Redfield Ratio - significant factor in reef tanks?

[Stigigemla]

It is hard to write in a thread like this without a reference but a few weeks ago i stumbled over a file from the Great barrier reef describing N and P in the water.
It was about 6 sampling places from north to south and the inorganic values was quite different. But the organic bound N and P was similar in all places.
The organic N was corresponding to something about 0,5 or 0,6 ppm and P was corresponding to 0,03 ppm.
I believe it might be of some significance that it corresponds to the inorganic values that are commonly accepted as target for reef aquaria.
( In Zeo driven aquaria it is possible to have lower values because N and P comes via the bacterial mulm ).
Sorry again but i do not have the reference.

I know this is highly anecdotal but if i take some water between the tumb and the index finger and rub it has a different feeling if it is aquarium water or ocean water. The ocean water feels more soapy. Dissolved organic matter? Or just holidays?

 

[Randy Holmes-Farley]

Randy, are you at all implying that NO3 and PO4 may not be necessary for coral health? I don't think you're implying that, and there must be a certain amount of NO3 and PO4 that is needed in the water column for coral (and/or their symbiotic xoozanthellae) health, or do you think (or know) that corals utilize there nutrients from a source other than the water column?

As Biom mentions, corals can thrive under conditions where nitrate and phosphate would be "undetectable" with hobby kits. This may be because:

1. They get some of the N and P from nitrate and phosphate even when present at undetectably low levels.
2. They consume solid organic foods like little organisms or organism parts.
3. They consume soluble organic matter that contains N and P ((zoox are known to use the acetate in vinegar, for example, and while not a source of N or P, it makes the point that they can uptake organics (many of which contain N or P or both) and use them).
4. They consume other inorganic sources (such as ammonia, nitrite, etc.)

Our aquaria differ from the ocean in some ways that may make some of these much harder and others more important.

Lack of food organisms in the water, for example, make make reliance on nitrate and phosphate more important.

Higher alkalinity than in the ocean may make the need higher for N and P if growth is faster than usual.

 

[Randy Holmes-Farley]

It is hard to write in a thread like this without a reference but a few weeks ago i stumbled over a file from the Great barrier reef describing N and P in the water.
It was about 6 sampling places from north to south and the inorganic values was quite different. But the organic bound N and P was similar in all places.
The organic N was corresponding to something about 0,5 or 0,6 ppm and P was corresponding to 0,03 ppm.
I believe it might be of some significance that it corresponds to the inorganic values that are commonly accepted as target for reef aquaria.
( In Zeo driven aquaria it is possible to have lower values because N and P comes via the bacterial mulm ).
Sorry again but i do not have the reference.

I know this is highly anecdotal but if i take some water between the tumb and the index finger and rub it has a different feeling if it is aquarium water or ocean water. The ocean water feels more soapy. Dissolved organic matter? Or just holidays?

Interesting.

You use this finger test a lot? Maybe we don't need Triton, just carefully calibrated fingers.

 

[Myka]

Hi Mindy, I know you expect answer from Randy, but just to give my 2 cents if you don’t mind.

Hi Stoyan. I certainly don't mind your two cents at all, and it follows my own anecdotal evidence. The only reason I asked Randy specifically is because I know who he is, and I know his qualifications to answer such questions. I also know that he is not shy to say when he doesn't know. I don't know you Stoyan, and with all respect, what are your qualifications? It sounds like you know what you're talking about, and I'd like to learn about you.

Our aquaria differ from the ocean in some ways that may make some of these much harder and others more important.

Lack of food organisms in the water, for example, make make reliance on nitrate and phosphate more important.

Higher alkalinity than in the ocean may make the need higher for N and P if growth is faster than usual.

Thank you Randy. I think this is the important part here - simulating the ocean is not always possible, and there are many ways we've been trying to make up for this in other ways. I've done NO3 and PO4 dosing many years ago as a means of experimentation, and it does seem like NO3 and PO4 dosing has become much more popular in the last few years. I don't think that's the whole answer to the equation though. Modern reef equipment and husbandry techniques have come to a point where it is surprisingly easy to create a nutrient deficient system - both in organic and inorganic nutrients. Especially in young reef tanks utilizing dry rock. My current SPS tank (using live rock) is entirely nutrient deficient and I'm experimenting with ways to make it less so by providing organic and inorganic nutrients. If I had the magic recipe I'd be wealthy.

