Redfield Ratio Revisited – What are we doing wrong?

[Randy Holmes-Farley]

This was a very important insight. Previous calculariins actually worked better with the lower ratios (eg 5:1). This makes the correct ratio even more predictive.

I do not think a ratio is a useful tool in setting or evaluating target nutrient values in reef aquaria. If has obvious flaws (both N and P too low, for example) that are not present when considering the actual levels instead.

 

[DanyL]

I did not read the whole article, nor the comments so I apologize if I'm repeating something that was already mentioned, but I would like to chime in with my own view that I've never seen discussed before in relation to the redfield ratio.

My theory is that all the variations we sometimes see between systems, which do not comply with what is considered wildly acceptable levels and ratios, all originate because we are only able to see a small portion of what's really going on, and assume it would apply without considering that other, unmeasurable (at home) forms do exist and may influence the results we are expecting to see.

Both phosphate and nitrogen can be found in multiple different forms in a reef, some are bounded to rocks, sand, they can be organic, inorganic and so on and so forth.

 

[Randy Holmes-Farley]

I did not read the whole article, nor the comments so I apologize if I'm repeating something that was already mentioned, but I would like to chime in with my own view that I've never seen discussed before in relation to the redfield ratio.

My theory is that all the variations we sometimes see between systems, which do not comply with what is considered wildly acceptable levels and ratios, all originate because we are only able to see a small portion of what's really going on, and assume it would apply without considering that other, unmeasurable (at home) forms do exist and may influence the results we are expecting to see.

Both phosphate and nitrogen can be found in multiple different forms in a reef, some are bounded to rocks, sand, they can be organic, inorganic and so on and so forth.

I agree. Many organisms consume N and P at different ratios than one another, and there are many processes that use only nitrate or only phosphate,

 

[Reef and Dive]

Yeah good points.

But I still think there is good reason to extract good information out of those studies provided.

If it can be applied or not? Well show my reefs update weekly on my yt channel (years before it was not weekly, but still updated) and very often, over and over I have documented interfering with my ratios and solving problems (I just did not want to keep that for myself).
One of the examples:


Till now I think I have provided good scientific information, good reasons and tried to avoid personal interpretations. That with the addition of the practical and documented result in my reefs.

The idea is most often put aside by personal belief and no documentation or experiments. I believe some of the criticism comes from pepople that have not actually read the first post.

Anyway this is a hobby, anyone can manage their reefs how they wish without any judgment by me.

 

[Lasse]

do not think a ratio is a useful tool in setting or evaluating target nutrient values in reef aquaria. If has obvious flaws (both N and P too low, for example) that are not present when considering the actual levels instead.

I do not know if the ratio always is important - IMO this article clearly show that there is an important ratio when PO₄³⁻ concentration is low - around 0.18-0.3 µM PO₄³⁻ it correspond to around 0.18*95 to 0.3*95 -> 17.1 - 28.5 µ gr/L -> 0.017 - 0.03 mg/L PO4

Both phosphate and nitrogen can be found in multiple different forms in a reef, some are bounded to rocks, sand, they can be organic, inorganic and so on and so forth.

Yes - but we are only interested of inorganic components active in the Photosynthesis here - it leaves os with only one P species - the orthophosphate ion PO₄³⁻ - but on the other hand there is at least two inorganic species of N - NO3 and NH4 is active in the photosynthesis. Rocks and sand can be reservoir for PO₄³⁻ but if you run a prolonged period with 0 or very low PO₄³⁻ in the water column - you will sooner or later run zero even in the bound PO4.

