Skimmerless since 1997

[Reefer_NYC]

keeping it easy is the way to go!

 

[Matt Carden]

Something else I found interesting is the hypothesis that carbon dosing is doing more possible bad than good.
I am referring to the article: http://www.baharini.eu/baharini/doku.php?id=nl:makazi:theorie:koraal_holoboint#refnotes:1:note8

 

[ReefGeezer]

Very nice tank. You have a whole tank full of "skimmers".

 

[Matt Carden]

Hi.
I occasionally read comments like your PO4 recommendations above & wonder what evidence there is to back them.
0.1ppm PO4 may be fine for some, or several corals? but it is well over typical coral reef levels, & above the level typically suggested to hobbyists >> 0.03 ppm to 0.07 ppm, a level many have success with. I also wonder where in nature corals are subjected to much higher levels than 0.1ppm PO4?

You also mentioned - "The scenario you want to avoid is high nitrates and low phosphates:"

I don't know if you have any specific N-P ratio you believe one should stay below, but I've seen some misinterpret, or misrepresent what the science says on this, claiming that a P-N ratio above 10:1 is detrimental to coral health. Consider, no3 @ 2 ppm & po4 @ 0.04 ppm is a P-N ratio of 50:1.

The science mentions a threshold level of phosphate, & below this phosphate starvation can occur, exacerbated by high nitrogen levels. But if phosphate is above this threshold, the N-P ratio is unimportant.

e.g. In this paper Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates
it states the following points.

1. " We exposed corals to imbalanced N-P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals."

2. "In our experiments, a phosphate concentration of ~ 0.3 μM (0.0285 ppm) at a N/P ratio of >> 22:1 << yielded an overall healthy phenotype."

3. *** "Accordingly, it is likely that the absolute N/P ratio becomes also less critical for the proper functioning of the symbionts when phosphate concentrations exceed a vital supply threshold > 0.3 μM (0.0285 ppm), even when the symbionts are rapidly proliferating."
=================================

So if PO4 is kept at 0.03ppm or above, so corals are not starved of phosphate to begin with, N to P ratios are not a concern, at least relative to the levels hobbyists typically target.

Thoughts?

It looks like the paper you quoted has results that are contradictory to the results in the article I am referring to. These are both experiments with similar parameters and goals but with completely opposite results. There would have to be much more work done to support either conclusion. What I can say is there are examples of tanks where nutrient parameters are never checked and the system runs fine. @Paul B is an example of such a system. Is his tank heavy sps? No.

 

[Matt Carden]

We're both reading some of same research papers. 10 ppm PO4 is too high, it does interfere with calcification and at some point will kill corals. But reef aquarists have been told to keep it too low for a long time. I have two threads dealing with nuisance algae on the local forum showing PO4 levels increasing as nuiusance algae dissappeared, so it's not the direct cause of problems as is often advised. Dunn, et al, showed coral growth increase up to .5 mg/l and Richard Ross's acro dominate tank was over 1.0 mg/l at one point. His article "Chasing Numbers" I think helps put things in perspective. Research done by a group of researchers at SOuthampton University in England with corals maintained in a closed system from 2-10 years shows the problems with imbalances in the N/P ratio. Here's some links:

Nutrient enrichment can increase the susceptibility of reef corals to bleaching:

http://www.indiaenvironmentportal.org.in/files/file/Nutrient%20enrichment.pdf

Ultrastructural Biomarkers in Symbiotic Algae Reflect the Availability of Dissolved Inorganic Nutrients and Particulate Food to the Reef Coral Holobiont:

Ultrastructural Biomarkers in Symbiotic Algae Reflect the Availability of Dissolved Inorganic Nutrients and Particulate Food to the Reef Coral Holobiont

Reef building corals associated with symbiotic algae (zooxanthellae) can access environmental nutrients from different sources, most significantly via the uptake of dissolved inorganic nutrients by the algal symbiont and heterotrophic feeding of the coral host. Climate change is expected to...

www.frontiersin.org

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates

Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with din…

www.sciencedirect.com

Addendum,
I forgot to add in my response above I've been very happy with the maricultured Premium Live ROck I've gotten from GulfLiveRock.com Lots of neat stuff and especially a great source for cryptic sponges.

