Are elevated nutrients a problem, or not?

[Tuna Melt]

Here's a topical read that was published August 23rd, 2023: https://www.nature.com/articles/s41586-023-06442-5#:~:text=Corals feed on symbionts to,through feeding on the symbionts.

The Reef builders summary: https://reefbuilders.com/2023/08/24/study-reveals-how-corals-gain-n-and-p-in-darwins-paradox/

Long story short, corals need P & N for growth. They can feed on particulates, aminos or uptake ammonia, however they cannot directly uptake NO3 or PO4. Luckily the zooxanthellae can. So when particulates foods are absent, the coral consume their own zooxanthellae to get their fix of P & N. In a PO4&NO3 depleted system, the zooxanthellae can't reproduce fast enough and the coral effectively cannibalizes its self. In the study they did, they found coral growth in a nutrient limited system stagnated around 50 days and these coral lost more than half of their symbiont zooxanthellae. By contrast, in the nutrient-replete system, the corals grew and calcified at an exponential rate and symbiont density remained constant.

In the study:
Nutrient Rich = [NO3] ≈ 12 µM, [PO4] ≈ 3 µM
Nutrient Limited = [NO3] ≈ 0.7 µM & [PO4] ≈ 0.13

What was interesting to me was that in the study PO4 of 0.13 is "limited". Think most would agree NO3 of 0.7 is low, (currently struggling with that myself) but I imagine many would consider PO4 of 0.13 to be standard, maybe even high.

 

[jda]

Like many RB articles, they miss a lot. Growing DOES need carbon energy from the zoox and N and P. N and P do not have energy. I would suggest reading the article, if you can, since RB does not often get many things right.

What was weird about that article to me is that hosts can usually recycle N and P to maintain. There is a bit of loss, so this cannot happen forever, but it should be happening for more than 50 days. I don't know how to reconcile this with other studies.

I do not agree that .7 or no3 is low - it likely does not matter at all if ammonium or nitrite are present or the coral is assimilating live things at any rate.

Bacteria in the slime coats is probably the best way for most true coral (stonies) to get N, P and C through assimilation. The largest issues with a lot of these studies is similar to brand new tanks where this is not always happening.

 

[YOYOYOReefer]

I could never grow lips frags into colonies in ultra low nutrient conditions , not very quickly. However the sticks like those conditions and generally color up best, but I think growth is more about the lighting And keeping alk stable. I keep fish like anthias and mini lions in my reef so have to feed heavily ,sps do fine but the lps tend to really grow out . I also like the lp s’more so that’s why .


I never tried a tank with dead rock and frags, that Might play a huge factor maturity of the tank and rock

 

[Tuna Melt]

Like many RB articles, they miss a lot. Growing DOES need carbon energy from the zoox and N and P. N and P do not have energy. I would suggest reading the article, if you can, since RB does not often get many things right.

What was weird about that article to me is that hosts can usually recycle N and P to maintain. There is a bit of loss, so this cannot happen forever, but it should be happening for more than 50 days. I don't know how to reconcile this with other studies.

I do not agree that .7 or no3 is low - it likely does not matter at all if ammonium or nitrite are present or the coral is assimilating live things at any rate.

Bacteria in the slime coats is probably the best way for most true coral (stonies) to get N, P and C through assimilation. The largest issues with a lot of these studies is similar to brand new tanks where this is not always happening.

Agreed that if the coral are getting these nutrients in other ways than its a non issue. In the study they tried to isolate the effects by removing particulates and living food with 10m micron socks and UVs. Here are the results:

 

[Tuna Melt]

*sorry accidentally double posted*

 

[Tuna Melt]

Agreed that if the coral are getting these nutrients in other ways than its a non issue. In the study they tried to isolate the effects by removing particulates and living food with 10m micron socks and UVs. Here are the results:

I guess my point is I can't test the particulate food in the water column or the bacteria in the slime coats . So how do I know I'm not depriving my coral in a low nutrient system in light of this study other than just eye balling it?

 

[Dan_P]

Here's a topical read that was published August 23rd, 2023: https://www.nature.com/articles/s41586-023-06442-5#:~:text=Corals feed on symbionts to,through feeding on the symbionts.

