Light, Alkalinity, Nutrients.

[Nano sapiens]

Veerrrryyy interesting! May I ask about your set up Ralph? No ? A lot of different corals?

Thanks for the interest. Yes, correct, no mechanical or chemical filtration. Just a return pump, heater, lights, thermometer and a gravity-fed ATO. I've run a few different medium sized tanks in the same way for 30+ years...now just keeping it simple and easy with this little mixed reef nano I started back in 2008:

https://www.reef2reef.com/threads/nano-sapiens-12g-ye-olde-mixed-reef.90171/

Ralph.

 

[mcarroll]

Here's an older one of mine about phosphorus in a *lightly* loaded tank - imagine if it was heavily fed! Total P was about 0.5 mg/L and is slowly converted to soluble, reactive orht0phosphate.

Is a link or pic missing from that post?

 

[mcarroll]

Any claim that high ALK has no affect on burnt tips is simply false unless you can somehow validate many other conditions like nutrients, flow, lighting, etc.

+1

But isn't it equally true that a claim that alk has any effect at all is also false unless you control/validate the other conditions? (Yes.)

This is the idea I was beating up and explaining poorly in earlier posts!

Please allow me to beat on it a little more.

The reality:

Some user of "carbon-dosing+GFO" with burnt tips blamed alk once, and for some reason (not saying no reason) it just stuck. ​

​

Burnt tips was instantly a "high alk problem".​

​

And just as instantly "high alk was bad for SPS".​

In the flawed reality of that analysis:

• Nutrient levels, carbon dosing and GFO-use all get a "bye".
• I suppose because "ULNS is flawless" therefore these factors are also blameless.

But when we're sorting evidence on alk, nutrients and carbon dosing, to me it looks like this:

1. Many folks have run high alk (dKH ≥8-11+) SPS systems before – it was considered desirable and "worked" without issues.
   Obviously, high alk is not the problem per se, even if it's related in the current story somehow.
2. Very few folks in the hobby's history have ever run zero nutrient aquariums before. It makes sense that we would find some side-effects.
3. Very few folks in the hobby's histroy have ever run elevated carbon aquariums before. It makes sense that we would find some side-effects.

#2 and #3 deserve all the scrutiny because Elevated C and zero P (or N):

• are unprecedented in terms of being ubiquitous conditions in the home reef
• have predictable negative outcomes in the wild

Taking a trip back to 2004 may give us all the right perspective....a few Reefkeeping.com articles:

• Reef Aquarium Water Parameters
  By our own Dr Holmes-Farley. This is for any who doubt that high alk ever was a solid recommendation for stony corals. (420, 11, 1350 y'all! )

...and....

• The Old Becomes New, Yet Again: Sandbeds and Vodka
• The Old Becomes New, Yet Again: Sandbeds and Vodka - Part II
  Both by Eric Borneman.....read this for an old perspective on Carbon dosing that I still hold today. Wish I'd stumbled upon this article sooner – maybe some others will too! (I miss this guy!!!)

The nutshell summary is that initial indications back in the mid-1990's were that carbon dosing could be problematic.

So carbon dosing was never the harmless miracle that folks treat it as today. Instead, it's a double edge sword like any technology. We should not be surprised.

Regardless, carbon-dosing+GFO has become popular as the key to letting anyone keep as much livestock as they want while having no algae grow.

Here's another breakdown of my thoughts:

