Looking for thoughts on organic carbon dosing and nitrate

[Randy Holmes-Farley Verified Community Expert]

Corals in their natural environment are dissolved organic carbon (DOC) net positive. About 40% of the photosynthetically fixed carbon by zoox is excreted by the coral in the surrounding water as mucus. I would expect it is like this in the aquariums too. Corals will probably take some of the carbon dosed as acetate but will release back much more as mucus. Actually this could be the reason why I dont need to dose organic carbon to lower nitrates and phosphates in my tank full of corals - the corals themselves are dosing enough

Yes, I can believe that they are net excretors, at least in the absence of dosing readily metabolized organics such as acetate where we push those to unusually high levels.

 

[Timfish]

That certainly happens. N gets incorporated into many biomolecules such as proteins. But If it is a proposed explanation of a delay in seeing nitrate drop when organic carbon dosing, I'm not sure i see how it is an explanation.

What's happening with the detritus sponges may be shedding? I'd guess based just on gross morphology there's about a dozen species of cryptic sponges the commonly grow in reef systems. I'd expect some difference in how fast and how much stuff is pulled out of the water column and released as detritus. De goeij describes "piles" of detritus adjcent to cryptic sponges and in reef systems there's always dead spots somewhere in the aquascaping where water flow is minimal at best and detritus can collect. So how fast and how much of the detritus released is incorporated by the various organisms into a given systems food web? Can some of this detritus remain for weeks to months and act as a stockpile of N that has to be used up before adding labile DOC has an effect on overall nitrate levels?

 

[Randy Holmes-Farley Verified Community Expert]

What's happening with the detritus sponges may be shedding? I'd guess based just on gross morphology there's about a dozen species of cryptic sponges the commonly grow in reef systems. I'd expect some difference in how fast and how much stuff is pulled out of the water column and released as detritus. De goeij describes "piles" of detritus adjcent to cryptic sponges and in reef systems there's always dead spots somewhere in the aquascaping where water flow is minimal at best and detritus can collect. So how fast and how much of the detritus released is incorporated by the various organisms into a given systems food web? Can some of this detritus remain for weeks to months and act as a stockpile of N that has to be used up before adding labile DOC has an effect on overall nitrate levels?

I'm not disagreeing with any of that. I'm just not understanding how it relates to a perceived slow start to nitrate decline, unless you are suggesting that bacteria driven by increased organics such as acetate will not take up nitrate (or ammonia) and will instead consume detritus until it is exhausted and then take up nitrate. That doesn't really seem likely to me, but I cannot prove that it doesn't happen.

 

[Timfish]

I'm not disagreeing with any of that. I'm just not understanding how it relates to a perceived slow start to nitrate decline, unless you are suggesting that bacteria driven by increased organics such as acetate will not take up nitrate (or ammonia) and will instead consume detritus until it is exhausted and then take up nitrate. That doesn't really seem likely to me, but I cannot prove that it doesn't happen.

Why does it have to be the bacteria wait or metabolize something else before taking up Nitrate?

From De Goeij (2013) "The sponge-derived detritus was finally transferred into motile fauna and nonsponge filter feeders after 45 hours" . There's a host of small organisms that may feed off the detritus. Worms, for example, are ubiquitous to reef ssytems. It's my understanding they're waste will be ammonia and/or urea. Why can't the bacterioplankton start using nitrate right away but since of the pool of N stored in sponge detritus is being converted by worms or other organisms to ammonia and/or urea so it takes time for the nitrates in a system begin to be dropped.

 

[Randy Holmes-Farley Verified Community Expert]

Why can't the bacterioplankton start using nitrate right away but since of the pool of N stored in sponge detritus is being converted by worms or other organisms to ammonia and/or urea so it takes time for the nitrates in a system begin to be dropped.

The release of ammonia and/or nitrate from organisms consuming detritus is presumably happening all the time, and the nitrate concentration is the result of many processes, including the one you mention adding to it.

If the organic carbon dosing causes bacteria to take up nitrate, then nitrate will decline unless you are proposing that the worms etc. eating detritus become more active with organic carbon dosing/nitrate decline, and do so to a degree to offset the nitrate taken up by bacteria. That last part is what does not seem likely to me.