I know 10 ppm is way too high for corals.

I got the 17 lb. Nano package from gulfliverock.com . I think when I restart I am going to get some TBS live rock and put it in my sump so that if I get any bad guys they will be in the sump and stay there.

 

[Scrubber_steve]

It looks like the paper you quoted has results that are contradictory to the results in the article I am referring to. These are both experiments with similar parameters and goals but with completely opposite results.

Yes. But it is one paper Tim has, & others repeatedly cite.
And this is the thing with the literature, studies contradict each other, so other ** factors need to be considered before coming to any definitive conclusion.

There would have to be much more work done to support either conclusion. What I can say is there are examples of tanks where nutrient parameters are never checked and the system runs fine. @Paul B is an example of such a system. Is his tank heavy sps? No.

good point.
The evidence, for example, to support keeping P-N ratio below 10:1, when PO4 is above a threshold, doesn't stand up to scrutiny when ** so many examples of thriving tanks - especially sps dominant tanks, that run ratios at 200 - 300:1, are taken into consideration. Nothing necessarily wrong with keeping P-N ratios at or below 10:1. But to suggest above this is detrimental to corals is bad advise IMO.

I don't think Paul has any sps, but coral reeftank certainly does. He doesn't test for PO4 or NO3 any more, but he use to keep NO3 @ 4 ppm & PO4 @ 0.04 ppm, a P-N ratio of 100:1. He also doesn't bother with "any specific methods or fancy gadgets to control p04 and n03".

There is no doubting glennf's repeated success with growing sps & he targets NO3 @ 2ppm & PO4 @ 0.04 ppm, a 50:1 P-N ratio. There's plenty more.

 

[Timfish]

Hi.
I occasionally read comments like your PO4 recommendations above & wonder what evidence there is to back them.
0.1ppm PO4 may be fine for some, or several corals? but it is well over typical coral reef levels, & above the level typically suggested to hobbyists >> 0.03 ppm to 0.07 ppm, a level many have success with. I also wonder where in nature corals are subjected to much higher levels than 0.1ppm PO4?

You also mentioned - "The scenario you want to avoid is high nitrates and low phosphates:"

I don't know if you have any specific N-P ratio you believe one should stay below, but I've seen some misinterpret, or misrepresent what the science says on this, claiming that a P-N ratio above 10:1 is detrimental to coral health. Consider, no3 @ 2 ppm & po4 @ 0.04 ppm is a P-N ratio of 50:1.

The science mentions a threshold level of phosphate, & below this phosphate starvation can occur, exacerbated by high nitrogen levels. But if phosphate is above this threshold, the N-P ratio is unimportant.

e.g. In this paper Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates
it states the following points.

1. " We exposed corals to imbalanced N-P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals."

2. "In our experiments, a phosphate concentration of ~ 0.3 μM (0.0285 ppm) at a N/P ratio of >> 22:1 << yielded an overall healthy phenotype."

3. *** "Accordingly, it is likely that the absolute N/P ratio becomes also less critical for the proper functioning of the symbionts when phosphate concentrations exceed a vital supply threshold > 0.3 μM (0.0285 ppm), even when the symbionts are rapidly proliferating."
=================================

So if PO4 is kept at 0.03ppm or above, so corals are not starved of phosphate to begin with, N to P ratios are not a concern, at least relative to the levels hobbyists typically target.

Thoughts?

Regarding how much phosphate corals can tolerate and to expound on my post above I'll start with Veron's observation: "Imported nutrients are usually transported to reefs from rivers; but if there are no rivers, as with reefs remote from land masses, nutrients can only come from surface ocean circulation. Often this supply is poor, and thus the vast ocean expanses have been refered to as "nutrient deserts". The Indo-Pacific has many huge atolls in these supposed deserts which testify to the resilience of reefs, but the corals themselves may lack the lush appearance of those of more fertile waters. Many reefs have another major supply of inorganic nutrients as, under certain conditions, surface currents moving against a reef face may cause deep ocean water to be drawn to the surface. This "upwelled" water is often rich in phosphorus and other essential chemicals." J. E. N. Veron "Corals of Austrailia and the Indo-Pacific" pg 30.

