Theory on nutrient ratios and algae/bacteria

[MnFish1]

My apologies for letting this thread lapse. I've had a very rough few days at work.


@MnFish1 If you continue with posts that add value to the thread, I have no issues with you continuing to post. My issue is when you use No True Scotsman arguments like saying studies of cyano in estuaries doesn't apply to marine environments despite the study being quoted specifically stated that the studied cyano strains were identical to those found in the ocean. Or using a Straw Man argument like saying that the CNP ratio of bacteria shouldn't be considered valid because it can't also be used to study the nutritional intake of an elephant.

You are more than welcome to continue posting if you do so in a manner that adds value.

In all honesty - I thought your post calling me a 'troll' was un-called for', insulting and inappropriate. Thats just my feelings - and my feelings were hurt by the comment you made. I'm not going to respond to the rest except to quote the sentence which you took totally out of context above. I said this: Could you total the CNP ratio of an elephant and decide what to feed it as compared to the CNP ratio of a salamander? (the answer is of course it could not) - it was a joke.

Hope your next work-week goes better.

 

[BigJohnny]

I would think it would have to be very intense to have a effect on Cyanobacteria in that way. If we are talking lighting above a DT. It would have to emit UV-B, UV-A. If there was such a lighting system, it would be all that good for coral.

I was more thinking of a UV sterilizer/water clarifier’s effect on bacteria in the water column.

Pretty sure reefbrite came out with actually uv led bars. Not sure if uv-a or uv-b, but I agree, much more relevant to a powerful concentrated situation like a uv sterilizer.

 

[MnFish1]

So - can I ask a question - to @Lasse or @Brew12 or anyone. Without going through the rest of the discussion which kind of went off track. Do you think that if you total up the number of C N and P atoms in an organism, that you can predict what the proper ratio of nutrients is to keep them either thriving or to limit them? (as was suggested in the original post). If you can use these ratios, to what degree are they effective, I,e, do the effects of flow, oxygen, light, other elements, substrate overrule them? This is different than saying that different nitrate and phosphorous concentrations can affect various phytoplankton and cyanobacteria. (which is how imho, the original post went off track).

I ask this because looking at my tank - I have a few areas of Dino's but they are all in high light areas with none anywhere else. Obviously, the N and P and other chemistries are the same in the whole tank. I have had cyanobacteria - which was easily controlled by increasing flow to that area - while the 'chemistry' in the tank stayed the same.

 

[mcarroll]

I ask this because looking at my tank - I have a few areas of Dino's but they are all in high light areas with none anywhere else.

These areas clear up after lights out and return in the morning, correct?

One of the reasons dino's "snot up" is for protection from bright light. Very likely they are around other places too, but they only form visible snot mats in the light areas.

Obviously, the N and P and other chemistries are the same in the whole tank.

"The obvious" is sometimes a great place to hide things.

You may be surprised at how heterogenous the "nutrient-topography" is in your tank.

Natural eddies in the flow of your tank will concentrate detritus in some areas and not others, just for one example. Livestock and other factors also play into this too. If there's already a coral under that eddie, then you get bigger corals instead of cyano mats. THAT is my kind of algae control. Another example is to test the water going down the drain to be filtered and then test the filtered water being pumped up to your tank. I've seen some big differences between the two samples, but hardly anyone tests like that. To at least some extent, the whole tank is under that gradient of "low nutrient" water coming up from the sump and the "high nutrient" water going down the drain.

 

[MnFish1]

These areas clear up after lights out and return in the morning, correct?

One of the reasons dino's "snot up" is for protection from bright light. Very likely they are around other places too, but they only form visible snot mats in the light areas.



"The obvious" is sometimes a great place to hide things.

You may be surprised at how heterogenous the "nutrient-topography" is in your tank.

Natural eddies in the flow of your tank will concentrate detritus in some areas and not others, just for one example. Livestock and other factors also play into this too. If there's already a coral under that eddie, then you get bigger corals instead of cyano mats. THAT is my kind of algae control. Another example is to test the water going down the drain to be filtered and then test the filtered water being pumped up to your tank. I've seen some big differences between the two samples, but hardly anyone tests like that. To at least some extent, the whole tank is under that gradient of "low nutrient" water coming up from the sump and the "high nutrient" water going down the drain.