The Reef builders summary: https://reefbuilders.com/2023/08/24/study-reveals-how-corals-gain-n-and-p-in-darwins-paradox/

Long story short, corals need P & N for growth. They can feed on particulates, aminos or uptake ammonia, however they cannot directly uptake NO3 or PO4. Luckily the zooxanthellae can. So when particulates foods are absent, the coral consume their own zooxanthellae to get their fix of P & N. In a PO4&NO3 depleted system, the zooxanthellae can't reproduce fast enough and the coral effectively cannibalizes its self. In the study they did, they found coral growth in a nutrient limited system stagnated around 50 days and these coral lost more than half of their symbiont zooxanthellae. By contrast, in the nutrient-replete system, the corals grew and calcified at an exponential rate and symbiont density remained constant.

In the study:
Nutrient Rich = [NO3] ≈ 12 µM, [PO4] ≈ 3 µM
Nutrient Limited = [NO3] ≈ 0.7 µM & [PO4] ≈ 0.13

What was interesting to me was that in the study PO4 of 0.13 is "limited". Think most would agree NO3 of 0.7 is low, (currently struggling with that myself) but I imagine many would consider PO4 of 0.13 to be standard, maybe even high.

I think that 0.13 micro molar PO4 is equivalent to about 13 ppb or 0.013 ppm

 

[Koty]

Here's a topical read that was published August 23rd, 2023: https://www.nature.com/articles/s41586-023-06442-5#:~:text=Corals feed on symbionts to,through feeding on the symbionts.

The Reef builders summary: https://reefbuilders.com/2023/08/24/study-reveals-how-corals-gain-n-and-p-in-darwins-paradox/

Long story short, corals need P & N for growth. They can feed on particulates, aminos or uptake ammonia, however they cannot directly uptake NO3 or PO4. Luckily the zooxanthellae can. So when particulates foods are absent, the coral consume their own zooxanthellae to get their fix of P & N. In a PO4&NO3 depleted system, the zooxanthellae can't reproduce fast enough and the coral effectively cannibalizes its self. In the study they did, they found coral growth in a nutrient limited system stagnated around 50 days and these coral lost more than half of their symbiont zooxanthellae. By contrast, in the nutrient-replete system, the corals grew and calcified at an exponential rate and symbiont density remained constant.

In the study:
Nutrient Rich = [NO3] ≈ 12 µM, [PO4] ≈ 3 µM
Nutrient Limited = [NO3] ≈ 0.7 µM & [PO4] ≈ 0.13

What was interesting to me was that in the study PO4 of 0.13 is "limited". Think most would agree NO3 of 0.7 is low, (currently struggling with that myself) but I imagine many would consider PO4 of 0.13 to be standard, maybe even high.

 

[Koty]

Is it OK to publish R^2 (linear regression) analysis for nonlinear plots?

 

[Tuna Melt]

Ah, that makes more sense!

 

[Superlightman]

Here's a topical read that was published August 23rd, 2023: https://www.nature.com/articles/s41586-023-06442-5#:~:text=Corals feed on symbionts to,through feeding on the symbionts.

The Reef builders summary: https://reefbuilders.com/2023/08/24/study-reveals-how-corals-gain-n-and-p-in-darwins-paradox/

Long story short, corals need P & N for growth. They can feed on particulates, aminos or uptake ammonia, however they cannot directly uptake NO3 or PO4. Luckily the zooxanthellae can. So when particulates foods are absent, the coral consume their own zooxanthellae to get their fix of P & N. In a PO4&NO3 depleted system, the zooxanthellae can't reproduce fast enough and the coral effectively cannibalizes its self. In the study they did, they found coral growth in a nutrient limited system stagnated around 50 days and these coral lost more than half of their symbiont zooxanthellae. By contrast, in the nutrient-replete system, the corals grew and calcified at an exponential rate and symbiont density remained constant.

In the study:
Nutrient Rich = [NO3] ≈ 12 µM, [PO4] ≈ 3 µM
Nutrient Limited = [NO3] ≈ 0.7 µM & [PO4] ≈ 0.13

What was interesting to me was that in the study PO4 of 0.13 is "limited". Think most would agree NO3 of 0.7 is low, (currently struggling with that myself) but I imagine many would consider PO4 of 0.13 to be standard, maybe even high.

@Hans-Werner

 

[biom]

Is it OK to publish R^2 (linear regression) analysis for nonlinear plots?

No, it is not, R-squared is invalid for nonlinear regression models. BUT you can't tell from the graph if there is a linear or nonlinear regression, you can have a curve and still have a linear regression model (I am not saying this is the case here I'll need at least residual plots to check ). But this wrongful usage of R squared is quite common in biology, biochemistry and ecology papers even at that high level journals.

 

[Jedi1199]

In my experience so far, I feel that lighting is far more important to SPS growth than nutrient levels.