Sincerely Lasse

 

[Randy Holmes-Farley]

I do not know if the ratio always is important - IMO this article clearly show that there is an important ratio when PO₄³⁻ concentration is low - around 0.18-0.3 µM PO₄³⁻ it correspond to around 0.18*95 to 0.3*95 -> 17.1 - 28.5 µ gr/L -> 0.017 - 0.03 mg/L PO4



Yes - but we are only interested of inorganic components active in the Photosynthesis here - it leaves os with only one P species - the orthophosphate ion PO₄³⁻ - but on the other hand there is at least two inorganic species of N - NO3 and NH4 is active in the photosynthesis. Rocks and sand can be reservoir for PO₄³⁻ but if you run a prolonged period with 0 or very low PO₄³⁻ in the water column - you will sooner or later run zero even in the bound PO4.

Sincerely Lasse

I don’t agree. Ratio defenders look for and find a case where it can be useful and neglect those cases where the same ratio at different absolute values would have a different effect.

Why not just look at the absolute values as a target for nutrients?

Ratios can sometimes give false impressions of reality, while absolute values do not.

If N or P are outside of optimal levels, might the actual value of the other make things worse? Sure. That is the context of that article.

The article talks about phosphate starvation at levels below 0.03 ppm. Many reefers would have agreed with that based on their own Reefing experience.

 

[Reef and Dive]

Why not just look at the absolute values as a target for nutrients?

Pretty simple. Because it works. Or there is any other reason why I’ve beated cyano many times dosing nitrates that I’m not aware of.

 

[Lasse]

The article talks about phosphate starvation at levels below 0.03 ppm. Many reefers would have agreed with that based on their own Reefing experience.

Yes - but there is still people that favour lower phosphate than that - and IMO this article shows that it can work - if you not exceed a ratio of 22 atoms N to 1 atom P which correspond to around 0.4 mg/L NO3 - however - if you chose to have higher PO4 than 0.03 mg/L - let us say 0.095 mg/L (= 1 µM) - you can have at least 1.36 mg/ L NO3 att an atom ratio of 22:1 N/P and the author stress that the quota seems not be so important as at levels over 0.03 - you can have a higher ratio.

I have my own ideas why a NO3 concentration of around 2 mg/L is important in order to hinder cyanobacteria to take over and it has nothing to do with ratio except that if you want a NO3 concentration between 2 - 5 ppm - you can´t have too low PO4

Sincerely Lasse

 

[Randy Holmes-Farley]

Pretty simple. Because it works. Or there is any other reason why I’ve beated cyano many times dosing nitrates that I’m not aware of.

Lol
Prove a ratio is what fixed it, as opposed to a bad absolute level of nitrate.

 

[Reef and Dive]

Lol
Prove a ratio is what fixed it, as opposed to a bad absolute level of nitrate.

50 nitrate, 0.5 phosphate = low risk of cyano

1 nitrate, 0.3 phosphate = high risk of cyano

0 nitrate 0.08 phosphate = high risk of cyano (great insight on conditions and best option to dose nitrate - why would dosing nitrate “reduce” something that consumes nitrate? Great insight from understanding conditions)

5 nitrate 0.5 phosphate = low risk of cyano, great insight for avoiding a reduction by carbon dosing. In this case it will reduce both but will shift from a low risk of cyano to a high risk of cyano environment.

Any low risk condition and plenty of cyano on a single rock and water levels do not explain cyano, so most probably this rock has plenty of “bound phosphate”, a much better explanation = solution: remove this rock.

Understanding ratios help understand most of these conditions and not a specific value. Of course I dismiss the “I have low risk case X and have cyano” and the opposite. It is all about risk and not about certainty (many non smokers have lung cancer and many people live a long life smoking - that’s just biology itself and not any particular feature of our hobby).

All these situations are pretty common. I’ve demonstrated most in practical terms in my reefs. In the past I have even changed the conditions to a worse scenario just to fix later and demonstrate and prove a point - now I just don’t do it anymore.

Reducing cyano in different scenarios can be done dosing nitrates; using GFO in other conditions; reducing food in others; and just removing a rock in others.

Actually, I don’t think cyano is a great problem and most of the time I just do nothing at all.