 

[biom]

I've started a simple experiment to dose organic carbon some two weeks ago exactly because of this thread, so thank you Randy.

This tank is new - about 4 months old, 26 gal about 20 gal water. 5 small fish, cuc, cleaner shrimp. LPS corals, trumpets, torch, favia, duncan, goni, and a easy SPS - stylophora "Milka" Feeding 1 cube frosen artemia daily. Live rocks, sand. Never dosed bacteria. Started N-cycle with few drops of mixture of ammonium, nitrate, urea and aminoacids (leftovers from a old experiment). Lights at full duration of 10 hours from the day one - Radion 15. Filtration Tunze 9004 skimmer, no sump, no mechanical filtration. There is some detritus build up already maybe because of lack of additional filtration.
Pests: Only one rock covered with turf algae, (why they are only on this rock is another story, maybe good to start new build thread)
Normal calcium, magnesium, alkalinity levels.
Dosing calcium formate 5 ml/day, and about 0.05 -0.1 ppm phosphate daily. I am dosing phosphate because of that rock with turf algae - I have a Lawnmower Blenny and I like him very much, great character, but he is eating only algae. Actually I think he hates algae as much as regular reefer do, because after he eats a lot of them making himself look as a fat tadpole he starts just scrubbing them out making my life harder to clean powerhead and skimmer from algae on a daily basis.

When started experiment NO3 was above10 ppm (Salifert), PO4 undetectable by Salifert (despite dosing - new sand, you know).

Started with 1 ml /day DIY version of NOPOX - ethanol, methanol, acetic acid, isopropanol, this time added to the recipe about 30 gram per liter glucose. Mixing nopox with 1 ml calcium carbonate prior dosing. Dosing after light is off. I have continued daily dosing of PO4 about 0.1 ppm when the light is on. The water became slightly cloudy for 2-3 days (not because of calcium carbonate) and on glass appeared whitish green slime, I decided to leave it like it is. The skimmer air intake clogged with bacterial buildup. No problems for fish or corals all of them were happy and breathing normal.

I have clearly noticed nitrate reduction already on the day 3 - it was between 5-10 ppm. At the day 5-7 it was about 2.5 - 5 ppm. At this point turf algae became bright green, started growing very fast, and started spreading on the rocks nearby, on the bottom appeared brown large spots of dino (Amphidinuim - checked under mic).
At this stage decided to only stop dosing PO4 and reduce the light duration from 10 to 8 hours. Continued dosing 1 ml/ day Nopox. Feeding the same 1 cube of brine shrimp. Nitrate reduction stopped at 2.5 ppm.

Today is day 14 of carbon dosing and Nitrate stays at about 2.5 ppm (salifert) for more than 7 days. What changed in the tank? Well, turf algae (and Blenny) are facing really hard times turf algae very noticeably declined for just one week, dinos are barely visible only for 1-2 hours during the light is on. And it looks the build up detritus on the rocks and bed is visually less now.
All the coral, fish and other inhabitants are happy (maybe except Blenny but he still have enough dying algae to eat).

I'll continue dosing 1 ml/day for another week and will report back.

 

[Randy Holmes-Farley Verified Community Expert]

Mixing nopox with 1 ml calcium carbonate prior dosing.

Nice experiment. Thanks for the info.

Why are you adding the calcium carbonate?

 

[HomebroodExotics]

The release of ammonia and/or nitrate from organisms consuming detritus is presumably happening all the time, and the nitrate concentration is the result of many processes, including the one you mention adding to it.

If the organic carbon dosing causes bacteria to take up nitrate, then nitrate will decline unless you are proposing that the worms etc. eating detritus become more active with organic carbon dosing/nitrate decline, and do so to a degree to offset the nitrate taken up by bacteria. That last part is what does not seem likely to me.

As far as I’m aware the fact that bacteria consume the carbon is a proven fact due to many scientific studies. It’s a proven method of waste management is it not? I’ve always been under the impression that it takes time for the bacterial colony to grow to start consuming excess nitrates.