• High HCO3
  • If there's a role for high alkalinity, I'd like to see a stronger, less-hypothetical case made as to how and why. Too many reefs aquariums have historically used very high alkalinity levels without issue. Also, why didn't burnt tips show up on those tanks? And further, why wasn't "high alk" driving people's nutrient levels through the floor if it was really driving growth like we thought it was????
  • I suspect that any reason found will ultimately lead or point to a nutrient issue – N, P or C, or maybe a combination. Alk is not the issue, IMO.
  • I remember folks would claim back in the day that raising Ca or alk above normal would increase growth, but I remember the effects being inconsistent across all tanks and that the effects seemed to diminish the higher the levels went.
  • I do not remember any deleterious effects though – merely cases that lacked super-fast growth when the numbers were considered.
  • I'm not convinced that elevated alk is such a strong driver of growth on it's own – this would depend on the overall environment, right?
  • I do think it can be a strong limiter though and it naturally exists at a low concentration compared to other minerals, so increasing concentrations might be alleviating a limit more than driving growth.
• High P
  • I still have not seen anything during my own research that indicates that "high alk" or "high phosphates" are actually harmful to corals. The opposite for P, in fact:
    • Available phosphorous has been shown to literally give protective effects to corals and to be associated with healing as well as serving other crucial biological needs.
    • Unavailable phosphorus is associated with numerous problems including death.
• High C
  • I've shown the research I found which affirms the negative effects of elevated carbon on the coral ecosystem, specifically on the microbial loop.
    • Corals host many endosymbionts, from bacteria, to cyano, to dino's, etc that are all integral with this microbial loop.
    • So to me it's really only a question of what effects elevated carbon levels have on corals, not whether corals would be affected.
    • And there's nothing I've read so far that would indicate anything other than negative side-effects are likely.

Still looking for more research though!!!! Share if you know of any!!!

Here's another one I found that might clear it mostly up:
Role of elevated organic carbon levels and microbial activity in coral mortality

Very telling.

 

[CodyRVA]

+1

But isn't it equally true that a claim that alk has any effect at all is also false unless you control/validate the other conditions? (Yes.)

This is the idea I was beating up and explaining poorly in earlier posts!

Please allow me to beat on it a little more.

The reality:

Some user of "carbon-dosing+GFO" with burnt tips blamed alk once, and for some reason (not saying no reason) it just stuck.

Burnt tips was instantly a "high alk problem".

And just as instantly "high alk was bad for SPS".​

In the flawed reality of that analysis:

• Nutrient levels, carbon dosing and GFO-use all get a "bye".
• I suppose because "ULNS is flawless" therefore these factors are also blameless.

But when we're sorting evidence on alk, nutrients and carbon dosing, to me it looks like this:

1. Many folks have run high alk (dKH ≥8-11+) SPS systems before – it was considered desirable and "worked" without issues.
   Obviously, high alk is not the problem per se, even if it's related in the current story somehow.
2. Very few folks in the hobby's history have ever run zero nutrient aquariums before. It makes sense that we would find some side-effects.
3. Very few folks in the hobby's histroy have ever run elevated carbon aquariums before. It makes sense that we would find some side-effects.

#2 and #3 deserve all the scrutiny because Elevated C and zero P (or N):

• are unprecedented in terms of being ubiquitous conditions in the home reef
• have predictable negative outcomes in the wild

Taking a trip back to 2004 may give us all the right perspective....a few Reefkeeping.com articles:

• Reef Aquarium Water Parameters
  By our own Dr Holmes-Farley. This is for any who doubt that high alk ever was a solid recommendation for stony corals. (420, 11, 1350 y'all! )

...and....

• The Old Becomes New, Yet Again: Sandbeds and Vodka
• The Old Becomes New, Yet Again: Sandbeds and Vodka - Part II
  Both by Eric Borneman.....read this for an old perspective on Carbon dosing that I still hold today. Wish I'd stumbled upon this article sooner – maybe some others will too! (I miss this guy!!!)

The nutshell summary is that initial indications back in the mid-1990's were that carbon dosing could be problematic.

So carbon dosing was never the harmless miracle that folks treat it as today. Instead, it's a double edge sword like any technology. We should not be surprised.

Regardless, carbon-dosing+GFO has become popular as the key to letting anyone keep as much livestock as they want while having no algae grow.