In my old 55g, I had a hard time keeping any SPS for more than a month or 2. This is despite regular water changes and testing of parameters. Once I switched from cheap lights to higher quality lights, the SPS that were shrinking, recovered and took off.

Then came the tank upgrade. I went from a 55g to 135g. I doubled my lighting. (was running 2 Kessil a360x tuna blues on the 55 and now have 4 over the 135.)

You would think that 4 would be more than enough right? I am not so sure... I have lost most of my SPS corals in the last year since the upgrade. ALL of the LPS and softies are thriving.

Do we take from this that lighting is the issue? IDK.. My husbandry on this tank had changed a lot due to work and available time. Off the top of my head I would say it has been at least 3 months since I last tested my water. (probably more than that) So is it lights or nutrients? Better lights worked when I was testing regularly.. I have lost stuff since the upgrade even though my actual par levels are better.. So is it lights? Nutrients? a combination of both?

Is my issue a matter of "new tank syndrome"? Is the flow incorrect? Are the corals not placed high enough? Is my filtration not sufficient? ect ect...


My opinion is that there is no singe factor in most builds that contributes to either die off or explosion. Most commonly it is a multiple of issues that need to be identified and remedied in order to achieve the results we all are after.

 

[biom]

In my experience so far, I feel that lighting is far more important to SPS growth than nutrient levels.

In my old 55g, I had a hard time keeping any SPS for more than a month or 2. This is despite regular water changes and testing of parameters. Once I switched from cheap lights to higher quality lights, the SPS that were shrinking, recovered and took off.

Then came the tank upgrade. I went from a 55g to 135g. I doubled my lighting. (was running 2 Kessil a360x tuna blues on the 55 and now have 4 over the 135.)

You would think that 4 would be more than enough right? I am not so sure... I have lost most of my SPS corals in the last year since the upgrade. ALL of the LPS and softies are thriving.

Do we take from this that lighting is the issue? IDK.. My husbandry on this tank had changed a lot due to work and available time. Off the top of my head I would say it has been at least 3 months since I last tested my water. (probably more than that) So is it lights or nutrients? Better lights worked when I was testing regularly.. I have lost stuff since the upgrade even though my actual par levels are better.. So is it lights? Nutrients? a combination of both?

Is my issue a matter of "new tank syndrome"? Is the flow incorrect? Are the corals not placed high enough? Is my filtration not sufficient? ect ect...


My opinion is that there is no singe factor in most builds that contributes to either die off or explosion. Most commonly it is a multiple of issues that need to be identified and remedied in order to achieve the results we all are after.

Fully agree here, especially if we are talking about SPS corals. Light available is critical for their growth. Almost everyone is testing nitrate and phosphate but how many of us are actually (properly )measuring light? Many of us rely on vendors claims which are sometimes not really correct or are not applicable for our tank's conditions.

 

[tedfisher496]

Elevated nutrients are one of the most talked about issues in reefkeeping, with folks on all sides of the issue.

There is, however, no simple answer to the title question (IMO).

I thought I'd start a thread for a wide ranging discussion of this issue, and to gather many of the bits of data and anecdotes and comments in one place.

I'll start off with a few ideas to provide some background and ideas to debate.

1. It is clear that there are great reef tanks that most hobbyists admire with nutrients (nitrate and phosphate, particularly) ranging from low levels (say, less than 2 ppm nitrate and 0.01 ppm phosphate) up to quite high levels (>1 ppm phosphate and >100 ppm nitrate).

2. It is clear that there are reef tanks overrun with bryopsis, valonia, green hair algae, caulerpa, dinos, cyano, or other problems at nearly any of the values mentioned in 1.

3. Scientific studies on the effects of elevated nutrients on growth of hard corals are mixed. In some studies they thrive. In some studies they do not. In some studies, some growth forms (e.g., encrusting) are decreased and others (e.g., linear growth) of the same coral are increased. In most study cases, these are not getting the natural particulate foods they would get in the wild, and how much of what particulate foods they get in aquaria likely varies greatly based on husbandry techniques used.

4. Scientific studies on elevated nutrients in the ocean often suggest that hard corals decline and other organisms take over. This result is, of course, not due to solely to effects of nutrients on corals, but to effects on competing organisms as well.

Since a reef aquarium is, in some ways, a small microcosm of the real ocean, I think point 4 should not be dismissed, even knowing that point 1 is valid.

Perhaps point 1 is only valid for elevated nutrients if there are other aspects of the aquarium that allow hard corals to thrive. For example, herbivores to control algae.