Yes - I agree - the other point I meant to mention was that it seems to me like the biggest issue is the 'local' nutrient levels in parts of the tank that certain things seem to favor. I will have to check on the lights on off thing. I also thing the best way to limit some of these 'nuisance' organisms is to have more 'desirable' organsms (i.e. corals)

 

[Brew12]

So - can I ask a question - to @Lasse or @Brew12 or anyone. Do you think that if you total up the number of C N and P atoms in an organism, that you can predict what the proper ratio of nutrients is to keep them either thriving or to limit them?

I suggest going back and reading some of the linked studies. They discuss the uptake requirements of different organisms. As the studies do point out, if you understand the waste products generated by the organisms, and you know their content, you can calculate their intake.

If you can use these ratios, to what degree are they effective, I,e, do the effects of flow, oxygen, light, other elements, substrate overrule them?

These aren't contradictory or overruling. High flow can strip phosphates off of rock that may be leaching it. Bright light may be needed to support the chemistry to process nutrients. Other trace elements, such as sulfur may be needed.

Obviously, the N and P and other chemistries are the same in the whole tank. I have had cyanobacteria - which was easily controlled by increasing flow to that area - while the 'chemistry' in the tank stayed the same.

This is not the case. N and P are very non-uniform. This is exactly why I don't advocate using water testing to determine nutrient balance or deficiencies. Water chemistry gives you a snap shot (and an inaccurate one at that) of some nutrients in the water. It doesn't tell you the nutrient level in your sand bad. Or if you have a section of rock leaching phosphates. You will also get different readings in the morning than at night.

This is why I never mentioned acting only on water test results. I believe we can use the visual symptoms of different bacteria with an understanding of their nutrient requirements to come up with a possible treatment plan.

 

[Brew12]

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[MnFish1]

I suggest going back and reading some of the linked studies. They discuss the uptake requirements of different organisms. As the studies do point out, if you understand the waste products generated by the organisms, and you know their content, you can calculate their intake.

You didn't answer my question - which was - Do you think that if you total up the number of C N and P atoms in an organism, that you can predict what the proper ratio of nutrients is to keep them either thriving or to limit them? I did not see a study that referenced the CNP ratio of a specific organism as being able to predict their nutrient requirements.

These aren't contradictory or overruling. High flow can strip phosphates off of rock that may be leaching it. Bright light may be needed to support the chemistry to process nutrients. Other trace elements, such as sulfur may be needed.

I dont understand your wording. Firstly, I never said contradicted - I dont know what you mean. Secondly, by overruling, I dd not mean 'debunking the theory'. I meant overruling the effects of the nutrients. There are tanks - for example - that havre perfect conditions from a nutrient standpoint for a certain bacteria to grow - yet they do not because some other factor prevents it.

This is not the case. N and P are very non-uniform. This is exactly why I don't advocate using water testing to determine nutrient balance or deficiencies. Water chemistry gives you a snap shot (and an inaccurate one at that) of some nutrients in the water. It doesn't tell you the nutrient level in your sand bad. Or if you have a section of rock leaching phosphates. You will also get different readings in the morning than at night. This is why I never mentioned acting only on water test results. I believe we can use the visual symptoms of different bacteria with an understanding of their nutrient requirements to come up with a possible treatment plan.

That was my point - that though the NP in the 'water' circulating in the tank has the same N/P except rare areas of the tank with poor flow,- there must be other factors. locally in some spots in the tank. Im just trying to get back to the original post when you recommended dosing po4. and nitrate - for different bacteria because of the CNP ratio but now you say you dont test for them. unless I completely missed your point.

 

[Brew12]

You didn't answer my question - which was - Do you think that if you total up the number of C N and P atoms in an organism, that you can predict what the proper ratio of nutrients is to keep them either thriving or to limit them? I did not see a study that referenced the CNP ratio of a specific organism as being able to predict their nutrient requirements.

I did answer your question. I may not have done it in a manner you understood. An organism cannot be made up of nutrients it hasn't consumed. Maybe I'm not sure what you are asking if that isn't getting to the point.

I dont understand your wording. Firstly, I never said contradicted - I dont know what you mean. Secondly, by overruling, I dd not mean 'debunking the theory'. I meant overruling the effects of the nutrients. There are tanks - for example - that havre perfect conditions from a nutrient standpoint for a certain bacteria to grow - yet they do not because some other factor prevents it.

I was speaking in terms of being contradictory or overruling in terms of their needing them for reproduction or growth. For instance, many dino's need light. If you remove the light it doesn't matter what nutrients are in the tank. Not having light isn't overruling the nutrients and it isn't contradictory in saying that the nutrients aren't required. In this case, it takes both in a complimentary manner.

