“Balance! Daniel son“ phosphate vs nitrate

[Randy Holmes-Farley]

I'm not quibbling I'm just asking. It never made any sense to me but I've heard some reefers swear by the "divide by 16" rule.

IMO, that’s a flawed way of thinking.

Never is it better to set targets by ratios than by absolute values, and ratios frequently make very poor predictions (if one is very low or very high, is it ever appropriate for the other one to also be very low or high?). IMO, no.

 

[Randy Holmes-Farley]

I'm asking does the redfield ratio mean ANYTHING to us as hobbyists? Or is it just more noise. I don't do academic exercises, Randy. I barely do psychical exercise. You'd smoke me at reef tank jeopardy.

while it provides info as to what ratios some types of organisms consume, and to the ratio usually found in the ocean, it does not provide guidance for setting targets and was never intended that way.

 

[BanjoBandito]

while it provides info as to what ratios some types of organisms consume, and to the ratio usually found in the ocean, it does not provide guidance for setting targets and was never intended that way.

I'm trying not to hijack this thread, but I hear MANY people use it to determine how carbon dosing works - is that accurate or more smoke?

 

[ReefGeezer]

I'm not quibbling I'm just asking. It never made any sense to me but I've heard some reefers swear by the "divide by 16" rule.

Sorry for the quibbling remark. There has been so much noise about Redfields for so many years. I guess I just get a little wound up about it sometimes. I think it causes people to start chasing numbers rather than understanding how nutrients are processed in a system.

 

[BanjoBandito]

Sorry for the quibbling remark. There has been so much noise about Redfields for so many years. I guess I just get a little wound up about it sometimes. I think it causes people to start chasing numbers rather than understanding how nutrients are processed in a system.

I get it, hard to prove intent online. I am certainly no number chaser....honestly this forum makes me get weird about my phosphate numbers and then I have to slap myself out of it. lol.

 

[sixty_reefer]

Nope. I am a hobbyist not a biologist. I have performed no studies or written peer reviewed papers about the subject. I rely on the my understanding of the subject and my interpretation of the consensus on the subject and apply it to my tank.

To expound on my opinion on this subject... I know that C, N, and P are required for life. I know that C, N, and P exist in my tank in many forms. I know that I can't test for all the forms. It is my opinion that different organisms use different forms of C, N, and P. It is my opinion that in a properly operating system that C, N, and P in all of its forms is processed in interrelated loops determined in large part by the organisms present and not a set ratio.

Thank you, for the clarification

 

[ReefGeezer]

I get it, hard to prove intent online. I am certainly no number chaser....honestly this forum makes me get weird about my phosphate numbers and then I have to slap myself out of it. lol.

Yep... me too.

 

[Randy Holmes-Farley]

I'm trying not to hijack this thread, but I hear MANY people use it to determine how carbon dosing works - is that accurate or more smoke?

It’s misguided, IMO.

There’s no reason to assume that N and P are consumed in any specific ratio when carbon dosing because it can drive processes that use both N and P (tissue building) and also can drive denitrification that uses N (as nitrate) and not P.

 

[ReefGeezer]

It’s misguided, IMO.

There’s no reason to assume that N and P are consumed in any specific ratio when carbon dosing because it can drive processes that use both N and P (tissue building) and also can drive denitrification that uses N (as nitrate) and not P.

Sorry for the hjack... Hey Randy. I didn't know carbon dosing could drive denitrification. That would explain some things. Would you please tell me how that works? Thanks Randy.

 

[Randy Holmes-Farley]

Sorry for the hjack... Hey Randy. I didn't know carbon dosing could drive denitrification. That would explain some things. Would you please tell me how that works? Thanks Randy.

