.

 

[Lasse]

I have no doubt that you are right that they need OC, but I can assure you that you do not have to dose it, or anything. All that I have needed to do is to provide area for them to populate.

You are right - in old - undisturbed - DSB there is a chance that some processes will produce the needed DOC as alcohols and Carbohydrate´s (sugar is a Carbohydrate) I have been working with processes in fish farms there we use these internal DOC productions as DOC sources for denitrification.

Sincerely Lasse

 

[GARRIGA]

Something that doesn't make sense to me is that we need to dose carbon when detritus is constantly breaking down. Wouldn't that normally provide what we dose manually or is that insufficient in the detritus normally produced. Was hoping since I trap detritus and allow it to naturally decompose that I would also be feeding the heterotrophs that utilize bound oxygen.

 

[Randy Holmes-Farley]

Something that doesn't make sense to me is that we need to dose carbon when detritus is constantly breaking down. Wouldn't that normally provide what we dose manually or is that insufficient in the detritus normally produced. Was hoping since I trap detritus and allow it to naturally decompose that I would also be feeding the heterotrophs that utilize bound oxygen.

When we dose organic carbon, it generally contains no N or P (except if we choose to dose amino acids). Most accumulating organics of natural origin, such as in detritus, will contain N and many will contain some P. So one does not expect similar effects.

 

[Lasse]

Something that doesn't make sense to me is that we need to dose carbon when detritus is constantly breaking down. Wouldn't that normally provide what we dose manually or is that insufficient in the detritus normally produced. Was hoping since I trap detritus and allow it to naturally decompose that I would also be feeding the heterotrophs that utilize bound oxygen.

Your right - the C/N/P ratio in our food is often so good that the C from the food should not be limited. But as I see it - much of the C in food (hence in the detritus) is much is more tightly chemically bound in the organic material than N and P - therefore the addition of easily accessible DOC becomes a shortcut for the decomposition.

I have experience with systems where we left the organic detritus so long under anaerobic conditions that the decomposition created both carbohydrates and alcohol that could serve as an organic carbon source for denitrification.

If you look at how oxygen-free decomposition works, the formation of methane gas is the last step in this decomposition. IMO - It shows how tightly some C is bound in organic matter

Internal DOC production may be the explanation why old untouched deep sand beds - as in @jda case - work

Sincerely Lasse

 

[Lasse]

Today measurements - NO3

NO2 measurements

Sincerely Lasse

 

[Lasse]

@biom

I do not think that we will see any NO2 change in this experiment when I start to dose again after I have reached 20 mg/L NO3. This of two reasons - I do not think there will be any intermediate NO2 if the denitrification process has enough of DOC - the other is that my second step in the nitrification process work like a charm - During this 24 hours the nitrification process has convert around 1.3 mg/L NH4 into NO3 without any NO2 upbuild. The NOB in my system will manage even NO2 from uncomplete denitrification with other words.

I can start to dose around 10 ml/day - the amount that seems to be enough for resulting in a NO3 concentration of around 3 mg/L

Sincerely Lasse

 

[jda]

^ I thought about this last night... the DOC in the tank might take over and you will make no nitrite. Do you still force water up through the substrate? If so, do you worry that you are pushing local DOC out of the sandbed that might be there in an undisturbed setting?

 

[Lasse]

^ I thought about this last night... the DOC in the tank might take over and you will make no nitrite. Do you still force water up through the substrate? If so, do you worry that you are pushing local DOC out of the sandbed that might be there in an undisturbed setting?

I´m aware of that - and it has indeed already happens but it was not trough the sand bed - it was when I backflush the plenum and let some of the water in the plenum coming out in the DT. Nowadays - I always clean with a direct flow out from the aquarium - if I need too.

Sincerely Lasse

 

[jda]

This direct injection flow plenum amazes me. I enjoy reading about it. I guess that my tank is just an old carbureted tank. Keep up the good work.

 

[biom]

@biom

During this 24 hours the nitrification process has convert around 1.3 mg/L NH4 into NO3 without any NO2 upbuild.