A simple search shows upwelling can expose corals to ~.3 mg/l (3.0 µM) Research by Dunn, et al, shows increased linear extension and tissue growth and increased weight with by Acropora muricata at .09 mg/l, .2 mg/l and .5 mg/l PO4 with growth rates highest at .5 mg/l. RIchard Ross' system in his "Skeptical Reefkeeping 9" article had 1.24 PO4 (his system can be seen at the 3:45 mark of his video on phosphate.) From my own expereince I realized over 2 decades ago PO4 was not a major factor with problems in reef systems and stopped worrying about it.. I was not seeing high PO4 cause nuisance algae issues, quite the opposite in fact. When remediateing tanks wiht algae issues I would see inmprovet growth and apperance of corals and might also see PO4 increase as algae dissappeared.

As far as specifics for this thread it's been years since I've tested phosphates on my system in this thread but here's a video of one of my systems I got ICP results for last year showing PO4 of .9 mg/l while the PO4 level for the tapwater was 1.2 mg/l, roughly a third higher than in the system. (The ICP* results for the tapwater and system are attached.) So, I have no problem saying corals can tolerate high levels of PO4.

The problem with high nitrates to low phosphates goes beyond the levels documented by D' Angelo, Wiedeneman, Rosset and others with at Southampton. (Links to their research is in my post above, and each researcher can be searched on scholar.google.com for more reading material.) In post #16 above I posted a video by several researchers warning against high Nitrogen low Phosphorus. You can read their paper here. I also posted Fig 3 from Shantz and Burkepile, 2014 above. (They reviewed 208 experiements from 47 indipendant papers.) It shows increased nitrates are detrimental to corals inhibiting calcification. JLess than ~3 mg/l (50µM) above ambient was more than enough to negatively affect corals. A more recent paper, Claudia Pogoruetz, et al, highlights the problem of bleaching from sugars (labile DOC, carbon dosing) stimulating internal nitrification causing a phosphate deficiency in the coral.



*There is some debate about how accurate ICP results are. Like any other test I take them with a grain of salt. ICP is better than what we've had in the past but we are still a long way from being able to test dynamicly what is going on with in the coral holobiont. For an interesting discussion on the shortcomings of ICP tests I'll refer you to Richard Ross's article.

 

[Scrubber_steve]

A simple search shows upwelling can expose corals to ~.3 mg/l (3.0 µM) From my own expereince I realized over 2 decades ago PO4 was not a major factor with problems in reef systems and stopped worrying about it.. I was not seeing high PO4 cause nuisance algae issues, quite the opposite in fact. When remediateing tanks wiht algae issues I would see inmprovet growth and apperance of corals and might also see PO4 increase as algae dissappeared.

Hi Tim;
This may be the case, but my point is, recommending a phosphate level over a threshold of 0.028 ppm isn't necessary, & it can become a number chasing exercise. At that threshold PO4 is way above typical NSW levels. I live at the ocean, test NSW often, have tested water directly from Hook Island at the GBR, & PO4 never registers on a hobby kit.

The problem with high nitrates to low phosphates goes beyond the levels documented by D' Angelo, Wiedeneman, Rosset and others with at Southampton.

In the research I have read a couple of things stood out. 1. Phosphate assimilation by coral rises during heat stress.
2. Phosphate starvation can occur when nitrogen rises but this P-N ratio imbalance is only a problem in the ocean with typically super low phosphate levels to begin with.