That was my point - that though the NP in the 'water' circulating in the tank has the same N/P except rare areas of the tank with poor flow,- there must be other factors. locally in some spots in the tank. Im just trying to get back to the original post when you recommended dosing po4. and nitrate - for different bacteria because of the CNP ratio but now you say you dont test for them. unless I completely missed your point.

What I suggested in my first post is that if you see cyano or dino's in your system then it is worth testing your water to see if you are nutrient limited. For instance, if you have cyano and you have no NO3 in your water you can start by going down one of 2 paths. Either add NO3 or reduce PO4. Why? Because the most abundant strains of cyano don't need much NO3. As one of the studies I linked pointed out, phytoplankton will outcompete most cyano strains as long as it isn't nutrient/light limited. Its the first step I always recommend as a chemical free solution to getting rid of cyano. It doesn't always work but it does work quite frequently.


For anecdotal evidence, take a look at the Vibrant thread. It is a VERY long read, but there are dozens, maybe hundreds, of cases of cyano that were caused by low NO3 from the carbon dosing involved with Vibrant. The majority of them were cleared up in days by adding NO3.

 

[MnFish1]

I did answer your question. I may not have done it in a manner you understood. An organism cannot be made up of nutrients it hasn't consumed. Maybe I'm not sure what you are asking if that isn't getting to the point.

It was a yes or no question. More specifically, Do you believe that you can predict what will make an organism thrive or not by drying it out and measuring C N and P and feeding a ratio based on that (Or providing water somehow using that information. My answer to that questions is 'no'. Im assuming your answer is yes.

I was speaking in terms of being contradictory or overruling in terms of their needing them for reproduction or growth. For instance, many dino's need light. If you remove the light it doesn't matter what nutrients are in the tank. Not having light isn't overruling the nutrients and it isn't contradictory in saying that the nutrients aren't required. In this case, it takes both in a complimentary manner.

Not having light is absolutely over-ruling the nutrients in this case. Thats the point. If you remove the light it doesn't matter what nutrients are in the tank - on a continuum then - as are many things in nature - I was implying that though nutrients play a role - but Im not sure anyone has proven how important - or manageable that role is in the aquarium.

What I suggested in my first post is that if you see cyano or dino's in your system then it is worth testing your water to see if you are nutrient limited. For instance, if you have cyano and you have no NO3 in your water you can start by going down one of 2 paths. Either add NO3 or reduce PO4. Why? Because the most abundant strains of cyano don't need much NO3. As one of the studies I linked pointed out, phytoplankton will outcompete most cyano strains as long as it isn't nutrient/light limited. Its the first step I always recommend as a chemical free solution to getting rid of cyano. It doesn't always work but it does work quite frequently.

OK - but in your last post you stated that water tests are basically useless - because of local conditions. Again im not trying to start an argument - but how much role does the fact that the 'water' is nitrate or PO4 limited - if there are local areas that are not all over the tank - and once you start dosing NO3 and PO4. unless you are testing how do you know how much to add.

Thanks for answering

 

[Brew12]

It was a yes or no question. More specifically, Do you believe that you can predict what will make an organism thrive or not by drying it out and measuring C N and P and feeding a ratio based on that (Or providing water somehow using that information. My answer to that questions is 'no'. Im assuming your answer is yes.

I believe that useful information can be obtained. Can you explain why you believe their is no tie between what nutrients an organism consumes and its chemical makeup?

Not having light is absolutely over-ruling the nutrients in this case. Thats the point. If you remove the light it doesn't matter what nutrients are in the tank - on a continuum then - as are many things in nature - I was implying that though nutrients play a role - but Im not sure anyone has proven how important - or manageable that role is in the aquarium.

I think you are playing word games. Call it over ruling if you would like. My point is that it takes both. Neither is more important than the other.

OK - but in your last post you stated that water tests are basically useless - because of local conditions. Again im not trying to start an argument - but how much role does the fact that the 'water' is nitrate or PO4 limited - if there are local areas that are not all over the tank - and once you start dosing NO3 and PO4. unless you are testing how do you know how much to add.

I'm curious, do you do any testing in your aquarium? If so, why?

 

[MnFish1]

I believe that useful information can be obtained. Can you explain why you believe their is no tie between what nutrients an organism consumes and its chemical makeup?


I think you are playing word games. Call it over ruling if you would like. My point is that it takes both. Neither is more important than the other.


I'm curious, do you do any testing in your aquarium? If so, why?

