Redfield Ratio Revisited – What are we doing wrong?

[sixty_reefer]

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

Ratios are a very useful tool if applied correctly, redfield ratio is used to identify limitations not to set a specific residual nitrate or phosphate. This means that anyone can use redfield to learn to identify if heterotrophic bacteria is becoming limited for example that’s why one can encounter problems with depleted phosphates.
What folks often miss is that carbon can sometimes be a limiting factor also.
Have you never herd anyone saying I got a residual phosphates and nitrates and still got Cyanobacteria, dinoflagellates etc.. if we had a home test kit for it it would be fairly easy to put the discussion forward.
the truth is that if any of the CNP nutrients get depleted it often causes a imbalance on the system. This will depend on what organisms you have in the system, limitations at the CNP level often only occur in the absence of beneficial competition

redfield ratio applied to heterotrophic bacteria can answer any question nutrient related issues in our systems and also resolve it at the nutrient level.
Look at Randy paper on carbon dosing and the ratio of nitrates to phosphates conclusion 16:1 is that coincidence? Would be interesting to see if the carbon input had been calculated also.

 

[sixty_reefer]

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.

In home aquaria we don’t have the ability to determine C , that as you know will influence N and P, we can only look at part of it.
this means that we can’t easily identify C limitations or Abundance as we can do for nitrate and phosphates. (I say nitrates and phosphates as heterotrophic bacteria can’t use ammonia or nitrite, just nitrates and organic matter depending on the type of heterotrophic bacteria)
redfield is the ratio of make up water and marine detritus in the sea in home aquaria the ratio will be different as we have different organisms creating different ratios in each aquarium although they differ from redfield we can still use it to identify limitations in home aquaria.

 

[Reef and Dive]

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

This answers:

Implications of N : P ratios in carbon dosing

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

Yes sure. Cyano is treated in nature with lanthanum.

But sometimes phosphate is just too low and nitrate dosing changes things.

Why would Cyanobacteria use N2 from the atmosphere to convert it to Nh3 if it could just get NH3 from the water column?

Every competitor usually does that. So the limitting factor comes when all these options are low. Usually ammonia is also depleted fast in our reefs, reason why it is normally not detected.

Keep mentioning just what we can analyse won’t take the discussion forward

IMHO we can obtain very solid information with what we measure, we don’t need to dismiss all of that based on possible aliens around.

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.

It’s entirely about that!!!
It is all about competition. Cyano is outcompeted by other with high nitrates, but thrives easy when there is a lot of phosphate but not enough nitrates. Simply because they are diazotrophic and others are not.

Dinos, for example, love nutrients, but thrive when they are low, when other competitors are scarce.

 

[Sisterlimonpot]

50 nitrate, 0.5 phosphate = low risk of cyano

What I'm having a hard time understanding is if this example ratio is considered low risk for cyano, then if we lowered the numbers but kept the ratio the same: 1 nitrate, 0.01 phosphate, then the chance for cyano outbreak would still be a low risk.

Are you suggesting that 1 nitrate and 0.01 phosphate will still be a low risk for cyano?

Focusing on the ratio doesn't make much sense. And the point Randy makes seems to hold up better to what I've experienced.

In order to keep the risk of cyano low, it's nothing to do with any relationship between N and P, rather not allowing the numbers to go below a particular threshold.

From experience in the case of cyano it seems that the underlying factor is low nitrates, regardless of its relationship to phosphates.

 

[sixty_reefer]

Every competitor usually does that. So the limitting factor comes when all these options are low. Usually ammonia is also depleted fast in our reefs, reason why it is normally not detected.

ammonia is depleted faster in mature systems over younger systems due to mature systems have developed more natural methods of competition, every organism that cover the rock surface is photosynthetic, large coral colonies are also photosynthetic etc.. they all thrive in ammonia.
This should answer the question on why mature system often don’t have as much nuisance problems Vs younger systems that have hare rocks in the low nitrates and phosphates question. which is true, how often we see dinoflagellates taking over mature reefs in this conditions Vs new tanks.
ammonia is always present it just at very low levels and usually we need to use spectrometry to interpret the residual.
In addition not all ammonia is converted to nitrates due to being used by several photosynthetic organisms before nitrifying bacteria can oxidised it to nitrates

It’s entirely about that!!!
It is all about competition. Cyano is outcompeted by other with high nitrates, but thrives easy when there is a lot of phosphate but not enough nitrates. Simply because they are diazotrophic and others are not.