When phosphate is at or above the threshold - 0.028 ppm, which is typical in an aquarium, P-N ratio is unimportant. With po4 at or above the threshold it is incorrect to suggest that a P-N ratio at or below 10:1 is necessary for coral health (I haven't seen you recommended this ?). At typical aquarium levels the P-N ratio is of no concern.

cheers

 

[Timfish]

@ Matt Carden "Something else I found interesting is the hypothesis that carbon dosing is doing more possible bad than good. . . "
Carbon dosing or more apropriately labile DOC can be very detrimental to corals. I would encourage you to get Forest ROhwer's "Coral Reefs in the Microbial Seas", it is an excellent introduction to the topic of DOC on reefs. One factor about labile DOC that does not seem to be very well known is cryptic sponges can remove it about 1000 x faster than the bacterioplankton it's supposed to be feeding. It's highly likely in many of the tanks where carbon dosing is being done it's having only minimal, if any, affect on the bacterioplankton as sponges are removing it too fast.

Here's a link to research looking at DOC on reefs

Here's a video by University of California also:

 

[Matt Carden]

I did get that book. I got about half way through then got distracted by all the pretty pictures in @najer twins thread. I will get to finishing it eventually. Tank is still a month or 2 from being salty so I have time.

I did find that interesting that all these reefers following something that isn't just not doing anything but is actually detrimental to their balanced ecosystems.

 

[najer]

I did get that book. I got about half way through then got distracted by all the pretty pictures in @najer twins thread. I will get to finishing it eventually. Tank is still a month or 2 from being salty so I have time.

I did find that interesting that all these reefers following something that isn't just not doing anything but is actually detrimental to their balanced ecosystems.

Lol, thanks.

 

[Timfish]

Some of this I've posted above but here are more complete lists of research I posted on RevTree's "Coral Death" thread.




https://ars.els-cdn.com/content/image/1-s2.0-S0966842X1500075X-mmc1.mp4

See also Forest Rohwer's book "Coral Reefs in the Microbial Seas". Kim Ritchie and her work with Coral Diseases. Jasper de Goeij's papers on cryptic sponges. Rebeca Thurber's research with coral bacteria. Andeas Haas' work on DOC, microbes, corals and algae. Finally D' Angelo and Wiedenman's work with nutrients and corals.

 

[Timfish]

. . . With po4 at or above the threshold it is incorrect to suggest that a P-N ratio at or below 10:1 is necessary for coral health (I haven't seen you recommended this ?). At typical aquarium levels the P-N ratio is of no concern. . . .

First of all I most certainly have not said N-P ratios above 10-1 are detrimental anywhere. It would be pretty stupid as I am on the record using Southampton's results.

I am curious where you heard that ratio of 10-1 N-P being bad? Thurber, et al, did find ratios close to your supposed 10-1 N-P did increase disease incidence on a reef. However, I think it's important to keep in mind that was the result of fertilizer being dosed in addition to the plankton the reef was receiving it. Very different than the controlled conditions used by Southampton. (For refference Delbeek and Sprung on pg 377 and 378 of "The Reef Aquarium" V. III discuss plankton on reefs and give numbers of 2 gm to 5 gm dry weight per 100 gallons daily.)

. . . it can become a number chasing exercise. . . .

I certainly agree on not chasing numbers. I was curious and went back to when I first started using that phrase and it was almost 7 years ago. And here's a qoute of mine from 9 years ago:

"Some people advocate frequent testing and some people (myself) are more lax and use the ol' eyeball, I would point out that corals can over time acclimate to conditions that will kill new corals so at least periodic testing is suggested once you are familiar with your tanks moods."

. . . but my point is, recommending a phosphate level over a threshold of 0.028 ppm isn't necessary, & it can become a number chasing exercise. At that threshold PO4 is way above typical NSW levels. I live at the ocean, test NSW often, have tested water directly from Hook Island at the GBR, & PO4 never registers on a hobby kit.

In the research I have read a couple of things stood out. 1. Phosphate assimilation by coral rises during heat stress.
. . .