This is because 1.3 mg/l NH4 was spread out evenly for 24 hours - this is about 0,0009mg/L NH4 per minute - too small amount to be measured both for ammonia and resulting nitrite. Maybe if you pour all 1,3 mg/L NH4 at once and start constantly measure nitrite the results would be different.

That is why we are waiting nitrate to build up to 20 mg/L and then to pour the biggest amount OC you think is safe to convert as much as possible nitrate to N2 and start measuring nitrite and nitrate right after in short intervals. Maybe 35 ml OC? to convert about 10 mg/l NO3 by your calculations?

 

[biom]

Your right - the C/N/P ratio in our food is often so good that the C from the food should not be limited. But as I see it - much of the C in food (hence in the detritus) is much is more tightly chemically bound in the organic material than N and P - therefore the addition of easily accessible DOC becomes a shortcut for the decomposition.

That is correct to a some extent, but the main reason why our aquariums are organic carbon limited is the cellular respiration where most of organic carbon from the food is lost as CO2 (gas).

 

[Lasse]

That is why we are waiting nitrate to build up to 20 mg/L and then to pour the biggest amount OC you think is safe to convert as much as possible nitrate to N2 and start measuring nitrite and nitrate right after in short intervals. Maybe 35 ml OC? to convert about 10 mg/l NO3 by your calculations?

Nope - I can´t risk that - see @jda ´s post earlier in this thread. And I do not believe that unlimited DOC create momentary NO2 tops - I think you see them if there is not enough of DOC. Therefore - I will dose half the amount I know works in higher NO3 concentrations. Also - I have followed NH4 and NO2 during constant feeding through 12 hours feeding cycle in eel farms. When the filter was optimal used - NH4 always rise till the feeding was stopped (constant load of NH4) - the NO2 was also rising till 2 hours after feedings stop. When I stopped DOC dosing - I uncovered the mechanisms hidden behind the denitrification - constant production of NH4 in the system. This happens at the same time that I see no increase in NO2, which indicates that my NH4 load is significantly less than my filter capacity can handle, hence it can handle extra NO2 from incomplete denitrification. I think it is important to realize that its not possible the transfer what you see in nature with what you will see in a system constructed to optimize both nitrification and denitrification based on many years of experiences (and some studies) i have measured pure anaerobic system (no coupled nitrification) many times and the NO2 will only be a problem in the start and with to less DOC available. its the same with sulphur denitrification (its a autotrophic denitrification - no need for DOC) - you get NO2 build up in the beginning before you got enough of specialized bacteria.

Measurement for the day

NO3

NO2

Tendency is rather clear

Sincerely Lasse

 

[biom]

Nope - I can´t risk that - see @jda ´s post earlier in this thread. And I do not believe that unlimited DOC create momentary NO2 tops - I think you see them if there is not enough of DOC. Therefore - I will dose half the amount I know works in higher NO3 concentrations. Also - I have followed NH4 and NO2 during constant feeding through 12 hours feeding cycle in eel farms. When the filter was optimal used - NH4 always rise till the feeding was stopped (constant load of NH4) - the NO2 was also rising till 2 hours after feedings stop. When I stopped DOC dosing - I uncovered the mechanisms hidden behind the denitrification - constant production of NH4 in the system. This happens at the same time that I see no increase in NO2, which indicates that my NH4 load is significantly less than my filter capacity can handle, hence it can handle extra NO2 from incomplete denitrification. I think it is important to realize that its not possible the transfer what you see in nature with what you will see in a system constructed to optimize both nitrification and denitrification based on many years of experiences (and some studies) i have measured pure anaerobic system (no coupled nitrification) many times and the NO2 will only be a problem in the start and with to less DOC available. its the same with sulphur denitrification (its a autotrophic denitrification - no need for DOC) - you get NO2 build up in the beginning before you got enough of specialized bacteria.

Measurement for the day

NO3

NO2

Tendency is rather clear

Sincerely Lasse

Ok, of course it's your tank you should not risk anything .
Not sure what is the purpose of the experiment then?