 

[biom]

Hi Stoyan. I certainly don't mind your two cents at all, and it follows my own anecdotal evidence. The only reason I asked Randy specifically is because I know who he is, and I know his qualifications to answer such questions. I also know that he is not shy to say when he doesn't know. I don't know you Stoyan, and with all respect, what are your qualifications? It sounds like you know what you're talking about, and I'd like to learn about you. ...

Hi Mindy, I'm an ecologist, working on fish ecology and ecological modelling for almost 20 years. Thus of course doesn't qualify me as authoritative person in reef hobby, because my scientific interest are focused on fresh- and brackish water ecosystems and i'm trying to keep saltwater only as a hobby (not always that easy). Some pictures of my tank https://www.reef2reef.com/threads/bioms-reef.210887/

 

[Randy Holmes-Farley]

Nice tank, Biom. I'll post there to not derail this thread.

 

[biom]

Thank you Randy.

Modern reef equipment and husbandry techniques have come to a point where it is surprisingly easy to create a nutrient deficient system - both in organic and inorganic nutrients. ...

Very well said Mindy, i did't believe we will reach this point that fast, few years ago nitrates dosing was taboo...

 

[Habib(Salifert)]

Hey, Habib. Great to hear from you again!

Thanks Randy

It is always nice to read your posts and to interact with you.

 

[Myka]

Excellent Stoyan. Great to meet you.

Very well said Mindy, i did't believe we will reach this point that fast, few years ago nitrates dosing was taboo...

Yes, it is still taboo in most circles but the up and up. In the past I just used freshwater planted aquarium fertilizers, and just recently I've been using "pure" Sodium nitrate. In my own experiences, I've found the best coloration in SPS comes from around 1-3 ppm NO3 and "greater than 0"-0.06 ppm PO4. I've seen people claim up to 10 ppm NO3 even. On the higher end of NO3 this is not even close to the Redfield Ratio. I think the Redfield Ratio is mostly just usable to us in this definition as "N many times more than P". Achieving those nutrient levels via organic matter seems to arrive at a different "good" than arriving at those nutrient levels by dosing an almost literal shot of inorganic nitrate and phosphate. It just doesn't seem to have the same affect to me, but my jury is still out. My tank will "use up" about 1 ppm NO3 and 0.06 ppm PO4 per week, which interestingly is almost exactly 16:1. I'm not entirely sure what is happening to it. If it's merely being used by anaerobic bacteria and microalgae then it probably isn't positively affecting my SPS much.

 

[ksed]

I recently stumbled across this article in the Coral magazine July/August issue regarding a recent discovery by the University of Washington by Daniele Bianchi. The article states the following:
"Algae and photosynthetic marine animals such as corals absorb nitrogen from the surrounding water. Most nitrogen is not organically bound in living biomass but dissolved as a gas in the water, and it is not available to the vast majority of organisms. It can even outgas into the atmosphere locally , resulting in low nutrient levels. It has been assumed that this process is executed only by denitrifying bacteria that reduce the existing nitrate into nitrite and ultimately into gaseous nitrogen, which can ultimately outgas. Scientists led by Daniele Bianchi of the University of Washington have now found that zooplankton greatly influences the oceanic nitrogen cycle with its secretions. At night, zooplankton drifts toward the upper layers to consume phytoplankton there. The urine it releases makes nitrogen available to bacteria and thus promotes its conversion to gas, helping to prevent the eutrophication of certain marine areas. This discovery by Bianchi et al.shows that the population density of bacteria and the daily migration of zooplankton influence the nutrient concentration."

 

[biom]

My tank will "use up" about 1 ppm NO3 and 0.06 ppm PO4 per week, which interestingly is almost exactly 16:1. I'm not entirely sure what is happening to it. If it's merely being used by anaerobic bacteria and microalgae then it probably isn't positively affecting my SPS much.