Here, for example, is a recent analysis relating to hard corals in the ocean with elevated nutrients:

A new perspective of nutrient management of subtropical coastal stress-tolerant scleractinian coral communities

A new perspective of nutrient management of subtropical coastal stress-tolerant scleractinian coral communities

Elevated nutrients decrease the healthy status of coral communities, which can be stressful on reef corals, always resulting in decreased live sclerac…

www.sciencedirect.com

from it:

Elevated nutrients decrease the healthy status of coral communities, which can be stressful on reef corals, always resulting in decreased live scleractinian coral cover (LSCC).

I wish i had elevated no3 and p04. Im constantly battling low or zero in my 25 gallon.

 

[jda]

I also would rather have a best-of-breed light and substandard parameters rather than perfect parameters and a substandard light.

Two things come to mind... most importantly, the two are not mutally exclusive, so get them both right, or close to right.

Second, most lights now-a-days are substandard to some corals with lack of true UV and IR and folks wanting to find a PAR chart and provide just the bare minimum. Another reason to get the rest of it right too. You can always add more light or different kinds of light, but what you are doing today could make it really hard to make wholesale changes to your water chemistry later on... especially if you let a massive amount of po4 compounds bind to your rocks and sand.

 

[Mppp]

When my tank levels were high, by that i mean nitrate at 25 ppm and phosphate at .9 ppm my corals seemed to be ok. My BTA looked very happy. Once I started carbon dosing that's when everything looked amazing . My zoas exploded and grew like crazy. Now i have the levels low I've cut back on the dosing and everything looks hungry. My BTA is always fully open but his tentacles are short and its mouth is always open. I have a 29 gal nano mostly lps. I do biweekly water changes. I feed the corals reef roids once a week and my BTA twice a week with Mysis. the clowns once a day.

My numbers are quite close to yours 21 ppm and .09 ppm phosphate. I occasionally use nopox and am curious what you mean things exploded when you used it, did your numbers drop so corals are happier? I've noticed the same with my BTA when I consistently use nopox more than a week or so straight and my trachphyllia doesn't seem to appreciate it either. Thanks for input!

 

[Thales]

I expect he is likely to post to this thread, but what was your take away from his video?

Hey Randy! If you expect I would reply, I must!

I chased a lot of numbers in a lot of tanks for a long time and had varying degrees of success. I watched a lot of people do the same. I watched a lot of people do a lot more work than I did, and some had more suceess and some had less, which led me to think that doing more to a tank doesn't mean that it will be 'better'. No matter what people do, it seems some corals do well in their system and some don't.

I think reef tanks are complex systems and that it can be really hard to pin down what does and doesn't make a difference in coral health, espically because we tend to try to lump all coarls into one bin.

One throughline to my reefing approach as been to 'stabilize' the system and then try to leave it alone as much as possibe. Sometimes that has led me to being overly lazy or the realities of life distracted me, which has led to some issues. However, when I keep up on most stuff, when I am paying attention so that whatever I have in place to keep the reef going is working and doing what it is supposed to - and when I am not changing chemistry or majorly tweaking anything at all in the system...when I let it all ride and do its thing, the corals seem to grow better, faster, and be more colorful.

I think flow is really important, and think it equally important that it changes intensity and style over the course of the day. This tends to help mix any dead spots, and gives the more sensitive corals a break from high flow.

I have also noticed that it sometimes seems to talk 3-8 months for my reefs to recover from something traumatic. Earlier this year I had some pathogen causing RTN, so I treated the tank, and only now does the display seem to be firing on all cylinders and the system seems robust. I was just gone for 3 weeks and the alk droped from around 9 to around 7 for 2 two of those weeks (and took a week to come back up after I got home) and none of the corals seemed to care, the sps are growing like mad.

I have also noticed that it takes some corals a long time to adapt to a particular system. Like 3-8 months or more. I think this may be responsible for some of the correlation/causation confusion we see in the hobby; if a coral has been doing poorly for a while, and the reefer changes something, it is very easy to say that change made the difference, when it really could just be the coral finally adapting.

I have seen no compelling evidence that low nutrients impact algae, and, given how algae live, I don't think that idea makes much sense at its core. I also don't see much compelling for the idea that you can grow algae in one part of the system to limit algae in another part of the system. I think herbivores, and manual removal/cropping are practical solutions to a lot of algal problems. I think most and dino and cyano issues burn themselves out, and that letting them do that stabilizes the system, and makes it more robust over time.

