What carbon sources are more selectively digestible?

[taricha]

Premise of the question is that acetate and glucose are digestible by seemingly everything. You can find academic papers using acetate and glucose to grow micro- and macroalgae. Corals, sponges all readily consume acetate. This makes it ideal for many applications. (anyone ever tried growing corals in the dark on acetate? nevermind - another thread for another time.)
However one application of Carbon dosing is to feed bacteria with a desire to reduce algae growth. So obviously a carbon source that is known to be used to grow algae mixotrophically may not be the best choice for that emphasis.
What carbon sources might be a good option in terms of growing bacteria well, but being of low/no value to algae?

 

[Randy Holmes-Farley Verified Community Expert]

That's an interesting question that I do not know the answer to. I will say that at very high doses of vinegar, high enough to make the water hazy, caulerpa racemosa grew as fast or faster than ever, suggesting it was able to take it up.

One might find an organic that few bacteria consume, and no algae, but that may also block other desirable organisms from consuming it (corals, sponges, clams, etc.). That may or may not matter to the users, depending on their goals.

 

[Miami Reef]

From @Lou Ekus

NP Bacto Balance:

My understanding, as it has been explained to me by my team in Germany, is that most (not exclusively but most) of the algae and bacterial critters that we would prefer NOT to grow in our systems, have much better mechanisms for utilizing monomers than anything that is longer carbon chains. They just don't have good ability to break those longer chains down to the monomers they need. While the good guys (algae and bacteria) that are helpful to us have much better mechanisms for breaking those longer chains down to the monomers they utilize. So if you add mostly carbon chains that are more than monomers, you "target" and focus that nutrition on the beneficial critters we like to see multiply and help our closed tank system biome.

What carbon source in NP Bacto Balance?

What type of carbon source does NP Bacto Balance from Tropic Marin use?

www.reef2reef.com

Maybe @Hans-Werner can explain if he thinks this product fits the criteria you are wondering about.

 

[Tcook]

Astronauts

 

[Dan_P]

Premise of the question is that acetate and glucose are digestible by seemingly everything. You can find academic papers using acetate and glucose to grow micro- and macroalgae. Corals, sponges all readily consume acetate. This makes it ideal for many applications. (anyone ever tried growing corals in the dark on acetate? nevermind - another thread for another time.)
However one application of Carbon dosing is to feed bacteria with a desire to reduce algae growth. So obviously a carbon source that is known to be used to grow algae mixotrophically may not be the best choice for that emphasis.
What carbon sources might be a good option in terms of growing bacteria well, but being of low/no value to algae?

I am thinking there may not be big selectivity lever here when dosing carbon to feed bacteria to deplete nitrogen. The added carbon will not benefit algae as a energy source because the algae is likely suffering from a near photo inhibition effect from the high ratio of light intensity to nitrogen concentration.Also, except for cyanobacteria, carbon dosing an aquarium does not seem to be correlated with enhanced algae growth. If it were, the effect could also be explained by a synergistic effect of an increased bacterial metabolite concentration that benefits algae growth, for example, a vitamin or trace element siderophore.

 

[taricha]

From @Lou Ekus

NP Bacto Balance:

The thought of alginate or maybe other biopolymers had crossed my mind.
If its purpose in algae is energy storage, then algae would easily be able to break it down as food. But if it is just structural like cellulose, then algae might not be able to consume it as food, while bacteria certainly can.
Edit: I see NP Bacto is not from algae, but their Reef actif product does contain some alginate.

 

[taricha]

I am thinking there may not be big selectivity lever here when dosing carbon to feed bacteria to deplete nitrogen. The added carbon will not benefit algae as a energy source because the algae is likely suffering from a near photo inhibition effect from the high ratio of light intensity to nitrogen concentration.Also, except for cyanobacteria, carbon dosing an aquarium does not seem to be correlated with enhanced algae growth. If it were, the effect could also be explained by a synergistic effect of an increased bacterial metabolite concentration that benefits algae growth, for example, a vitamin or trace element siderophore.

Good argument, the flip side is that if I compare equal carbon of acetate to ethanol, I get less visible bacterial growth with acetate (Skimmate, film on glass). I'm reasoning that because the acetate is so widely consumed by everything, there's less uptake by bacteria.
So whether other organisms need the carbon or not, they seem to grab it when it's there in an available form.

 

[Dan_P]

Good argument, the flip side is that if I compare equal carbon of acetate to ethanol, I get less visible bacterial growth with acetate (Skimmate, film on glass). I'm reasoning that because the acetate is so widely consumed by everything, there's less uptake by bacteria.
So whether other organisms need the carbon or not, they seem to grab it when it's there in an available form.