Yes, but those quantities of N and P are only very small part of the real N and P consumption of your tank coming with fish and coral food, and you are adding them only to correct some imbalances in their consumption, so the ratio between them does not represent their consumption ratio, in contrary it represent ratio of imbalances, but since we dont know what is the N: P ratio in the food is hard to say what actual ratio of N: P consumption in the tank is. If we want to have full picture of nutrient uptake in the tank we will need to know exact amount of N and P entering tank with the food (import), and the amount of N and P exported from the tank via skimmate, detritus, N2 gas, water changes, accumulation in fish, corals and other living creatures bodies. Not a simple task unfortunately.

 

[Myka]

At night, zooplankton drifts toward the upper layers to consume phytoplankton there. The urine it releases makes nitrogen available to bacteria and thus promotes its conversion to gas, helping to prevent the eutrophication of certain marine areas. This discovery by Bianchi et al.shows that the population density of bacteria and the daily migration of zooplankton influence the nutrient concentration."

Interesting. Maybe I should start dosing copepod culture water! I wonder though, is there a difference between the excretions of fish/inverts within the system and zooplankton excretions?

If we want to have full picture of nutrient uptake in the tank we will need to know exact amount of N and P entering tank with the food (import), and the amount of N and P exported from the tank via skimmate, detritus, N2 gas, water changes, accumulation in fish, corals and other living creatures bodies. Not a simple task unfortunately.

Yes, sorry I wasn't meaning to imply that. I just thought my Redfield Ratio additions were interesting in a coincidental way. It's too complicated for us to actually get a real measurement of daily uptake, nor for us to know exactly who is uptaking/excreting what.

 

[Randy Holmes-Farley]

I recently stumbled across this article in the Coral magazine July/August issue regarding a recent discovery by the University of Washington by Daniele Bianchi. The article states the following:
"Algae and photosynthetic marine animals such as corals absorb nitrogen from the surrounding water. Most nitrogen is not organically bound in living biomass but dissolved as a gas in the water, and it is not available to the vast majority of organisms. It can even outgas into the atmosphere locally , resulting in low nutrient levels. It has been assumed that this process is executed only by denitrifying bacteria that reduce the existing nitrate into nitrite and ultimately into gaseous nitrogen, which can ultimately outgas. Scientists led by Daniele Bianchi of the University of Washington have now found that zooplankton greatly influences the oceanic nitrogen cycle with its secretions. At night, zooplankton drifts toward the upper layers to consume phytoplankton there. The urine it releases makes nitrogen available to bacteria and thus promotes its conversion to gas, helping to prevent the eutrophication of certain marine areas. This discovery by Bianchi et al.shows that the population density of bacteria and the daily migration of zooplankton influence the nutrient concentration."

Thanks for posting that. I'd not seen that Corals magazine article before, but I looked up the original scientific article, and the conclusion in it seems probably not of much impact in reef aquaria (at least to aquarist husbandry practices).

In short, what they showed was that zooplankton release ammonia that can be used by bacteria in anoxic regions to perform anaerobic ammonium oxidation (anammox), which produces N2. That may certainly be happening in reef aquaria, but we also have a lot of ammonia being produced in other ways (such as fish excretion) and so we've never really been "worried" about whether there might not be enough ammonia around for these sorts of processes.

Here's the article:
http://www.pnas.org/content/111/44/15653.short

and its stated "significance":

"Nitrogen, the limiting nutrient for primary production across much of the ocean, is converted to biologically inactive N2 by denitrification and anaerobic ammonium oxidation (anammox) in anoxic waters. Anammox requires an active source of ammonium, which can be provided by concurrent denitrification. However, anammox has been observed at high rates in the absence of denitrification, and the source of ammonium has remained cryptic. Using a combination of observations and models, we suggest that zooplankton and micronekton provide a missing source of ammonium to anoxic waters through diel vertical migrations, fueling anammox and decoupling it from denitrification. This previously overlooked mechanism can help to reconcile observations with theory and highlights the role of animals on ocean biogeochemistry."