 

[biom]

Nice experiment. Thanks for the info.

Why are you adding the calcium carbonate?

An old habit left from Zeovit I suppose they mix everything with Coral snow.
I am dosing calcium carbonate from time to time to clear the water and to help skimmer function. But for this experiment mostly because I am dosing after lights off and dont want this front drop of pH because of the acetic acid.

 

[Lasse]

Can some of this detritus remain for weeks to months and act as a stockpile of N that has to be used up before adding labile DOC has an effect on overall nitrate levels?

IMO - this happens all the time when different organics (organic detritus) is broken down by bacteria. Its not only a stockpile for N - it will also release P.

I agree with Randy that this process is not involved in " the slow start of nitrate take up" - at least not in a primary way. But - if the organic detritus built up in any way and in a spot there it is low or zero flow - the breakdown of the organic detritus can create anaerobic spots and in them - the former aerobic bacteria have to switch to anaerobic respiration and if NO3 is present - they will consume NO3 instead of oxygen. It means that this organic detritus build upp - they are probably responsible for an accelerated NO3 removal from the system. IMO - they can be indirect responsible for the delay - in that meaning that they need to be built up first before there can be a drastic reduction of the NO3 concentration.

Note - P can only come into the system as an import that we bring in - food, introduced organisms that die and so on. It can not be created internally from nothing. However - N can be introduced as inorganic N (NH3/NH4, NO2 or NO3) without our help through bacterial conversion of N2 into NH4 (mostly Cyanobacteria but even a bunch of anaerobic bacteria) It means that we probably have more N in the system that we bring in.

I have done some calculations on high quality dry fish food and the ration between N and P atoms are around 25:1. If our bacteria take up N/P in the same ratio - 25:1 N/P it means that the ratio NO3/PO4 molecules also is 25:1. I mol PO4 is exactly the same number molecules as 1 mol NO3. 1 Mol PO4 have the weight of around 93 g and 1 mol NO3 have the weight of 62 g. 25*62 g = 1550 g. 1550/93 = 16.5 If all P and all N in the food come out into the water column as PO4 and NO3 (not likely)

This means that if you start with 10 mg/l NO3 and 0.1 mg PO4 (weight ratio 100:1) and run it until PO4 is zero - you have only built in around 1.6 mg NO3 in the biomass of your bacteria. By the way - Congratulation if you can prove that with salifert NO3 test.

In this example I have calculated around the same atomic ration in the bacteria as in the food used - 25:1. However in this article (which is very useful in the whole discussion) the authors found that the atomic ratio ratio of exponentially growing plantonic bacteria cells was 6.7:1 (N/P). This correspond in my example with weight concentration a NO3/PO4 to 4,46 The article also show what´s happen with the atomic ratio if there is limitation in C, N or P. Very interesting reading. The study was done on planktonic bacteria - not on benthic bacteria that´s more likely in the aquarium but it surly indicate that biomass growth of bacteria can not be very effective in order to reduce high NO3 values in our aquarium.

Already the controlled introduction of N atoms (via the food) exceeds the number of N atoms per P atom in the bacterial biomass that will be formed when the C not is imitated by adding DOC. Added to this is the completely uncontrolled supply of N atoms via bacterial fixation (cyanobacteria and other bacteria)

I can only see one case there essential reduction of NO3 concentrations with help of bacterial biomass growth (assimilatory nitrate reduction) can work - add pure PO4 as well

Never the less after a while - DOC dosing really reduce NO3 but - IMO - this is due to other processes than strictly bacterial biomass growth. Denitrification and anammox as examples. These processes takes time to get started because they need mor or less an anaerobic environment.

IMO - as I try to say before - the lag period is because there are other processes than assimilatory nitrate reduction involved in the reduction of NO3 in our aquariums and its take time to have the established (slow growing organisms with special environmental demands)

When started experiment NO3 was above10 ppm (Salifert), PO4 undetectable by Salifert (despite dosing - new sand, you know).