Here's another breakdown of my thoughts:

• High HCO3
  • If there's a role for high alkalinity, I'd like to see a stronger, less-hypothetical case made as to how and why. Too many reefs aquariums have historically used very high alkalinity levels without issue. Also, why didn't burnt tips show up on those tanks? And further, why wasn't "high alk" driving people's nutrient levels through the floor if it was really driving growth like we thought it was????
  • I suspect that any reason found will ultimately lead or point to a nutrient issue – N, P or C, or maybe a combination. Alk is not the issue, IMO.
  • I remember folks would claim back in the day that raising Ca or alk above normal would increase growth, but I remember the effects being inconsistent across all tanks and that the effects seemed to diminish the higher the levels went.
  • I do not remember any deleterious effects though – merely cases that lacked super-fast growth when the numbers were considered.
  • I'm not convinced that elevated alk is such a strong driver of growth on it's own – this would depend on the overall environment, right?
  • I do think it can be a strong limiter though and it naturally exists at a low concentration compared to other minerals, so increasing concentrations might be alleviating a limit more than driving growth.
• High P
  • I still have not seen anything during my own research that indicates that "high alk" or "high phosphates" are actually harmful to corals. The opposite for P, in fact:
    • Available phosphorous has been shown to literally give protective effects to corals and to be associated with healing as well as serving other crucial biological needs.
    • Unavailable phosphorus is associated with numerous problems including death.
• High C
  • I've shown the research I found which affirms the negative effects of elevated carbon on the coral ecosystem, specifically on the microbial loop.
    • Corals host many endosymbionts, from bacteria, to cyano, to dino's, etc that are all integral with this microbial loop.
    • So to me it's really only a question of what effects elevated carbon levels have on corals, not whether corals would be affected.
    • And there's nothing I've read so far that would indicate anything other than negative side-effects are likely.

Still looking for more research though!!!! Share if you know of any!!!

Here's another one I found that might clear it mostly up:
Role of elevated organic carbon levels and microbial activity in coral mortality

Very telling.

Great info!

At this point, my general thesis is... A variety of conditions in which coral can survive and even thrive exists; none of which is solely achieved or defined by one aspect or component. While this implies resiliency, the slightest imbalance or misconfiguration of these components will result in coral loss on some scale; which is directly relative to the composition of the given coral.

Seems clear that keeping coral, all types, at varying ranges (dKH) of ALK is quite possible and can be done successfully. Making the claim that you can't have high ALK or low ALK is inaccurate and over simplified. There's much more tied to ALK than simply ALK... or CA, MG, PO4, NO3...

IME in recently dealing with my SPS die out, I've absolutely bought into the fact that what happened was due to a combination of issues. Component A got messed up, because Component B fluctuated, and because of a fluctuating component B, then component C went haywire as well. It's very possible and likely there is a root cause, but to manage and resolve the problem we need to understand not only how that one root issue occurred, but also the affect it had on these other components and how it caused a plethora of other issues as well as how we correct all these things. This doesn't really answer any questions nor is it an over encompassing resolution to this thread, but... there are a lot of pieces to the pie, far more than simply monitoring "the big 3." I can at least say that I've acquired a much greater appreciation for this now than I did before.

 

[mcarroll]

Great summary analysis!

I can at least say that I've acquired a much greater appreciation for this now than I did before.

Amen to that!

I think I feel the same almost every day. This stuff is amazing.

 

[Dana Riddle]

@mcarroll - Thanks for the references. One linked paper discusses photosynthetic yield and electron transport rate (efficiency and rate of photosynthesis) as linked to nutrient levels. According to that paper, and yield below 0.5 indicates a stressed coral. If this is indeed the case, corals in Hawaii demonstrate a yield of 0.3 under conditions of low light (similar to that used in the referenced experiment) and would be classified as 'sick' (my term, not theirs'.) So, it appears that nutrient ratios (especially N) would be used as an indicator of coral health.
My alkalinity experiments were conducted in water where alkalinity had been naturally destroyed by the nitrification process, hence nitrate was high. Back to the old drawing board...

 

[Lasse]

Forgot to answer this part...

@Lasse I think you were talking about something like this? Heat + Nutrients? (Someone! LOL).

I wish it was me - but not - I was probably talking about heat and acidification of the seas

But for now I´m sure that i the next 10 pages of this thread will solve the problem with bleaching of acropora in an aquarium. Why?


Because some of the brightest Super Nova’s of reef chemistry is discussing in the same thread!!!!!