I follow the reasoning and like the provocative thought. Let’s add “we assume lower bacteria growth rate means lower availability than ethanol”.

In addition to acetate concentration being lower because of competition for it, some of the lower growth could also be a result of (1) the lower energy content of acetate, and (2) that it takes more energy to get the acetate anion across the bacterial membrane. In addition, if the carbon source needs to enter a biofilm to be consumed, ethanol could diffuse faster through it then the hydrated acetate anion. I propose that the bulk of carbon uptake happens on surfaces, i.e., biofilms, not in the water. So diffusion rate limited growth might be detectable. This would mean that the stuff we collect on filters and in the skimmate are flocs and dispersed bacteria from biofilms.

 

[Dan_P]

Premise of the question is that acetate and glucose are digestible by seemingly everything. You can find academic papers using acetate and glucose to grow micro- and macroalgae. Corals, sponges all readily consume acetate. This makes it ideal for many applications. (anyone ever tried growing corals in the dark on acetate? nevermind - another thread for another time.)
However one application of Carbon dosing is to feed bacteria with a desire to reduce algae growth. So obviously a carbon source that is known to be used to grow algae mixotrophically may not be the best choice for that emphasis.
What carbon sources might be a good option in terms of growing bacteria well, but being of low/no value to algae?

While we are on the subject, just wanted to remind us that we still have not resolved the question of why we typically dose and dose and dose before seeing a nitrate reduction, whether the carbon source is ethanol or acetate. Is the apparent tipping point, where some higher dose finally kicks off nitrate reduction, the concentration of organic carbon where competition for the carbon dose is sated and the bacteria have enough to grow?

 

[taricha]

In addition to acetate concentration being lower because of competition for it, some of the lower growth could also be a result of (1) the lower energy content of acetate, and (2) that it takes more energy to get the acetate anion across the bacterial membrane. In addition, if the carbon source needs to enter a biofilm to be consumed, ethanol could diffuse faster through it then the hydrated acetate anion.

good point that these observations have hard to untangle causes.
I need to add thinking about energy comparisons - I don't have a good feel for that - and not just equal carbon comparisons.

 

[jda]

While we are on the subject, just wanted to remind us that we still have not resolved the question of why we typically dose and dose and dose before seeing a nitrate reduction, whether the carbon source is ethanol or acetate. Is the apparent tipping point, where some higher dose finally kicks off nitrate reduction, the concentration of organic carbon where competition for the carbon dose is sated and the bacteria have enough to grow?

My theory has always been that you are growing heterotrophs with the OC... so they start to eat other things and get their building blocks from those other things to multiply and don't need to use the N sources in the water column. The lag is from the food that needs to grow but now has lower numbers from the savage eating that the heterotrophs put on them so it takes a while to catch back up... then it will start to consume the N sources like you are expecting.

 

[Dan_P]

good point that these observations have hard to untangle causes.
I need to add thinking about energy comparisons - I don't have a good feel for that - and not just equal carbon comparisons.

Once again your posted question was like tossing a stone into a quiet pond: a whole bunch of ripples that have not played out yet.There is more for us to consider when trying to answer your question.

The optimum carbon source can be different across species. What works for your system might be less effective in my system. I have no idea if this a big effect. A second thought is that the observed bacteria growth you mentioned might not be the growth that is responsible for nitrate reduction. Maybe what you see are the heterotrophic bacteria depleting the oxygen and enhancing dentrification by a another species (This is your idea from Randy’s thread examining why dosing takes so long to have an effect).

 

[Dan_P]

My theory has always been that you are growing heterotrophs with the OC... so they start to eat other things and get their building blocks from those other things to multiply and don't need to use the N sources in the water column. The lag is from the food that needs to grow but now has lower numbers from the savage eating that the heterotrophs put on them so it takes a while to catch back up... then it will start to consume the N sources like you are expecting.

Yes, this scenario definitely needs to be considered.

Just to clarify, adding organic carbon allows certain bacteria to eat things that they might otherwise eat, like nitrogen containing polymers, that have a poor ratio of energy production versus energy input to digest. When the polymers run out, nitrate is needed for continued growth of all these bacteria.

 

[Shon]

Since we can DNA test for bacteria strains, I wonder how far off we are from having their personal lunch schedules?

Out of curiosity..

On using bacteria for nitrogen compound removal: Anyone notice if a higher hydrogen or oxygen to carbon ratio performed better? Or a higher carbon ratio to hydrogen/oxygen? Does the ratio even matter?