Sure, it provides organics for the process described below:

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

Deep sand beds can develop low oxygen regions where nitrate is used by bacteria. They use it to metabolize organics that randomly diffuse into the sand from the water column. When the oxygen gets depleted in the sand, the bacteria can still oxidize the organics available by using nitrate instead of O2. In this situation, nitrate acts as an electron acceptor (e.g., an oxygen source) in place of oxygen (O2). The end result is that nitrate is converted into N2, and the N2 blows off of the tank to the atmosphere. The reactions that take place can be complex.22 In oxygen-containing environments, the reaction looks very similar to that shown above for plankton (ignoring phosphorus here):

organic + 175 O2 → 122 CO2 + 16 NO3– + 16 H+ + 138 H2O

where organic stands for a typical organic material ((CH2O)80(CH2)42(NH3)16) that is being metabolized. In the absence of O2, and taking the nitrogen species completely to N2 (which may happen in several reaction steps), we have the following overall reaction:

organic + 124 NO3– + 124 H+ → 122 CO2 + 70 N2 + 208 H2O

It can be seen that the process above produces alkalinity (by consuming H+). In fact, it is the exact same amount of alkalinity that was depleted when the nitrate was originally formed from foods, so the net effect of the nitrogen cycle on alkalinity is zeroed out.

In many aquaria, the process takes place to an extent sufficient by itself to keep nitrate at levels below 0.5 ppm. In others, it has not been adequate. Success may depend on the size of the bed, its composition (sand type, particle size distribution, depth, and life forms in it), and the demands put on it in terms of nitrate processing. It is rarely discussed by aquarists, but organics are critical for this process as well, and some aquaria may have more or less organic matter in the water (due to use of things like skimming or granular activated carbon) and this, in turn, can impact the nitrate conversion capability of a sand bed.

This process also happens in the pores of live rock, and in a variety of other environments in a reef aquarium.

 

[Rmckoy]

Wouldn't the redfield ratio mean phosphate should be at 1.25 or am I thinking wrong or is the math wrong?

If that’s he 16:1 ratio is correct or if it applied 1.25 would be correct .
but for 20ppm nitrates , 1.25ppm phosphates is insanely high . Ideally our target is less than 1ppm

 

[sixty_reefer]

Sure, it provides organics for the process described below:

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

Deep sand beds can develop low oxygen regions where nitrate is used by bacteria. They use it to metabolize organics that randomly diffuse into the sand from the water column. When the oxygen gets depleted in the sand, the bacteria can still oxidize the organics available by using nitrate instead of O2. In this situation, nitrate acts as an electron acceptor (e.g., an oxygen source) in place of oxygen (O2). The end result is that nitrate is converted into N2, and the N2 blows off of the tank to the atmosphere. The reactions that take place can be complex.22 In oxygen-containing environments, the reaction looks very similar to that shown above for plankton (ignoring phosphorus here):

organic + 175 O2 → 122 CO2 + 16 NO3– + 16 H+ + 138 H2O

where organic stands for a typical organic material ((CH2O)80(CH2)42(NH3)16) that is being metabolized. In the absence of O2, and taking the nitrogen species completely to N2 (which may happen in several reaction steps), we have the following overall reaction:

organic + 124 NO3– + 124 H+ → 122 CO2 + 70 N2 + 208 H2O

It can be seen that the process above produces alkalinity (by consuming H+). In fact, it is the exact same amount of alkalinity that was depleted when the nitrate was originally formed from foods, so the net effect of the nitrogen cycle on alkalinity is zeroed out.

In many aquaria, the process takes place to an extent sufficient by itself to keep nitrate at levels below 0.5 ppm. In others, it has not been adequate. Success may depend on the size of the bed, its composition (sand type, particle size distribution, depth, and life forms in it), and the demands put on it in terms of nitrate processing. It is rarely discussed by aquarists, but organics are critical for this process as well, and some aquaria may have more or less organic matter in the water (due to use of things like skimming or granular activated carbon) and this, in turn, can impact the nitrate conversion capability of a sand bed.

This process also happens in the pores of live rock, and in a variety of other environments in a reef aquarium.