Must ask for your nitrite level. A NO2 concentration of around 0.1 will give a wrong reading of around 5 ppm NO3 with salifert. 0.1 NO2 is not uncommon in a new started aquarium

I did a little calculation of the atomic ration in frozen artemia (Ocean Nutrition) and got the atomic ratio to 17:1. But still in comparison with the articles 6.7:1 - its a lot of more N atoms coming in that can be bind to bacterial biomass.


Interesting to note (together with the conclusion in some of the post above that corals are net producers of DOC.
That´s valid for macroalgae too and a study found that the average N/P atomic ration for 96 species of macroalgae was 30:1. Someone get any ideas?

Sorry for a long and complicated post

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

As far as I’m aware the fact that bacteria consume the carbon is a proven fact due to many scientific studies. It’s a proven method of waste management is it not? I’ve always been under the impression that it takes time for the bacterial colony to grow to start consuming excess nitrates.

I do not know that it is proven that bacteria are the primary and certainly not the sole users in a reef tank, but I was not suggesting here that they were not.

I do not believe, however, that added organics are accumulating for weeks in systems, while bacteria slowly ramp up. That would explain some folks long lag time, but I don't think it is plausible that bacteria do not ramp up rapidly in a matter of a few days. It only takaes the fastest growing species to do the trick. It's not like we are waiting from some rare and slow growing bacteria to expand in numbers.

 

[HomebroodExotics]

I do not know that it is proven that bacteria are the primary and certainly not the sole users in a reef tank, but I was not suggesting here that they were not.

I do not believe, however, that added organics are accumulating for weeks in systems, while bacteria slowly ramp up. That would explain some folks long lag time, but I don't think it is plausible that bacteria do not ramp up rapidly in a matter of a few days. It only takaes the fastest growing species to do the trick. It's not like we are waiting from some rare and slow growing bacteria to expand in numbers.

How do we know it’s not from a slow growing bacteria though? Has that been proven? If I’m understanding you correctly you say any bacteria will perform denitrification?
I’ve always thought of it as the carbon speeds up their metabolism and the bacteria have to consume their primary source of foods first (no clue what that may be) and then they will consume nitrates. But I could be completely wrong on this.

 

[Randy Holmes-Farley Verified Community Expert]

How do we know it’s not from a slow growing bacteria though? Has that been proven? If I’m understanding you correctly you say any bacteria will perform denitrification?
I’ve always thought of it as the carbon speeds up their metabolism and the bacteria have to consume their primary source of foods first (no clue what that may be) and then they will consume nitrates. But I could be completely wrong on this.

Why would it be from a slow growing one when there undoubtedly are fast growing ones around?

There are lots of studies showing lots of different bacteria and other organisms take up acetate, and that in the study below, marine bacterial populations shifted considerably in only 8-12 h after adding acetate. This study happened to be deep sea bacteria at various temps, but I think the same will happen in surface samples

Identification and activity of acetate-assimilating bacteria in diffuse fluids venting from two deep-sea hydrothermal systems

This is the first cultivation-independent study using stable isotopic and molecular tools addressing the heterotrophic potential of free-living microbes in

academic.oup.com

"In the 4 °C and 37 °C diffuse fluids from the Manus Basin the microbial communities shifted within 8–12 h from Epsilonproteobacteria- to Gammaproteobacteria-dominated communities. "

 

[HomebroodExotics]

Why would it be from a slow growing one when there undoubtedly are fast growing ones around?

There are lots of studies showing lots of different bacteria and other organisms take up acetate, and that in the study below, marine bacterial populations shifted considerably in only 8-12 h after adding acetate. This study happened to be deep sea bacteria at various temps, but I think the same will happen in surface samples

Identification and activity of acetate-assimilating bacteria in diffuse fluids venting from two deep-sea hydrothermal systems

This is the first cultivation-independent study using stable isotopic and molecular tools addressing the heterotrophic potential of free-living microbes in

academic.oup.com

"In the 4 °C and 37 °C diffuse fluids from the Manus Basin the microbial communities shifted within 8–12 h from Epsilonproteobacteria- to Gammaproteobacteria-dominated communities. "

Just because something consumes acetate doesn’t mean it contributes to denitrification though? Or is that what that means?