Dana Riddle and Randy Holmes Fairly is well-known for all at reef2reef and Hans-Werner is well-known for us Europeans (and if you know his surname – you will realize that he is most mentioned persons of all in here )

And there is more persons with knowledge in the thread

Some remarks from a black hole in this discussion

According to phosphorus and nitrogen cycle in an aquarium. For fresh water plants – this is a known problem with its own solutions.

One of the first methods that was developed in order to solve this problem is a system named PMDD (Poor Mans Dupla Drops from the beginning - nowadays they prefer Poor Mans Dosage Drops ) Aquarium Fertilizer.

This two compounds (N and P) is the most important nutrients for freshwater plants (together with inorganic carbon – CO2). This three plus potassium and some micro nutrients is administrated in surplus in order to grow freshwater plants. They normally use KNO3 (Potassium and Nitrogen source), KH2PO4 (Potassium and Phosphorus source). CO2 addition (down to pH 6.7 -7.0) (inorganic carbon source) and some micronutrients (trace elements)

KNO3 is chosen because it has shown up that adding a nitrogen source containing ammonium (NH4) will give the freshwater algae a growth boost.

Of many reasons – this is not a good way to farm corals in saltwater

But there has been a new fresh water plant method (or let us say an old school method) developed that depend on nutrient sinks – its named the Walstad method after Diana Walstad book The Ecology of the Planted Aquarium.

And here I think we have the Gordian knot

The methods we use today in order to lower the nutrient levels according the ULN theory will empty all of our nutrient sinks. BB, cleaning, micro bubbling, heavy skimming, GFO, adding organic carbon in order to promote bacterial growth that either will be eaten or skimming out, curing LS, denitrification filter and so one. We a rinsing out every thinkable P and N atom in the whole system.

All of this taking together make it sooner or later necessary to ad this nutrients in the “pills” form to our tank – because the zooxanthellae need inorganic compounds – they are plants.

With nutrients sinks we can more easily control the release of nutrients and the system can be self-regulating. The return of the DSB in one or another form @Paul B you have understand this a long time ago

About the bleaching of some corals and high alkalinity (read HCO3) – can it have the same reason as seen in freshwater plants in heavy light and access to high amounts of CO2 – too much photosynthesis and problem to get rid of surplus oxygen and therefor a formation of oxygen radicals. We knows that some species can use HCO3 as a source of CO2.

During the last 5 years many thing has happen – LEDs give us the possibility to concentrate the power there it is give the most effect of photosynthesis, streamers has given us possibilities to take away surplus oxygen from the microcosms around our corals, effective skimmers has given us the possibility to degas the water (from ammonia gas - NH3, from surplus oxygen and to balance the CO2 content of the water) nutrient export and other things. It is not surprising that we get problems because we do not understand the wonderful Swedish word “Lagom” I do not translate it but see here



Sincerely Lasse

 

[Lasse]

+1


High C

• • I've shown the research I found which affirms the negative effects of elevated carbon on the coral ecosystem, specifically on the microbial loop.
    • Corals host many endosymbionts, from bacteria, to cyano, to dino's, etc that are all integral with this microbial loop.
    • So to me it's really only a question of what effects elevated carbon levels have on corals, not whether corals would be affected.
    • And there's nothing I've read so far that would indicate anything other than negative side-effects are likely.

Still looking for more research though!!!! Share if you know of any!!!

I do not have any scientific links according to add an organic carbon source and health of corals. Only some remarks – I think Borneman was wrong than he stated that there was no evidence that the heterotroph bacteria population was growth limited because of lack for fast organic carbon. As the last article you refer to state – I´m convinced that the heterotroph bacteria population in our aquariums is for the most events growth limited by lack of fast organic carbons.

In the denitrification case – there is a tons of articles that state that fast organic carbons sources is essential for good denitrification. However - In this case – the fast organic source is used together with nitrate in the citric acid cycle – not primary for growth.