10 years ago Delbeek wrote this:
"Our crystal-clear aquaria do not come close to the nutrient loads that swirl around natural reefs. And so when we create low-nutrient water conditions, we still have to deal with the rest of a much more complex puzzle. Much like those who run their aquarium water temperature close to the thermal maximums of corals walk a narrow tight rope, I can't help but think that low-nutrient aquariums may be headed down a similar path." Charles Delbeck, Coral Nov/Dec 2010, pg 127

It's not at all surprising to me you have very little PO4 in the reef close to you. Kleypas, et al, 1999 gives minimums and maximums and some reefs are very low. Average PO4 is ~.012 mg/l (.13 µM). Maximum given by Kleypas is ~.0512 mg/l (.54 µM). Sooooo, I have to disagree with your assertion .028 mg/l is " is way above typical NSW levels"

If we only had to deal with the risk of uric acid crystals forming and rupturing coral cell walls it really wouldn't bother me to say stick to .028 like you seem to be saying. Keeping PO4 low can be done for years. D' Angelo and Wiedenmann at Southampton University set up a very typical reef system and maintained it for years before they started running thier experiements. (I've posted several of thier papers already but here's thier paper where they initially describe thier system.) But as you've read when temperatures rise PO4 demand rises also. One of the biggest problems I see is AC failure. Keeping PO4 higher than the threashold identified by Southampton reduces the risk of bleaching corals due to a phosphate deficiency should aquarium temperatures rise unexpectidly.

. . . 2. Phosphate starvation can occur when nitrogen rises but this P-N ratio imbalance is only a problem in the ocean with typically super low phosphate levels to begin with.

When phosphate is at or above the threshold - 0.028 ppm, which is typical in an aquarium, P-N ratio is unimportant. . . .

I guess you didn't read all the papers done by Southampton I posted. Thier experiments were done on corals maintained in a typical reef setup. Not conducted on corals in situ. Thier research applies just as much to corals maintained in our systems as much, if not more so, than corals on reefs.

 

[living_tribunal]

Hi.
I occasionally read comments like your PO4 recommendations above & wonder what evidence there is to back them.
0.1ppm PO4 may be fine for some, or several corals? but it is well over typical coral reef levels, & above the level typically suggested to hobbyists >> 0.03 ppm to 0.07 ppm, a level many have success with. I also wonder where in nature corals are subjected to much higher levels than 0.1ppm PO4?

You also mentioned - "The scenario you want to avoid is high nitrates and low phosphates:"

I don't know if you have any specific N-P ratio you believe one should stay below, but I've seen some misinterpret, or misrepresent what the science says on this, claiming that a P-N ratio above 10:1 is detrimental to coral health. Consider, no3 @ 2 ppm & po4 @ 0.04 ppm is a P-N ratio of 50:1.

The science mentions a threshold level of phosphate, & below this phosphate starvation can occur, exacerbated by high nitrogen levels. But if phosphate is above this threshold, the N-P ratio is unimportant.

e.g. In this paper Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates
it states the following points.

1. " We exposed corals to imbalanced N-P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals."

2. "In our experiments, a phosphate concentration of ~ 0.3 μM (0.0285 ppm) at a N/P ratio of >> 22:1 << yielded an overall healthy phenotype."

3. *** "Accordingly, it is likely that the absolute N/P ratio becomes also less critical for the proper functioning of the symbionts when phosphate concentrations exceed a vital supply threshold > 0.3 μM (0.0285 ppm), even when the symbionts are rapidly proliferating."
=================================

So if PO4 is kept at 0.03ppm or above, so corals are not starved of phosphate to begin with, N to P ratios are not a concern, at least relative to the levels hobbyists typically target.

Thoughts?

You always ask for the evidence when you cite it yourself.

Aside from the articles @Timfish and I have posted, nearly all research posted from those in the field indicates corals do calcify (by volume) significantly faster at higher phosphate levels with absolutely no impact on zoox efficiency, polyp extension, or tissue growth.

You counter published, credentialed, and repeatable experiments in an aquarium environment with nothing other than anecdotal hyperbole and conjecture. There is more substance in arguments made by flat earth proponents....

If corals can grow faster at higher P levels as we can state with near 100% certainty, and we also know that high N stunts growth (no, the slower growth is not from just being a limiting factor for algae that in turn consumes the phosphate causing the deficiency), and we finally know that every health parameter for corals under high p is nearly identical to that when parameters are replete, then why are you against high P?

Tim never mentioned ratios, I did, and I only stated it once as natural reefs are between 5-7x N/P. The ratio is not the main point we’re trying to communicate. It’s the fact that higher p at worst leads to coral health being neutral to replete and at best making coral grow faster.