 

[biom]

I do not believe, however, that added organics are accumulating for weeks in systems, while bacteria slowly ramp up. That would explain some folks long lag time, but I don't think it is plausible that bacteria do not ramp up rapidly in a matter of a few days. It only takaes the fastest growing species to do the trick. It's not like we are waiting from some rare and slow growing bacteria to expand in numbers.

My experiment support this - next morning after first dose there were cloudiness in the water which indicates bacteria were already responded to elevated DOC levels and reproduced in mass. That cloudiness lasted few days and slowly disappeared lasting few hours after every dosing and at Day 10 was not visible at all which means this cloud forming free swimming bacteria were replaced by the other possibly benthic or anaerobic strains.

 

[Randy Holmes-Farley Verified Community Expert]

One thing I don't recall being discussed in this thread is a trace element limitation on bacterial growth. That could also explain high variability from tank to tank since trace element availability is quite variable.

Use of Trace Metals in: Marine Bioremediation: A Need for Fundamental Knowledge - Opportunities for Environmental Applications of Marine Biotechnology - NCBI Bookshelf

www.ncbi.nlm.nih.gov

"Besides the major algal nutrients (nitrogen, phosphorus, and silicon), marine organisms require trace elements—chiefly trace metals such as manganese, iron, cobalt, nickel, copper, and zinc—for growth. "

 

[HomebroodExotics]

My experiment support this - next morning after first dose there were cloudiness in the water which indicates bacteria were already responded to elevated DOC levels and reproduced in mass. That cloudiness lasted few days and slowly disappeared lasting few hours after every dosing and at Day 10 was not visible at all which means this cloud forming free swimming bacteria were replaced by the other possibly benthic or anaerobic strains.

Yes but did you have zero nitrates after the bacterial cloud was gone?

 

[Randy Holmes-Farley Verified Community Expert]

My experiment support this - next morning after first dose there were cloudiness in the water which indicates bacteria were already responded to elevated DOC levels and reproduced in mass. That cloudiness lasted few days and slowly disappeared lasting few hours after every dosing and at Day 10 was not visible at all which means this cloud forming free swimming bacteria were replaced by the other possibly benthic or anaerobic strains.

Thanks. Yes, that makes sense. Some folks have overdosed organics and get rapid blooms:

March 23:

"So, I may have primed my doser for a 3 hour period. Which means I may have overdosed my tank with 180 ml of vodka into a 350 gallon salt water volume. What should I be worried about over the next few days. Initially I was worried about oxygen crash due to bacterial bloom (how long does it take for bacterial bloom?)"

March 24

"Well, just checked and tank is extremely cloudy can barely see into it. "

Vodka Overdose: What to worry about?

Thanks, I've been in this hobby long enough to not panic. My skimmer did produce more skimmate rather quickly. As of this morning at 4:50 am my ph hit 7.8. Which to my basic understanding of ocean water is not toxic to corals or fish. However, that is the lowest ph I've ever seen in my tank...

www.reef2reef.com

 

[biom]

Must ask for your nitrite level. A NO2 concentration of around 0.1 will give a wrong reading of around 5 ppm NO3 with salifert. 0.1 NO2 is not uncommon in a new started aquarium

Nitrite and ammonium were both zero (salifert) when experiment started did not measure it after.
By the way maybe I am totally wrong but I think I can see difference in the color formation of the Salifert NitrAte test in presence of NitrIte - the solution becomes bright pink almost immediately instead of slowly coloring up and the color is somehow more deep purple- pink than in presence of only nitrate.

 

[biom]

One thing I don't recall being discussed in this thread is a trace element limitation on bacterial growth. That could also explain high variability from tank to tank since trace element availability is quite variable.

"Besides the major algal nutrients (nitrogen, phosphorus, and silicon), marine organisms require trace elements—chiefly trace metals such as manganese, iron, cobalt, nickel, copper, and zinc—for growth. "

Thanks for posting this, I forgot to mention that I am daily dosing exactly this trace metals except cobalt during the experiment + iodine