And denitrification demand 0 in oxygen – the cases he referred to (in the upper layer of sediments) probably was another process little known at that time (article from 2004 - the process I´m thinking of was discovered 1999) – the Anammox process – one of the most important processes in marine sediments. If this happens in our aquaria is unknown but the process take a long, long time to mature - in one or two years I´ll try to convinst people reserching this process to look at my DSB

In the case of the article about mortality of corals caused by adding sugar – they use rather high concentration of sugar (up to 25 ppm) – it correspond to 2,5 gram sugar/100 liter – around 5 gram (or 5 ml 50 % vodka/100 l) If you add that – you got in trouble for sure.



Sincerely Lasse

 

[Nano sapiens]

And denitrification demand 0 in oxygen – the cases he referred to (in the upper layer of sediments) probably was another process little known at that time (article from 2004 - the process I´m thinking of was discovered 1999) – the Anammox process – one of the most important processes in marine sediments.

Sincerely Lasse

The original observation that both nitrification and dissimilatory denitrification can occur in the upper sand bed layer is essentially correct. Mostly anaerobic denitrifying bacteria species exist within the sand grain micro pores, while the aerobic nitrifying bacteria exist on the more exposed surfaces. The term scientists use when both nitrifers and denitrifiers are in close proximity is 'Coupled' ('The Reef Aquarium', Vol 3/Sprung/Delbeek, reference talen from Webb and Wiebe, 1975; Webb et al., 1075; D'Elia, 1988). Since many reef aquariums with a shallow sand bed have very low/undetectable nitrate levels without the aquarist doing anything special to mitigate nitrate, this provides at least a partial explanation.

Ralph.

 

[Lasse]

The original observation that both nitrification and dissimilatory denitrification can occur in the upper sand bed layer is essentially correct. Mostly anaerobic denitrifying bacteria species exist within the sand grain micro pores, while the aerobic nitrifying bacteria exist on the more exposed surfaces. The term scientists use when both nitrifers and denitrifiers are in close proximity is 'Coupled' ('The Reef Aquarium', Vol 3/Sprung/Delbeek, reference talen from Webb and Wiebe, 1975; Webb et al., 1075; D'Elia, 1988). Since many reef aquariums with a shallow sand bed have very low/undetectable nitrate levels without the aquarist doing anything special to mitigate nitrate, this provides at least a partial explanation.

Ralph.

I´ll think you are wrong - denitrification is one process that by definition demand 0 oxygen. The environment must be anoxic. Denitrification means that facultative anaerobic bacteria will use nitrate instead of oxygen as electron acceptor in the citric acid cycle. The process need a fast organic carbon source like methanol, ethanol, simple sugars or vinegar in order to serve as an electron donor. E.g. – the process need both nitrate (nitrite, nitrite oxide or nitrous oxide can also be used) and a fast organic carbon source. This carbon source can be added or produced in an anaerobic breakdown process from other organic compounds (one such process is hydrolysing).

Final product N2 gas.

If a real denitrification should take place in a swallow sand bed as you describe, its need rather stable anoxic conditions in the pores and adding of a fast organic carbon source. In a DSB the whole process including hydrolysing can take place but it needs time

The process you are referring to as dissimilatory denitrification it´s normally named DNRA (dissimilatory nitrate reduction to ammonium) and the final result is ammonia (NH4)

The Anammox process was unknown when your references was written but its probably rather important I normal sediments. Its use nitrite in order to convert ammonia to nitrogen gas.


In natural sediments all of these three pathways occur. A model of the nitrogen cycle can be seen in this link.

https://en.wikipedia.org/wiki/Anammox#/media/File:The_nitrogen_cycle_Arrigo.png

But for now I think we have to go back to track of the thread - light-alkalinity-nutrients

Sincerely Lasse

 

[Nano sapiens]

I´ll think you are wrong - denitrification is one process that by definition demand 0 oxygen. The environment must be anoxic. Denitrification means that facultative aerobic bacteria will use nitrate instead of oxygen as electron acceptor in the citric acid cycle. The process need a fast organic carbon source like methanol, ethanol, simple sugars or vinegar in order to serve as an electron donor. E.g. – the process need both nitrate (nitrite, nitrite oxide or nitrous oxide can also be used) and a fast organic carbon source. This carbon source can be added or produced in an anaerobic breakdown process from other organic compounds (one such process is hydrolysing).