Just curious, you seem to aggressively oppose the very valid science behind the methods Tim posted. What is the specific point you’re trying to make? Is it that higher P does not lead to faster coral growth?

 

[Scrubber_steve]

First of all I most certainly have not said N-P ratios above 10-1 are detrimental anywhere. It would be pretty stupid as I am on the record using Southampton's results.

OK Tim, I tried to send you a private message to discuss the points you've raised by quoting me. This wasn't possible as it seems you have placed me on your ignore list, for some reason? That's very interesting, & also perplexing as you quote me here, looking for interaction.

In any case, I will respond in part only to the points you have raised.

Firstly Tim; you wrote " First of all I most certainly have not said N-P ratios above 10-1 are detrimental anywhere. It would be pretty stupid as I am on the record using Southampton's results."

Hmmmm ?
I ask you Tim to go back & read my extract you quoted .

This is what you quoted me saying -

Scrubber_steve said:
". . . With po4 at or above the threshold it is incorrect to suggest that a P-N ratio at or below 10:1 is necessary for coral health
(I haven't seen you recommended this ?). At typical aquarium levels the P-N ratio is of no concern. . . ."

Note the part Tim where I said "(I haven't seen you recommended this ?)"

No worries Tim.

Secondly Tim; you are "curious where heard that ratio of 10-1 N-P being bad".

Here's one person Tim, who cites all the same papers you do - quote "Nitrate should only be anywhere from 5 to 10 times higher than your phosphate level to negate any issues with your coral." That's Saltyreef saying that. You may have had some personal communications with him, as you have with Living tribunal, who also curiously cites all the same papers you do Tim. Read the thread Tim, its enlightening. @Randy Holmes-Farley makes some comments regarding the ratio.

Speaking of Living tribunal, here's a couple of his quotes - "It's less about your absolute phosphate level and more about your N/P ratio. Current reefs (real world reefs) that are maintaining very fast growth have an N/P of 4-5x. Anything under 10-14x will be great. Over 20x is when you see less growth."

Lifving T's referring to values in an aquarium, & I say what he says isn’t correct as do many others, including @jda .

Here's a bit more from Living T - "To summarize it concisely, high nitrate and high phosphate at a N/P range of 5-10x is the most optimal for coral health and growth."

Again, I say what he says isnt right as do many others, especially when referring to aquaria.

Now @Timfish, here's a thread you & your mates can go argue your case in with @Lasse , @Randy Holmes-Farley, & who ever else bothers to take the time.
Nutrient´s ratio - of importance or not?
what I think is written in that thread here

 

[living_tribunal]

Someone hates scientific research and phosphates.

I believe that introducing new science is important, as is approaching its efficacy skeptically, for advancing this hobby to new levels.

Just ten years ago, it was the common talking point that zero phosphates was preferred which ultimately proved to be wrong.

A healthy debate is always crucial in determining whether something is or could potentially be applicable in a niche situation. Rebuking science with opposing science, and even compelling anecdotal reports, is the fastest way to advancing a groups understanding.

Choosing to actively insult those who simply introduce new topics and attempt to shut down a potentially disruptive conversation without any substantive rebuke does not help propel our understanding of this rather tricky hobby. Saying proposed science is simply “crap” and dropping a thread link which contains no hard data to deem said science as “crap” does not move the conversation nor our understanding a step further. It halts it in its tracks. I always welcome all enlightening material, from respectable sources, from any reefer, as long as the substance and logic are sound.

We all choose our own paths in this hobby. We aren’t idiots. Everyone here actively evaluates new concepts and whether they are appropriate for our systems, we don’t need to have someone barricade which information is accessible vs. what should be hidden.

 

[living_tribunal]

First of all I most certainly have not said N-P ratios above 10-1 are detrimental anywhere. It would be pretty stupid as I am on the record using Southampton's results.