 

[Randy Holmes-Farley]

50 nitrate, 0.5 phosphate = low risk of cyano

1 nitrate, 0.3 phosphate = high risk of cyano

0 nitrate 0.08 phosphate = high risk of cyano (great insight on conditions and best option to dose nitrate - why would dosing nitrate “reduce” something that consumes nitrate? Great insight from understanding conditions)

5 nitrate 0.5 phosphate = low risk of cyano, great insight for avoiding a reduction by carbon dosing. In this case it will reduce both but will shift from a low risk of cyano to a high risk of cyano environment.

Any low risk condition and plenty of cyano on a single rock and water levels do not explain cyano, so most probably this rock has plenty of “bound phosphate”, a much better explanation = solution: remove this rock.

Understanding ratios help understand most of these conditions and not a specific value. Of course I dismiss the “I have low risk case X and have cyano” and the opposite. It is all about risk and not about certainty (many non smokers have lung cancer and many people live a long life smoking - that’s just biology itself and not any particular feature of our hobby).

All these situations are pretty common. I’ve demonstrated most in practical terms in my reefs. In the past I have even changed the conditions to a worse scenario just to fix later and demonstrate and prove a point - now I just don’t do it anymore.

Reducing cyano in different scenarios can be done dosing nitrates; using GFO in other conditions; reducing food in others; and just removing a rock in others.

Actually, I don’t think cyano is a great problem and most of the time I just do nothing at all.

You are making assertions, but provide no evidence to back it up. What reason do you have to make it? I do see reasons to reject it, since plenty of people have cyano under your ratios where you say it is unlikely.

In your case, where you dosed nitrate and cyano declined, do you think GFO to reduce phosphate would have had the same effect to reduce cyano?

 

[PBar]

Hello,
the issue of ratios indeed is that it should work in both ways…
Side remark, I saw the video and, if I understand correctly, everything happens in a very short period of time - week: including dosing nitrate, water change, syphoning the substrate, cyano back…
And at the end, the result is not much different from a typical cyano case in mature system.

The main point would be indeed (as Randy raised) - reducing phosphate would also bring the same outcome?

We can play around: increasing both (one more than the other) or decreasing both (one more than the other) would also need to deliver the same outcome in that sense...

I like the topic of ratios… it is a good discussion, but it is really tricky.

Note: imagine if we start to consider also the error range from the hobby tests… then more fun math starts with ratios

 

[Randy Holmes-Farley]

Note: imagine if we start to consider also the error range from the hobby tests… then more fun math starts with ratios

Imagine too if we are looking at many different species of cyano, dinos, diatoms, etc.

I saw an estimate that there are about 2,000 known species of cyano alone.

There’s no reason to think they all have identical nutrient concentration requirements.

 

[sixty_reefer]

It is not rocket science actually and pretty easy to understand. Since cyano is very efficient to uptake nitrogen from the air (diazotrophy) it simply gets and advantage when nitrogen is limited in relation to phosphate. It helps understand favourable conditions and why carbon dosing often promotes a cyano bloom.

Tho whole point of the article is to say:

1 - no to look for specific numbers

2 - no to the original publication by Redfield and yes to a lot of information published later

3 - yes to the benefit of comprehension and specific aplications (eg under specific conditions it is pretty easy to solve cyano problems just dosing nitrates; why it does not always work; comprehension of these ratios helps).

And I also recognize there are a lot more factors thar drive algae problems, specially biological, reproduction, competition and sometimes just plain introduction to the system.

I also wanted to provide real scientific evidence that many claims are real since we reefers like to say there is no scientific evidence of things or that scientific evidence is useless because “all systems are different”.

Why would Cyanobacteria use N2 from the atmosphere to convert it to Nh3 if it could just get NH3 from the water column? Converting N2 to NH3 requires using energy.
You are referring to Nitrates as nitrogen and that’s not correct, nitrogen comes in many forms including Nh3, No2, No3, N2 (atmospheric) and organic forms like urea and amino acids

 

[Reef and Dive]

You are making assertions, but provide no evidence to back it up. What reason do you have to make it? I do see reasons to reject it, since plenty of people have cyano under your ratios where you say it is unlikely.