Some examples..
Ethenol= C2 H4 O
Acetic Acid= C2 H4 O2
Ascorbic Acid= C6 H8 O6
Alginic Acid= C6 H8 O6
Glucose= C6 H12 O6
..to the bigger..
HPMC= C56 H108 O30
Tannic Acid= C76 H52 O46

I know terrestrial plants can use tannin (like the poplar tree) but not cellulose (like HPMC). Hmm..

This conversation is above my head honestly.

 

[Dan_P]

My theory has always been that you are growing heterotrophs with the OC... so they start to eat other things and get their building blocks from those other things to multiply and don't need to use the N sources in the water column. The lag is from the food that needs to grow but now has lower numbers from the savage eating that the heterotrophs put on them so it takes a while to catch back up... then it will start to consume the N sources like you are expecting.

I cannot make this model work without affecting ammonia and nitrate levels in the aquarium at the same time. I still like it. So let me tinker with it.

I can make your idea work with a different mechanism. If I assume that time is required for a bacteria community to develop that consumes nitrate. So, dosing drives a community development that eliminates nitrate. When dosing stops, this community falls apart to be replaced by other communities. The suddenness of nitrate disappearance reflects the exponential growth of this community when acetate or ethanol concentration are high enough. I think this idea is supported by the observation that the bacteria floc and slime produced by dosing quickly disappear upon nitrate depletion.

 

[Randy Holmes-Farley Verified Community Expert]

Since we can DNA test for bacteria strains, I wonder how far off we are from having their personal lunch schedules?

Out of curiosity..

On using bacteria for nitrogen compound removal: Anyone notice if a higher hydrogen or oxygen to carbon ratio performed better? Or a higher carbon ratio to hydrogen/oxygen? Does the ratio even matter?

Some examples..
Ethenol= C2 H4 O
Acetic Acid= C2 H4 O2
Ascorbic Acid= C6 H8 O6
Alginic Acid= C6 H8 O6
Glucose= C6 H12 O6
..to the bigger..
HPMC= C56 H108 O30
Tannic Acid= C76 H52 O46

I know terrestrial plants can use tannin (like the poplar tree) but not cellulose (like HPMC). Hmm..

This conversation is above my head honestly.

There’s no general simplistic rule about what can and cannot be metabolized, but overall, the more H and less O per C, the more energy is available by converting it to CO2.

 

[jda]

I cannot make this model work without affecting ammonia and nitrate levels in the aquarium at the same time. I still like it. So let me tinker with it.

I can make your idea work with a different mechanism. If I assume that time is required for a bacteria community to develop that consumes nitrate. So, dosing drives a community development that eliminates nitrate. When dosing stops, this community falls apart to be replaced by other communities. The suddenness of nitrate disappearance reflects the exponential growth of this community when acetate or ethanol concentration are high enough. I think this idea is supported by the observation that the bacteria floc and slime produced by dosing quickly disappear upon nitrate depletion.

It is also possible, and even likely, that any growing bacteria could be getting their N from nh4 and no2 and the no3 drop is from anoxic bacteria (or other things more willing to use no3) where less no3 is being produced.. Do not assume that anything new has to use no3 for it to drop - even the same no3 use in the tank will drop no3 if nh4 and no2 is getting consumed at a higher rate. I probably rambled, so my apologies if this is jibberish.

 

[taricha]

Thinking about how to refine the question a bit...
Here's some things that are technically solutions to my question but are actually not helpful at all.
Cellulose: clearly not a usable energy source for algae, but bacteria can break it down - slowly, partially, under the right conditions.
Here's a hobby product that's not too far removed from that idea:
"Composed of an all-natural chitin substrate that mimics copepod exoskeleton fragments and coated with PNSB, Hydrospace™ PNS YelloSno™ effectively simulates a marine snowfall."

also Formate is of low digestibility to most things, but bacteria can be grown to scale up to the challenge - (one would conclude, given the long time that it takes to ramp up All For Reef.)

but I think neither of those could really be used to grow bacterial populations the way we think of for "Carbon dosing."

 

[taricha]

There’s no general simplistic rule about what can and cannot be metabolized, but overall, the more H and less O per C, the more energy is available by converting it to CO2.

Thanks, that's a useful simplification and helps with context for things like....

Ethenol= C2 H4 O
Acetic Acid= C2 H4 O2

....ethanol being higher energy than acetic acid demonstrated by the fact some bacteria can oxidize ethanol to acetic acid.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, ethanol isCH3CH2OH, so C2H6O. That quote. says ethenol, which is a different molecule, CH2=CHOH.

Ethenol aka vinyl alcohol is an unstable
molecule.