I am curious where you heard that ratio of 10-1 N-P being bad? Thurber, et al, did find ratios close to your supposed 10-1 N-P did increase disease incidence on a reef. However, I think it's important to keep in mind that was the result of fertilizer being dosed in addition to the plankton the reef was receiving it. Very different than the controlled conditions used by Southampton. (For refference Delbeek and Sprung on pg 377 and 378 of "The Reef Aquarium" V. III discuss plankton on reefs and give numbers of 2 gm to 5 gm dry weight per 100 gallons daily.)




I certainly agree on not chasing numbers. I was curious and went back to when I first started using that phrase and it was almost 7 years ago. And here's a qoute of mine from 9 years ago:

"Some people advocate frequent testing and some people (myself) are more lax and use the ol' eyeball, I would point out that corals can over time acclimate to conditions that will kill new corals so at least periodic testing is suggested once you are familiar with your tanks moods."



10 years ago Delbeek wrote this:
"Our crystal-clear aquaria do not come close to the nutrient loads that swirl around natural reefs. And so when we create low-nutrient water conditions, we still have to deal with the rest of a much more complex puzzle. Much like those who run their aquarium water temperature close to the thermal maximums of corals walk a narrow tight rope, I can't help but think that low-nutrient aquariums may be headed down a similar path." Charles Delbeck, Coral Nov/Dec 2010, pg 127

It's not at all surprising to me you have very little PO4 in the reef close to you. Kleypas, et al, 1999 gives minimums and maximums and some reefs are very low. Average PO4 is ~.012 mg/l (.13 µM). Maximum given by Kleypas is ~.0512 mg/l (.54 µM). Sooooo, I have to disagree with your assertion .028 mg/l is " is way above typical NSW levels"

If we only had to deal with the risk of uric acid crystals forming and rupturing coral cell walls it really wouldn't bother me to say stick to .028 like you seem to be saying. Keeping PO4 low can be done for years. D' Angelo and Wiedenmann at Southampton University set up a very typical reef system and maintained it for years before they started running thier experiements. (I've posted several of thier papers already but here's thier paper where they initially describe thier system.) But as you've read when temperatures rise PO4 demand rises also. One of the biggest problems I see is AC failure. Keeping PO4 higher than the threashold identified by Southampton reduces the risk of bleaching corals due to a phosphate deficiency should aquarium temperatures rise unexpectidly.




I guess you didn't read all the papers done by Southampton I posted. Thier experiments were done on corals maintained in a typical reef setup. Not conducted on corals in situ. Thier research applies just as much to corals maintained in our systems as much, if not more so, than corals on reefs.

One additional item to note is that potential N enrichment stunting coral growth does not arise from micro algae simply growing and absorbing the available phosphate, it also interferes with the symbiotic process of the coral passing trace nitrate to the zooxanthallae and receiving sugars, aminos, and carbs in return.

To frame this concept in a way without citing numbers, higher phosphates can only aid coral health, ease of maintaining optimal health in a closed system, prevent uric acid crystals, maintain the highest zoox efficiencies, etc until the point that the higher levels promote nuisance bacterial and algae levels.

Running uln or near “perfect natural reef” levels is indeed walking a tight rope. When the demand for one parameter, and its associated health benefits, heavily skew one way, why risk it?

 

[Matt Carden]

I just read Steve Tyree's CMAT volume 2. He stated that during photosynthesis algae release photosynthate which will fuel bacteria growth. Because of this He advises that aquarist don't use Algae Turf Scrubber for nutrient export without the aid of a Skimmer to remove the excess bacteria growth. I was planning on incorporating an ATS into my new sump design until I read this.

 

[Timfish]

OK Tim, I tried to send you a private message to discuss the points you've raised by quoting me. This wasn't possible as it seems you have placed me on your ignore list, for some reason? That's very interesting, & also perplexing as you quote me here, looking for interaction. . . .

Curious, I haven't marked anybody to be ignored. But I don't see why this conversation has to be conducted in private either. It seems to me just about anybody reading this would benefit from this discusion of the science.

It will take a week or so for me to look at your's and other posts you want me look at and get back with you.

 

[LRT]

Hi Tim I have one question.
Are you using natural light to light your reef?
I didn't notice any lights hanging in the video you posted in top down thread.