Final product N2 gas.

If a real denitrification should take place in a swallow sand bed as you describe, its need rather stable anoxic conditions in the pores and adding of a fast organic carbon source. In a DSB the whole process including hydrolysing can take place but it needs time

The process you are referring to as dissimilatory denitrification it´s normally named DNRA (dissimilatory nitrate reduction to ammonium) and the final result is ammonia (NH4)

The Anammox process was unknown when your references was written but its probably rather important I normal sediments. Its use nitrite in order to convert ammonia to nitrogen gas.


In natural sediments all of these three pathways occur. A model of the nitrogen cycle can be seen in this link.

https://en.wikipedia.org/wiki/Anammox#/media/File:The_nitrogen_cycle_Arrigo.png

But for now I think we have to go back to track of the thread - light-alkalinity-nutrients

Sincerely Lasse

I am a bit surprised by your dismissal of the importance of anaerobic micro pore sites inside of sand grains to the reef aquarium denitrification process, but to each their own.

Yes, agreed, back to the topic at hand...

 

[mcarroll]

In the case of the article about mortality of corals caused by adding sugar – they use rather high concentration of sugar (up to 25 ppm) – it correspond to 2,5 gram sugar/100 liter – around 5 gram (or 5 ml 50 % vodka/100 l) If you add that – you got in trouble for sure.

This along with the generally harmful effects known from elevated carbon levels seems to be two chapters of the same story to me.

The story is compelling me to believe that while elevated carbon levels may be good for causing bacterial blooms, elevated carbon levels are not healthy for the critters we want to encourage (corals) or their microbial allies.

Direct harm to corals from elevated carbon levels is possible (per that link). I think some folks may have been in denial of the possibility.

But direct harm is not the only kind of harm that happens or the only kind that matters. (See the earlier link about carbon and brown tides.)

I admit I don't know how to get back on topic from here.....what are we talking about again!?

 

[mcarroll]

the ULN theory will empty all of our nutrient sinks.

+1

You're the first other person I've seen observe on this.....I think I referred to them as microbial loops or nutrient loops vs sinks but I had the same essence in mind.

 

[Lasse]

Some points to discuss further. Not in order of importance

High alk, High lighting -> High photosynthesis from the Zooxanthella (with help of the coral animals (or the clade of zooxanthellas) in converting HCO3 to CO2)

High photosynthesis – high demand of nutrients for the zooxanthella

Low or no nutrients in the water -> Zooxanthella and the coral animal concur about the nutrients in the plasma (bloodstream?)

No extern feeding of the coral animal – the coral animal is depending of nutrients in the water and/or produced by the zooxanthellae.

Different processes in different part of the coral according to calcification

Stress

The regulation system go nuts

Are we sure that the bleaching of the corals depend on zooxanthella leaving the coral? Can’t they instead been eaten up by the coral animal instead – in a desperate attempt to survive?

The animals last energy reserves has gone

Pathogen bacteria and other organism defeat the coral animal for the substrate to sit on – no energy for fighting back

Corals with thin layers of animals (and zooxanthella) more vulnerable than the opposite

Corals depended of trapping small animals, bacteriaplankton and phytoplankton with help of polyps more vulnerable than corals mainly depending of bacteria production in the mucus

High photosynthesis – high production of oxygen – high risk of forming active oxygen radicals

Low or no energy reserves – can´t fight the oxidants with antioxidants

Please - fill in with more

Sincerely Lasse

 

[Dana Riddle]

This is getting way off topic, but Lasse mentioned bleaching and ultimate fate of zooxanthellae... I'm going to start a new thread.