 

[Randy Holmes-Farley]

I would add to the discussion of the Redfield ratio in relation to tank consumption rates, that even if you accounted for all of the N and P that went into the tank, there are nonbiological export methods, such as the incorporation of phosphate onto and into calcium carbonate.

 

[biom]

Thanks for posting that. I'd not seen that Corals magazine article before, but I looked up the original scientific article, and the conclusion in it seems probably not of much impact in reef aquaria (at least to aquarist husbandry practices).

Yes, i was really astonished when read this quotation from Coral magazine (I'd not read the whole article). This sentence makes me laugh. I hope Coral magazine will never quoted my articles .

"... At night, zooplankton drifts toward the upper layers to consume phytoplankton there. The urine it releases makes nitrogen available to bacteria and thus promotes its conversion to gas, helping to prevent the eutrophication of certain marine areas..."

The article of Bianchi and others is very impressive but have nothing common with the sentence above...

 

[Reef_Hobbyist]

I would add to the discussion of the Redfield ratio in relation to tank consumption rates, that even if you accounted for all of the N and P that went into the tank, there are nonbiological export methods, such as the incorporation of phosphate onto and into calcium carbonate.

Which is something we talked about in my other thread related to Pukani rock. Nice to see this all coming full circle.

And speaking of circles, we care about N and P in proper feeding of corals in a low nutrient system but also in limiting N and/or P in combating nuisance algae and cyano. Sometimes those two goals seem to be at odds with each other.

 

[Randy Holmes-Farley]

Which is something we talked about in my other thread related to Pukani rock. Nice to see this all coming full circle.

And speaking of circles, we care about N and P in proper feeding of corals in a low nutrient system but also in limiting N and/or P in combating nuisance algae and cyano. Sometimes those two goals seem to be at odds with each other.

Yes, they are. It is a problem when we try to substitute unnaturally high nitrate and phosphate for lack of normal coral foods (like small organisms) and don't want algae to do the same thing.

 

[Myka]

Yes, they are. It is a problem when we try to substitute unnaturally high nitrate and phosphate for lack of normal coral foods (like small organisms) and don't want algae to do the same thing.

Randy, are you implying that you don't advocate NO3 or PO4 dosing via chemical addition?

 

[Randy Holmes-Farley]

Randy, are you implying that you don't advocate NO3 or PO4 dosing via chemical addition?

No. I'm just saying that I agree it can be a difficult balance with respect to algae.

If it makes any given tank look better, I'm all for it.

 

[Reef_Hobbyist]

As Biom mentions, corals can thrive under conditions where nitrate and phosphate would be "undetectable" with hobby kits. This may be because:

1. They get some of the N and P from nitrate and phosphate even when present at undetectably low levels.
2. They consume solid organic foods like little organisms or organism parts.
3. They consume soluble organic matter that contains N and P ((zoox are known to use the acetate in vinegar, for example, and while not a source of N or P, it makes the point that they can uptake organics (many of which contain N or P or both) and use them).
4. They consume other inorganic sources (such as ammonia, nitrite, etc.)

Our aquaria differ from the ocean in some ways that may make some of these much harder and others more important.

Lack of food organisms in the water, for example, make make reliance on nitrate and phosphate more important.

Higher alkalinity than in the ocean may make the need higher for N and P if growth is faster than usual.

5. P can be bound up in the calcium carbonate and slowly releasing as it feeds corals and algae without being measurable in the saltwater by test kits.

Considering all these points, I am beginning to wonder if our use of the term ULNS in aquaria is a bit of a misnomer especially if we are feeding our corals. Perhaps ULNS in practice really only means low levels of inorganic N and P (as nitrate and phosphate) in the saltwater as measured by hobbyist test kits but the "System" could have medium to high nutrient levels from organic sources. Perhaps that is exactly what we see in the ocean where corals thrive in saltwater that measures low inorganic nutrient levels but high in organisms.

And if we assume corals "prefer" uptake of N and P from foods (organic sources) over inorganic sources then the inorganic N and P levels in the aquarium could be more of a factor in controlling undesirable growth of algae and bacteria than feeding corals? Or perhaps we simply cannot simulate natural coral reef levels of organic matter in an aquarium so inorganic N and P in the water do play a big factor?