All that said, I have not tested Po4 and Nitrate since March (Po4 .62 & No3 35 which was up from the previous time I tested in October (Po4 34 No3 14). I keep thinking I should test, but it feels like make work, which I am trying to avoid at this point in my life. I don't do ICP often, and when I do test at home I usually use a Hach DR890, but I got some hanna checkers so I could more easily be on the same page of most of the hobby (though that might require me to actually do some testing).

In general, I think mixing testing methodologies will make you insane, so I say pick one and stick with it (and be realistic about the numbers because there is so much room for error and variability). I tried for a long time to compare methods of testing salinity (Milwaukee, Misco, Floating, Refracto, Conductivity, etc) and nearly went bonkers. Now use the apex conductivity probes in my system for trending, a veegee because it is fast for quick checks, and a Tropic Marin floating if I want to feel more precise (I should calibrate it but ugh). I like ICP every once and a while to check for anything obviously out of whack that could be killing my tank. I currently don't do biomics testing because I don't think there is much that is actionable in that realm yet. Again, kudos for folks that like to try to dig into those numbers.

In 2019 I plumbed the Secret Home Lab into the display system because volume impacts stability, and taking care of two systems was making me nuts. Yes, there are downsides to this but there are downsides to independent systems as well. In the Lab I have been growing coarls from embryos since 2020 (they are large now and I hope they will spawn this season) and I spawned A. mil last Nov/Dec and those babies are growing nicely. I am currently hoping for some gravid A. sar to arrive next week to spawn in early Nov (and hope for not a split spawn, so tiring!).

In the display (Mixed - LPS, SPS, NPS) some 'hard to keep sps' are doing fine and some are doing less fine. The pearl berry had AEFW, and seems to be perking up, and the Paletta Pink Tip is going gang busters. The Hawkins won't stop growing. I think that is all of the fancy names I remember.

So what is my point in regards to nutrients? I agree with you, there is no simple answer. I do know that I am much more interested in making my display beautiful to my eye, and playing with baby coral, than I am in tracking numbers and dosing lots of stuff. But that is me, and I fully appreciate folks that have the time and energy and money to mess around in that arena. I do think that a 'stable system' seems like it is very important in regards to long term care, and that whatever your philosophy around nutrients may be, keeping the system robustly stable seems important. I think a lot of available reefing methods produce good tanks, and help turn around bad tanks, not because of anything intrinsic to the method, but because they get people to pay attention to the system as a whole and help keep it stable.

Thanks for the push that helped me to summarize my current reefing philosophy, clearly I had this brewing in the back of my brain. Sorry if it is kind of off topic.

Here are two pics of my display I just took after being home from being gone for about 3 weeks. The right side had a major remodel yesterday, so sorry if it looks not grown in. Photographed under SKY lights, one set to photo mode at 50% brightness, and the other set to custom blues off, white and amber 100%shot on iPhone 13 with the Aquarium Cam app on auto. Beats me, I don’t see color well, so maybe they look like the tank actually looks. I am tired.

 

[Reefahholic]

I’ve been running elevated nutrients for lingering Dino’s this year. Elevated is kinda subjective, because everyone seems to have different opinions as to what elevated actually is, so I will give you mine.

Elevated to me is above 0.3 ppm. I ran up near or at 0.4 ppm for a while. Here’s what I noticed.

1. My Miyagi tort and other corals became very brittle.

2. Acro’s will brown out. It took me a few times to get it there, but I finally got up to 0.4 w/o them browning out. The corals need to get used to that much PO4 if they were previously at much lower levels. Maybe increase by .01 every other day and skip a week.

3. My rocks get super clean with higher PO4 levels, but once you go over the limit, you will start to grow and feed undesirable algae.

4. Some corals seemed to really like it, but others didn’t. Growth was split.

5. I think the ideal PO4 level is between .06 to 0.15 with NO3 being at or around 100:1 I’ve had really good luck there and the least amount of issues, but every system is different. That is no joke. I’ve experienced that firsthand.


Phosphate is so important, but sometimes it’s hard to get just right. It takes experience in many different situations, and good data to pin it down. Very similar to PAR and spectrum.

If you really want to jack up a tank let the phosphate become completely depleted.

 

[dstockwell]

My tank is about 14 months old and my softies,GSP, pulsating xenia, devils hand, zoas, and gorgonians all look great. But since I use DI water because I get for nothing from the plant, my PO4 is 2.0 and NO3 20. I have tried twice to keep birds-nest and failed at both. I have lost hammer and torch so unless I change what i am doing, which isn't likely I can be happy with softies.