 

[taricha]

"Most recently, however, we could demonstrate that corals exposed to elevated nitrogen levels were more susceptible to bleaching when exposed to heat and light stress [28•]. Interestingly, the detrimental effects observed in these experiments could be attributed to the relative undersupply of phosphorus that resulted from the enhanced demand of the proliferating zooxanthellae population rather than to the elevated nitrogen levels themselves (Figure 1 ; Figure 2)".
---

I read this whole thread just to make sure someone had posted this paper. Check the linked figures. It's an eye opener, and practical. (I took its advice and reversed a bleaching in my tank by adding P recently.)
3 other related comments:
Talking about level of X resource (alk) being too high can often be reframed as Y resource being too low - sometimes the complimentary view is more helpful.
P & N are not symmetric, low of one and high of other is not interchangeable with the reverse.
The coral and its symbiodinium are different animals with different limitations. Bleaching can be a situation where one part of pair does fine, but the other is stressed.
Oh, and very desirable coral colors are found at the verge of coral death.

 

[Flippers4pups]

"Oh, and very desirable coral colors are found at the verge of coral death. "

So as we know, ULNS and very high nutrient systems are at the extreme ends of the potential "death zones".

One is intended (ULNS) and the other is lack of husbandry.

Middle ground is optimal.

 

[mcarroll]

My only defense for how off-topic this thread has gotten is how much folks obviously need this conversation to happen.

Given how far along the conversation has gotten though, I would almost request that we just go with the flow and simply update the title and first post to more accurately reflect the thread. Then just create a new thread to re-ask the original question.

Maybe this post could then be moved to the Aquarium Nutrition forum when it can live out it's life in a more "on-topic" fashion?

So as we know, ULNS and very high nutrient systems are at the extreme ends of the potential "death zones".

One is intended (ULNS) and the other is lack of husbandry.

I have trouble with that view, but even taking it at face value.....where do we get the idea that fighting one extreme with the other extreme is "the answer"?

Based on the bulk of threads and PM's I respond to here on R2R, ULNS seems (to put it your way) like "lack of husbandry due to trend-following".

ULNS does not seem to be desirable nor does it seem like an answer – at least not when judged from these results. (I'm sure more ideal cases are....more ideal. )

In contrast with ULNS, "high nutrients" is a natural state for a well-fed system.*

We seem to get into trouble when we fight it.

One reason for the trouble must be because "ULNS" (or nutrient depletion) is not an answer to eutrophication.

A) Nature doesn't work like this.
B) High nutrient levels ≠ eutrophication.

Tell me if this makes sense....

Eutrophcation is not a state of being. Eutrophication is a disturbance to a state of being.

A disturbance where a system is usually inundated with N, P or C....or some combo.

This inundation wrecks the former balance, no matter if it was high or low nutrient to begin with.

The "new balance" is what causes undesirable ecological changes like O2, N and P depletion, red tides, dino blooms, bubble algae outbreaks, fish kills, shellfish poisoning, etc, etc. The list is long and "coincidentally" seems to include almost all of the ills from which our aquariums suffer.

BTW, there are perfectly natural, usually seasonal, reasons that wild systems get inundated with nutrients. That's the pattern we're unintentionally emulating with all the excess nutrients we put into the environment. These "spring thaw" environments aren't always the most supportive of corals in the first place.....even in moderation they are usually "too much of a good thing". (Nutrient levels aren't necessarily the main problem trait of these areas though.)

Roughly speaking, by spiking our nutrients (our tank's "disturbance") we're cueing microbes to their "spring thaw" blooming behavior.

-Matt

* All wild reefs are well fed. The only reason some appear "ULNS like" is dilution....pure and simple. There is no lack of nutrients....even when dissolved levels are low, near to the limit of detection they are not zero and presence of a reef in this kind of location probably indicates a good supply of particulate food. "ULNS" that supports a healthy reef is at best a misnomer....maybe even a paradox. There I said it.

 

[mcarroll]

Until then, let's try getting back on topic again.

For example, I've seen recommendations to adjust nutrient levels upwards if running high alkalinity, which seems to defy Liebig's Law of the Minimum which states the rate of photosynthesis is regulated by the least available nutrient, not the most abundant.

I don't think we're breaking laws, only making sure that N or P don't become the limiting factor.

And at least so far I don't think controlling photosynthesis to be faster or slower is the goal that folks have in mind when they're going about this. Perhaps it should be though....unintended side effects are still real effects!