In your case, where you dosed nitrate and cyano declined, do you think GFO to reduce phosphate would have had the same effect to reduce cyano?

Answer about my reef:

I’ve done many times over the years.

Some documented:

Nitrate dosing - phos nitrate “0” phosphate 0.06):


GFO saturated, cyano, changing GFO:


These are just some examples I could find from my long list of videos.

From the R2R community:

Ratio 6 - https://www.reef2reef.com/threads/can’t-get-rid-of-cyanobacteria.936208/

Nitrate 0 Phos 0.04 - https://www.reef2reef.com/threads/cyanobacteria-help.959906/

Nitrate 0 Phos 0.05 -

Cyanobacteria

Hi, Have had a tank set up running for 4 years now but a month ago have had a growth of red slime algae which I believe is called Cyanobacteria. Have tried manual removal but no luck. All tests are normal and doing regular water changes. Any ideas?

www.reef2reef.com

Nitrate 0.1 Phos 0.03 - https://www.reef2reef.com/threads/green-algae-all-over-sand.935530/#post-10585951

Just some examples I found with a quick search.

 

[sixty_reefer]

Pretty simple. Because it works. Or there is any other reason why I’ve beated cyano many times dosing nitrates that I’m not aware of.

Have you looked into heterotrophic bacteria nutrient limitation? This is bacteria that if limited by C N or P can’t assimilate nutrients

CNP comes in many different forms and affect pelagic heterotrophic bacteria and decomposing heterotrophic bacteria that cause nutrient imbalance amongst other issues

 

[Randy Holmes-Farley]

0 nitrate 0.08 phosphate = high risk of cyano (great insight on conditions and best option to dose nitrate - why would dosing nitrate “reduce” something that consumes nitrate? Great insight from understanding conditions)

Why indeed?

Regardless of whether you believe ratios are important or not, the only possible explanation is that the added nitrate boosts the growth of a competitor of some type.

Do you have a different hypothesis?

 

[Randy Holmes-Farley]

Answer about my reef:

I’ve done many times over the years.

Some documented:

Nitrate dosing - phos nitrate “0” phosphate 0.06):


GFO saturated, cyano, changing GFO:


These are just some examples I could find from my long list of videos.

From the R2R community:

Ratio 6 - https://www.reef2reef.com/threads/can’t-get-rid-of-cyanobacteria.936208/

Nitrate 0 Phos 0.04 - https://www.reef2reef.com/threads/cyanobacteria-help.959906/

Nitrate 0 Phos 0.05 -

Cyanobacteria

Hi, Have had a tank set up running for 4 years now but a month ago have had a growth of red slime algae which I believe is called Cyanobacteria. Have tried manual removal but no luck. All tests are normal and doing regular water changes. Any ideas?

www.reef2reef.com

Nitrate 0.1 Phos 0.03 - https://www.reef2reef.com/threads/green-algae-all-over-sand.935530/#post-10585951

Just some examples I found with a quick search.

Most or all of those fall outside the typical recommended ranges for nitrate. No ratio needed to see or interpret that.

 

[sixty_reefer]

I agree. Many organisms consume N and P at different ratios than one another, and there are many processes that use only nitrate or only phosphate,

Many organisms will use what will be easier to assimilate also, not just nitrates or phosphates. Nitrogen comes in many forms and so do phosphates. Keep mentioning just what we can analyse won’t take the discussion forward

 

[sixty_reefer]

Why indeed?

Regardless of whether you believe ratios are important or not, the only possible explanation is that the added nitrate boosts the growth of a competitor of some type.

Do you have a different hypothesis?

Or the energy source gets depleted, that’s a possible explanation also