Dinos, for example, love nutrients, but thrive when they are low, when other competitors are scarce.

this is we’re I don’t agree during low nitrates or low phosphates we often overlook the role of heterotrophic bacteria. There is two important roles for heterotrophic bacteria one is to oxidise nitrates and some phosphates by the pelagic bacteria and the other role is to reduce organic matter like uneaten food and fish waste (source of constant ammonia) by bacteria like pseudoalteromonadaceae and bacillaceae this heterotrophic organisms are responsible for decomposition of organic matter and if limited in growth by NCP they can’t function allowing for ammonia to rise due to the uneaten food ins organic matter not being assimilate from the water column.

we need to take into consideration that the redfield ratio is very similar if not identical to the nutritional needs of heterotrophic bacteria that in most systems are the sole responsible organisms for balance in aquaria

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[Lasse]

This will be a long post but I think its important to shows where my thoughts is coming from.

There is too many cases where it had been shown that rising the NO3 concentration up to around 2 - 3 mg/L combat cyanobacteria mats of different species helps in more than 80-90 % of the cases. Of cause - there is no scientific studies that I´m aware of that can show that it works or the mechanism behind but for me - it is in my husbandry because I want to base my husbandry on science and proven experience

The science in this case is not from the aquarium field - nor from saltwater but based on studies of eutrophicated freshwater lakes in Scandinavia. During summer its often forms an anaerobic environment above or in the upper layers of the sediment in these lakes. Some of these lakes get cyanobacteria blooms - some not- The phosphate was very low - if not zero but the NO3 concentration was from zero to over 2 mg/L. It looks like it was a threshold over 2 ppm mg/L NO3 - below that threshold cyanobacteria bloom - over - no cyanobacteria bloom. It important to stress that it was not cyanobacteria mats in these cases - it was phytoplankton forms of cyanobacteria that migrate vertically. Phosphorus was depleted in the open water column but this jerks migrate vertically down to the anaerobic layers during night time, collect phosphorous and migrate up in the sunlight during day. They found another phosphorous source thatn was blocked for other phytoplankton. They also was able to form their own N with help of their ability to convert N2 gas into NH4. Conclusion was that when both PO4 and NO3 was absent or at very low values - the migrating cyanobacteria went down to the anaerobic layer as said before. However - in lakes with 2 ppm NO3 in the water column - it seems like there was no extra phosphorous to be picked up in the anaerobic part and it did not favour the migrating cyanobacteria phytoplankton. Unfortunately, the report is only available in Swedish but here is the English summary

This study has focused on why, and when, cyanobacteria (blue-green algae) mass develop in fresh water. Eight different lakes were studied regarding phytoplankton composition and physical and chemical factors. The phytoplankton were divided into several groups based on their ability to perfom vertical migrations and their potential to develop heterocytes (nitrogen-fixing cells). The results were analysed with stepwise regression and principal component analysis (PCA). Total nitrogen, measured at the bottom was the chemical variable that strongest correlated (positively) with the biomass of non-migrating algae. The chemical variables that correlated strongest to vertical migrating cyanobacteria without heterocytes was total phosphorus at the bottom (positive correlation) and nitrate at the surface (negative correlation). A similar, but weaker, relationship was observed between heterocystous cyanobacteria, nitrate and total phosphorus. Nitrogen at the bottom was the most important chemical variable that separated the migrating algae from the non-migrating algae. A positive relationship occurred between nonmigrating algae and nitrogen at the bottom whereas the relationship was inverse regarding the migrating phytoplankton. Our interpretation of the results regarding why vertical migrating phytoplankton proliferate at low nitrogen levels is partly that nitrogen deficit is compensated by cyanobacterial nitrogen fixation and partly that nitrogen deficit at the bottom permits release of phosphate from the sediment. Low levels of nitrate in the sediment may cause deficit of electron acceptors at bacterial decomposition of organic material. Instead of nitrate, sulphate can be used as an electron acceptor which results in the formation of hydrogen sulfide. The presence of hydrogen sulfide, in turn, causes the release of phosphate from the sediment. Results from the retrospective study in Lake Finjasjön, Sweden, showed a strong correlation between internal phosphorus release and the biomass of vertical migrating algae and total algal biomass respectively. A negative relationship was found between internal phosphorus release and non-vertical migrating algae. There existed no relationship between the biomass of any algal group and the net release of nitrogen whatsover. An increase in nitrogen in the lake did, consequently, not effect the algal biomass in the same way as phosphorus. These results confirm earlier discoveries by Schindler and Hellström which showed that the algal biomass was governed by the phosphorus concentration whereas the nitrogen deficit is compensated by nitrogen fixation.