 

[Dana Riddle]

To get this thread back to track, after so many tangents…

My first post in this thread mentioned Liebig’s Law of the Minimum which states plant growth is limited by the least available nutrient, even when others are in abundance. It is my contention that in reasonably maintained and fed aquaria that nitrogen and phosphorous are available in quantities sufficient to maintain zooxanthellae and hence coral growth.

I found this definition of ultra-low nutrient system (ULNS) and it is:

Nitrate: 0 – 1 mg/L

Phosphate: <0.03 mg/L

I’ve got a couple of issues with this definition and had to make some assumptions. First is the way these nutrients are reported. Nitrate can be reported as NO3, or as only the nitrogen content (NO3-N). The same is true for phosphate. If we take the definition of these nutrients at face value, the actual phosphorus content is 0.009 mg/L and the nitrogen content is 0.22 mg/L.

The second point is test kits used by most hobbyists. Some do not tell how nutrients are reported (for example, NO3, or just the nitrogen content – NO3-N.) These tests report ‘ballpark numbers. This morning I checked the nitrate in the newly set up 90-gallon tank using a Hach colorimeter and the cadmium reduction method, and found the nitrate as N is 0.7 mg/L (or about 3 mg/L as nitrate, NO3.) I compared this to the results obtained with an internationally known aquarium firm, and found the nitrate (as NO3) to be, at the highest, 0.4 mg/L (and I gave it the benefit of a doubt – it was probably closer to 0.2 mg/L. So, 3 mg/L with the $1,000 instrument v. ~0.4 mg/L with the $10 test kit.

Point 3: I finally found my log book I used in coastal monitoring in Hawaii, and the testing revealed seawater on a natural reef to be nitrate (as NO3-N) at 3.6 mg/L and ortho- (reactive) phosphate as P at 0.16 mg/L. Nitrate is due to a couple of things – 1. weathering of young lava rock (geologically speaking) adds nitrate to rainwater leaching through the porous rock and 2. Leachate from septic tanks/cesspools. The phosphorus is due to septic tanks/cesspools/ lawn and golf course fertilizers. Even with these nutrient levels (checked with an expensive Hach spectrometer), the reefs were healthy with a bare minimum of algae (probably due to grazing by herbivorous fishes) and corals were colorful (I saw an astounding blood red Cyphastrea, purple and vivid green Porites, pink Pocilloporas, and so on.)

Point 4: Liebig’s Law of the Minimum. I content that evidence suggests the majority of hobbyists cannot accurately report nutrients in an aquarium (with the exception of the Hanna Checker for low range phosphorus, which I found to report results very close to those obtained with an expensive lab-grade instrument.) Nitrate is problematic – the cadmium reduction method is the only test recommended for saltwater, and even then chloride at levels in saltwater cause a negative interference (the results are low.) Organic phosphate cannot be tested for by any means I know of by the vast majority of hobbyists (unless you’ve got a block heater, specialized reagents.) Organic phosphorus, in the phosphorus cycle, is converted slowly to phosphate that can be used by plants (ortho-phosphate, or reactive phosphate.) So, nitrate and phosphorus are probably never really limiting (recall the expedition that added just iron to seawater to make phytoplankton bloom?)

Point 5: Low level nutrients lessen zoox numbers and reveal hidden coloration. Just not true, and you can test for yourself. Colorful proteins are water-soluble, so snip a brown branch off an Acropora that has colorful tips and place it in a clean contained filled with just enough distilled water to cover said branch. It might take as long as overnight for the proteins to migrate out, but usually it is just a matter of minutes. But that’s another story, and I’m off on a tangent again.

So to recap: *Some* very healthy coral ecosystems have high nutrient concentrations. Many, if not most, hobbyists do not have the means to accurately measure nutrients (especially nitrate.) Some hobbyists attempt to control phosphorus through export by algae or chemical means. These will not remove organic phosphorus which is anaerobically converted to reactive phosphate. How do we determine what gets the reactive phosphate first – corals or algae, algae or corals? Feeding will add organic nitrogen and phosphorus to the water. So, some go to great lengths to remove nutrients (which probably can’t be measured correctly) only to add nutrients back to the water. This might make sense to many, but not to me.