As I read it seems that you are describing the denitrification process by autotrophic bacteria that don’t utilise the nutrients C or P, the main bacteria in most mature reef tanks is heterotrophic bacteria that utilises C N P

 

[Randy Holmes-Farley]

As I read it seems that you are describing the denitrification process by autotrophic bacteria that don’t utilise the nutrients C or P

The article describes a number of processes, but the ones shown above are hetetotrophic metabolism of an ordinary natural organic (not exactly organic carbon dosing) and denitrification of those same organics by bacteria.

I ignored the P for this discussion that is about nitrate, but I include it in other discussions and articles.

Tissue growth always includes some P uptake regardless of the type of organism, and denitrification as a process never consumes P.

 

[ReefGeezer]

... where organic stands for a typical organic material ((CH2O)80(CH2)42(NH3)16) that is being metabolized. In the absence of O2, and taking the nitrogen species completely to N2 (which may happen in several reaction steps), we have the following overall reaction:

organic + 124 NO3– + 124 H+ → 122 CO2 + 70 N2 + 208 H2O....
This process also happens in the pores of live rock, and in a variety of other environments in a reef aquarium.

Thanks randy. I understand now. That helps explain seeing higher nitrate reduction than I would have expected. I now need to ask a really silly question... I'm almost embarrassed... but... When you say typical organic material ((CH2O)80(CH2)42(NH3)16) being metabolized, is that a complex organic compound like a hydrocarbon, lipid, amino acid or etc, or is that a water with a bunch of free carbon in it? Sorry, simple minds just need to ask simple questions!

 

[Randy Holmes-Farley]

Thanks randy. I understand now. That helps explain seeing higher nitrate reduction than I would have expected. I now need to ask a really silly question... I'm almost embarrassed... but... When you say typical organic material ((CH2O)80(CH2)42(NH3)16) being metabolized, is that a complex organic compound like a hydrocarbon, lipid, amino acid or etc, or is that a water with a bunch of free carbon in it? Sorry, simple minds just need to ask simple questions!

That formula represents the composition of phytoplankton and is where the Redfield ratio comes from. It is no individual type of molecule.

Heres a more expanded version with phosphate for aerobic breakdown:


The metabolic breakdown scheme for typical organic materials in phytoplankton1 is shown below:

(CH2O)106(NH3)16(H3PO4) + 138 O2 → 106 CO2 + 122 H2O + 19 H+ + PO4— + 16 NO3–

organic + oxygen → carbon dioxide + water + hydrogen ion + phosphate + nitrate

Which is from:

Phosphate in the Reef Aquarium

The phosphorus atom is one of living matter's basic building blocks. It is present in every living creature and in every reef aquarium's water. Unfortunately, it is often present in excess in reef aquaria, and that excess has the potential to cause at least two substantial problems for...

www.reefedition.com

 

[Dan_P]

If my nitrate is at 20 where ideally does phosphate read ?

thank you

I am pretty sure there is no such thing.

 

[ReefGeezer]

That formula represents the composition of phytoplankton and is where the Redfield ratio comes from. It is no individual type of molecule...

Thanks Randy. I'll chew on that for a while.

 

[Carl C]

Wouldn't the redfield ratio mean phosphate should be at 1.25 or am I thinking wrong or is the math wrong?

I hope not ; my LFS said that's way too high and will kill Coral

 

[Randy Holmes-Farley]

I hope not ; my LFS said that's way too high and will kill Coral

If nitrate is 25 ppm and phosphate is 2.5 ppm, that fits the Redfield ratio exactly (N : P molar ratio of 16;1).

IMO, if nitrate is 25 ppm, it would be a very poor idea to target phosphate to 2.5 ppm.

Time to say goodnight to Redfield in relation to reef target ratios.

 

[BanjoBandito]

I hope not ; my LFS said that's way too high and will kill Coral

Yeah that phos level is even too high for me! Lol.