I recommend to run chapter 5 through Google translator - there is a lot of goodies in that chapter also according to
jelly-producing cyanobacteria without heterocytes (the mats forming cyanobacteria belongs to this group)

However - back around 2008 (when zero NO3 was the holy graal and cyanobacteria mats was everywhere) this discussion of adding NO3 based on this report was started among Swedish saltwater aquarists - let me say that the persons advocate this could be (in the beginning) counted on the left hands thumb. However some aquarists with freshwater experiences chime in and argue that it works against mats in freshwater aquarium. With time - this method (to keep up NO3 concentrations to around 2 mg/L has been the rule based on both competition of N and release of P from the gravel/stones. The thought is that the jelly formed by photosynthesis during day create a anaerobic environment below the mat, anaerobic heterotopic bacteria use sulfate in their metabolism in absence of both oxygen and NO3 - create hydrogen sulphide as a metabolit and in it turn make inorganic PO4 be released from its metal bounded forms) The jelly itself is energy (mostly polysaccharides) and could be used for proliferation during night. Therefore - to stirr or suck up the mats in the evening (when they ar largest) will be a second task to do.

Its true that there can be cyanobacteria mats even in higher NO3 concentrations but IME - its more seldom - maybe 20% of the cases

I´m not saying that the discussion above is the absolute true but it lead to a husbandry that works in most cases.

And its here I can see that the ratio N/P in the water column is important. If you get to high ratio the photosynthesis in the zooxanthella can give a P defiency and a bleaching event, IMO it is important to stress that in our case - the cyanobacteria has one environment (the substrate) and the corals live in another habitat - the free water - as long as the mats not cover them. With other words and IMO - if you want to have - as I - around 2-5 mg/L NO3 - you can´t run below 0.06 mg/L in PO4

Sincerely Lasse

 

[Lasse]

heterotrophic bacteria one is to oxidise nitrates

I hope its a typo - denitrification is a reducing process (take away O)

Sincerely Lasse

 

[sixty_reefer]

I hope its a typo - denitrification is a reducing process (take away O)

Sincerely Lasse

I meant to say assimilate, it’s only morning here

 

[Lasse]

it’s only morning here

Yes I´m 1 hour before you - 2 first cup of coffee already consumed

Sincerely Lasse

 

[sixty_reefer]

Yes I´m 1 hour before you - 2 first cup of coffee already consumed

Sincerely Lasse

This discussion require a lot of it at this time of the day

 

[Randy Holmes-Farley]

There is too many cases where it had been shown that rising the NO3 concentration up to around 2 - 3 mg/L combat cyanobacteria mats of different species helps in more than 80-90 % of the cases. Of cause - there is no scientific studies that I´m aware of that can show that it works or the mechanism behind but for me - it is in my husbandry because I want to base my husbandry on science and proven experience

I do not doubt that, and it makes perfect sense that an organism that may be able to fix its own nitrogen from N2 in the air would thrive more than other organisms at low available N (such as nitrate or ammonia).

As to the utility of ratios in this scenario...

If the recommendation for a reef tank is 2-10 ppm nitrate and 0.03 to 0.1 ppm phosphate, one would never be in that situation, or if one were, one would be boosting nitrate anyway, without resorting to computing ratios and trying to decide where the cyano "risk level" fell.

 

[Reef and Dive]

I do not doubt that, and it makes perfect sense that an organism that may be able to fix its own nitrogen from N2 in the air would thrive more than other organisms at low available N (such as nitrate or ammonia).

As to the utility of ratios in this scenario...

If the recommendation for a reef tank is 2-10 ppm nitrate and 0.03 to 0.1 ppm phosphate, one would never be in that situation, or if one were, one would be boosting nitrate anyway, without resorting to computing ratios and trying to decide where the cyano "risk level" fell.

My point in understanding ratios is more about comprehension of the relations of organisms under different environments, and less about suggesting target ranges for reef keeping. I’m more into knowing why I’m doing something than going after a number.

Sometimes it happens the opposite: I know my phosphate. Some cyano appears. I use it as an indicator of my nitrates and I just know pretty soon it lowered. As it can be seen on my display over time it has been managed pretty easy with that extra info.

 

[Reef and Dive]

Just to keep it clear, the 1.53 multiplication of conversion nitrate [ppm] : phosphate [ppm] to nitrogen : phosphorus comes from this:

Molar weight NO3: [NO3 ppm]/62

Molar weight PO4: [PO4 ppm]/95

Redfield Ratio: ([NO3 ppm]/62)/([PO4 ppm]/95) or 1.53* [NO3 ppm]/[PO4 ppm]

 

[Eric R.]

Just thought I'd drop this video clip here, in case folks don't watch/listen to reefbum.

 

[Reef and Dive]

Just thought I'd drop this video clip here, in case folks don't watch/listen to reefbum.

I left my comment on the video.

But I honestly believe most people that dismiss the importance of stoichiometric (NOT REDFIELD) ratios simply chose to ignore many of the articles I provided on the first page and even to read the entire text.

This was not intended to be a “my opinion” topic, but came after a pretty long research of scientific evidence.

But no problems, no intention of being a rule creator here, just knowledge that I use to reef keeping.