Sorry I cant get the multi quote to work - so ill just answer 1, 2, 3

1.
Because - especially single celled/simple organisms contain mostly the same stuff.. 'DNA'. 'RNA' various proteins that are all similar. I read one study that suggested the main difference in the CNP ratios was amounts of RNA - but don't quote me on that. Bacteria are less complex than plankton but they still have the same basic 'equipment'. Every living cell contains C N and P. Because the basic building blocks of life are made of this - (and O, etc). Cyanobacteria and some of the others have evolved to live in LOTS of conditions - and they do. Which is why there are so many opinions on what to do about them.

I also did not say there was 'no tie' between what nutrients an organism consumes and its chemical makeup. I said that I disagreed with your premise that altering chemicals in the water is a major factor in controlling these types of 'pests' in the aquarium. I stated (and I agreed with you - on the refugium/iron issue) that out competition with more corals, etc - is a better way. Taking aside the old adage 'you are whaat you eat', here is an example. Lets say you took a dinoflagellate - and did a CNP ratio. Well - they can get nutrition from the water, from things they consume (i..e other bacteria, and etc) depending on what conditions are present. There are so many variables that it becomes hard to control all of them.

Another Analogy - which may or may not be appropriate - but its only an analogy - and it ticked you off the last time - but I think its somewhat valid. If you analyzed the CNP ratio of an elephant and a salamander - could you tell what the best diet on which they would thrive.?


2.
I humbly disagree (I wasnt trying to play word games - and I never used the word contradicting). I used a black and white example (no pun intended) - of no light - no dinos, but - but there is always a continuum. there is no way to tell whether one is more important than another as the level of one goes up - and the other goes down. Its my opinion that nutrients (in the water column) are less important than local influences light and flow.

3.
I find nitrate and phosphate testing problematic - because the results mean different things depending on the tank. I never know what to do with the results. Because - for the most part - unless there is a problem in the tank (a sudden dead fish, etc) - there is a balance that results in a low PO4 and Nitrate - even in tanks that have tons of algae that look horrible. I.e. a tank with a high Nitrate or phosphate has a problem (overfeeding/poor export/poor filtration, etc etc)

So - I test it periodically - with various test kits - to verify - when I think something is off. My nitrate is never 'high' and my PO4 is always 'ok' - but I dont make huge changes to my tank that would sway whatever balance the tank is in.

I test CA and Alkalinity weekly - though focus more on alkalinity. mostly because I have a touchy dosing pump - and when my goniopra starts to look weird - I check it lol - its usually that the dosing pump has messed up and the alk is low.

Im not a believer in ICP testing - but perhaps that will be an issue later. At this point I think its more voodoo than science.

 

[Brew12]

Another Analogy - which may or may not be appropriate - but its only an analogy - and it ****** you off the last time - but I think its somewhat valid. If you analyzed the CNP ratio of an elephant and a salamander - could you tell what the best diet on which they would thrive.?

The difference is that several of the studies I have linked show a direct connection between the nutrients consumed and the chemical content of the organisms. Trying to compare a complex organism to a single cell organism isn't useful. Two of the studies I linked show that the nutrients consumed by phytoplankton almost exactly match the chemical composition of a mass of phytoplankton. They are almost exactly what they eat. One of the studies I linked about estuary cyanobacteria came to an identical conclusion.

There are outliers, such as nitrifying bacteria. They consume much more nitrate in the form of NH4 than their biomass contains. Dinoflagellates are also not as representative of what they consume. I just don't feel that it means the information across the board is useless.

Its my opinion that nutrients (in the water column) are less important than local influences light and flow.

Without phosphate there would be absolutely no life in your tank. Without light you would still have great diversity of life. I'm not saying that nutrients are more important than light. It's all about balance.

I find nitrate and phosphate testing problematic - because the results mean different things depending on the tank. I never know what to do with the results. Because - for the most part - unless there is a problem in the tank (a sudden dead fish, etc) - there is a balance that results in a low PO4 and Nitrate - even in tanks that have tons of algae that look horrible. I.e. a tank with a high Nitrate or phosphate has a problem (overfeeding/poor export/poor filtration, etc etc)

I agree with the testing being problematic yet almost all of us do it. Trying to figure out how to apply what we see in our tests and relate it to the symptoms in our tank is the main focus of what I am striving for.

I think ICP testing is just one more tool that we can use. I feel some of the accuracies are overstated but there may be value even if we don't always understand what it is telling us.

 

[MnFish1]

The difference is that several of the studies I have linked show a direct connection between the nutrients consumed and the chemical content of the Trying to compare a complex organism to a single cell organism isn't useful. Two of the studies I linked show that the nutrients consumed by phytoplankton almost exactly match the chemical composition of a mass of phytoplankton. They are almost exactly what they eat. One of the studies I linked about estuary cyanobacteria came to an identical conclusion.

There are outliers, such as nitrifying bacteria. They consume much more nitrate in the form of NH4 than their biomass contains. Dinoflagellates are also not as representative of what they consume. I just don't feel that it means the information across the board is useless.

Without phosphate there would be absolutely no life in your tank. Without light you would still have great diversity of life. I'm not saying that nutrients are more important than light. It's all about balance.


I agree with the testing being problematic yet almost all of us do it. Trying to figure out how to apply what we see in our tests and relate it to the symptoms in our tank is the main focus of what I am striving for.

I think ICP testing is just one more tool that we can use. I feel some of the accuracies are overstated but there may be value even if we don't always understand what it is telling us.

If it’s not too much trouble would you mind sending me the text from one of the studies that ‘show a direct connection between the nutrients consumed and the chemical content of the organism. ‘. It’s my understanding that Dino’s for example eat bacteria and other smaller things as well as taking up stuff from the water column

 

[Brew12]

If it’s not too much trouble would you mind sending me the text from one of the studies that ‘show a direct connection between the nutrients consumed and the chemical content of the organism. ‘. It’s my understanding that Dino’s for example eat bacteria and other smaller things as well as taking up stuff from the water column

This isn't the best one I had come across, but it does make the point.

http://www.tandfonline.com/doi/pdf/10.1017/S0967026201003456

"The physiological plasticity of phytoplankton and the phenomenon of luxury consumption allow inorganic N and P levels to be stripped to undetectable concentrations in nutrient-limited cultures of widely varying inorganic N and P contents (Goldman et al., 1979). The N of extremely nutrient-limited phytoplankton cells equalled the N originally present in the medium over a range of nitratehosphate ratios from !5 to"50 (Rhee, 1974; Goldman et al., 1979; Elrifi & Turpin, 1985). The ability of phytoplankton to strip inorganic nutrients to undetectable levels in chemostat cultures depends on the dilution rate (i.e. growth rate). The range of N is more restricted at higher dilution rates (¯higher growth rates) (Goldman et al., 1979)."

I'll send you a better study on Monday that I have saved on my computer at work. It goes into much more detail, including how most frozen and prepared marine aquarium foods have a very similar ratio since phytoplankton is the base of the food chain.

 

[ksed]

Following along

 

[Brew12]

If it’s not too much trouble would you mind sending me the text from one of the studies that ‘show a direct connection between the nutrients consumed and the chemical content of the organism. ‘. It’s my understanding that Dino’s for example eat bacteria and other smaller things as well as taking up stuff from the water column

Here is the better study.

http://www.int-res.com/articles/meps/8/m008p015.pdf

"The average atomic ratio for particulate matter from the stored system was 113:15:1 which is a good fit to the model (the Redfield ratio of C:N: P is 106:16:1). The concentration of particulate matter from the recirculating system was considerably lower than that from the stored system, but the average ratio of 98:14: 1 is insufficiently different from the Redfield ratio."

 

[MnFish1]

Here is the better study.

http://www.int-res.com/articles/meps/8/m008p015.pdf

"The average atomic ratio for particulate matter from the stored system was 113:15:1 which is a good fit to the model (the Redfield ratio of C:N: P is 106:16:1). The concentration of particulate matter from the recirculating system was considerably lower than that from the stored system, but the average ratio of 98:14: 1 is insufficiently different from the Redfield ratio."

Now that I understand what evidence you're using I'll try to answer your first question: I dont believe you can use the CNP ratio of an organism to predict how to help it 'thrive or decline'. I think varying nutrient levels in a given tank may be very helpful in limiting certain undesirable 'stuff' - just that the CNP ratios of the organism can not help you predict whether a given nutrient will help it thrive or decline (this was your thesis in your OP - I believe). Somehow we've gotten off the original topic so I'd like to bring this back there.

The Redfield ratio is used in the study of plankton. (not bacteria - not Cyanobacteria) so the study you quote (which focus on plankton) cannot be used to say the same the same things about 'non-harmful bacteria' or Cyanobacteria. So for a minute lets focus on phtytoplankton:

As I posted once before - Redfield himself (and this is accepted currently in marine ecology) - decided that it was the phytoplankton themselves that were influencing N P ratios in Seawater - not the other way around (which also accounts for the results in your study which showed the 2 groups were statistically insignificant):

Redfield: N P in seawater “must tend to approach that characteristic of protoplasm in general” (Redfield 1934). Furthermore, Redfield proposed thermostat like scenario in which the activities of nitrogen fixers and denitrifies keep the nitrate to phosphate ratio in the seawater near the requirements in the protoplasm. (Redfield, 1958). Redfield proposed that the ratio of Nitrogen to Phosphorus in plankton resulted in the global ocean having a remarkably similar ratio of dissolved nitrate to phosphate (16:1). He considered how the cycles of not just N and P but also C and O could interact to result in this match.

As to Bacteria and CNP (Cyano and heterotrophic). Here is 1 study abstract looking at CNP ratios in other types of 'bacteria' (i.e. not phytoplankton). "The baseline for studies of the elemental stoichiometry of marine microorganisms was established more than 60 years ago by Alfred Redfield, who estimated that marine plankton (and organic marine detritus) have a carbon/nitrogen/phosphorus (C/N/P) ratio of 106/16/1 (BNID 112423). The Redfield ratio remains the foundation for studies of the elemental composition of marine microorganisms and organic matter, particularly in the deep oceans [refs 4,15]. Indeed, the observed elemental ratios can vary greatly with the component of marine organic biomass that is under consideration: for example, estimates of C/N/P for marine heterotrophic bacteria are reported to be around 69/16/1 (primary source 5), and measurements for individual cyanobacterial isolates include 46/10/1 (for Prochlorococcus sp. MED4 under phosphorus‑replete conditions) and 301/49/1 (for Synechococcus sp. WH8013 under phosphorus‑limited conditions) (primary source 12). Thus, the elemental stoichiometry of bacterial cells varies with taxa and growth conditions and often differs substantially from the Redfield ratio (reviewed in ref. 16)."

The numbers in that study are quite different than the numbers in your OP - (Non harmful marine bacteria with a typical N: P ratio of 50:1), Cyanobacteria has a N: P ratio of between 1:1 and 5:1) In their study - heterotrophic bacteria were 16:1 and Cyanobacteria 10:1 and 49:1 (depending on phosphate concentration). As you said - dinoflagellates are 'all over the map'.

Based on what I've read - certain NP ratios (in the water) can enhance or inhibit certain strains of microorganisms. However, the NP ratio of the organism itself cannot be used to predict the concentrations to use to inhibit or enhance it. Use the example of the cyanobacteria in the study above - in phosphorous depleted conditions - the NP ratio was 50:1. In phosphorous replete conditions the NP ratio was 10:1 (though they are different species as well). However - organisms also have mechanisms for storing elements for when conditions are 'lean' - so an organism may have an overabundance of an element simply because there is more of that element at that moment.

 

[Brew12]

Now that I understand what evidence you're using I'll try to answer your first question: I dont believe you can use the CNP ratio of an organism to predict how to help it 'thrive or decline'.

Actually, these aren't the studies I was using for that purpose. Only part of the bigger picture. They were specifically in response to this question.

would you mind sending me the text from one of the studies that ‘show a direct connection between the nutrients consumed and the chemical content of the organism.

That is what these studies showed. Please stop twisting arguments around to "prove" something completely out of context.

 

[MnFish1]

Actually, these aren't the studies I was using for that purpose. Only part of the bigger picture. They were specifically in response to this question. That is what these studies showed. Please stop twisting arguments around to "prove" something completely out of context.

You're correct - but I wasn't twisting facts - I asked you for a study - gave it to me - l liked the post. When I said evidence in my answer to you I wasn't referring to ONLY that study I was referring to ALL of the studies you've posted - I should have started out by saying I do not think those studies prove your point in your OP (either).

I do find it humorous that you pick on one small item of a longer post which I think has valid points about your thesis - you dont respond to those - instead you pick some other things to ask about. You seem to do that often - answering a question with another question which tends to bring the thread onto another topic only minimally related to the original post...

The proof that one cannot use CNP ratios alone as you have tried to do is simple - Organisms, whether humans (individual human cells), or bacteria, store elements when they are plentiful *(up to a point) so they can be used when they are not plentiful. Thus, measuring the elemental composition and performing a ratio may not mean the same depending on the conditions in which the organism grew. In other words, you're correct when you say 'organisms can only contain what they have taken in' - but they may have taken in more than they need....

Secondly - the overlap of the numbers in your OP and published data minimize (to me) the usefulness of CNP ratios in deciding what to do in an aquarium ie nitrate/po4 dosing.