Randy’s Thoughts on Nutrient Target Ranges

[LiquidSpace]

@Randy Holmes-Farley

I’m pretty sure this is the stupidest question I have asked in all my time on R2R, but here it goes.

My aquarium has been running for almost 7 months with no lights. It’s 200 gallons. Phosphates are at 0.08 and nitrates are at 17.5 ppm. Nitrate has increased by 5.0 ppm in a month. This is with 2 gallon auto water changes per day, which I have bumped up to 4 gallons.

I’m not worried about the nutrient levels, because I feel like in my experience I’m at a good spot, but adding 5 ppm of nitrate per month is a little faster than I’d like. I have done many reefs over the years but nothing close to 200 gallons. 200 gallons of water is a lot of water to change in order to bring it down and at 2 gallons a day I was already changing 14 gallons a week and it was still going up. I’m going to need to cut down on feeding.

So here’s the stupid question: as I said, I have no light on the aquarium. That changes in a couple of weeks. An aquarium with light should see more of a reduction in nitrate and phosphate than one without one because of photosynthesis, correct? :expressionless-face:

 

[areefer01]

In the open ocean and unpolluted reefs we typically see values like this:

https://www.sciencedirect.com/science/article/abs/pii/S0967064513000714
At sites near the barrier reef, nutrient concentrations are about DIN < 1 umol/L, DIP ~ 0.1 umol/L, values close to those in the open ocean.

Note that 0.1 umole/L phosphate= 10 ug/L = 0.01 ppm phosphate.

Obviously not on the same level as science direct and its respected article but here are my results from a recent dive trip in December, 2024. Beqa Island, Fiji.

This was for fun nothing more. ATI is used because that is 99% of my historical data and I had a spare test. Obviously science direct has better protocols than me collecting water during a safety stop over an Acropora reef in high current :)

https://lab.atiaquaristik.com/share/72b73abb2da6128f5f10

 

[Reefering1]

Obviously not on the same level as science direct and its respected article but here are my results from a recent dive trip in December, 2024. Beqa Island, Fiji.

This was for fun nothing more. ATI is used because that is 99% of my historical data and I had a spare test. Obviously science direct has better protocols than me collecting water during a safety stop over an Acropora reef in high current :)

https://lab.atiaquaristik.com/share/72b73abb2da6128f5f10

:thinking-face:

 

[Lasse]

Obviously not on the same level as science direct and its respected article but here are my results from a recent dive trip in December, 2024. Beqa Island, Fiji.

Thank you for that!!

Sincerely Lasse

 

[Randy Holmes-Farley Verified Community Expert]

Obviously not on the same level as science direct and its respected article but here are my results from a recent dive trip in December, 2024. Beqa Island, Fiji.

This was for fun nothing more. ATI is used because that is 99% of my historical data and I had a spare test. Obviously science direct has better protocols than me collecting water during a safety stop over an Acropora reef in high current :)

https://lab.atiaquaristik.com/share/72b73abb2da6128f5f10

Looks good to me. Also a good test of the accuracy for the major ions. Thanks.

 

[Randy Holmes-Farley Verified Community Expert]

So here’s the stupid question: as I said, I have no light on the aquarium. That changes in a couple of weeks. An aquarium with light should see more of a reduction in nitrate and phosphate than one without one because of photosynthesis, correct? :expressionless-face:

Very likely, yes.

 

[Timfish]

Love this write up and makes me think twice to throw GFO at my phosphate numbers. It seems I’ve reached a “for now” equilibrium of floating between 0.12ppm and 0.18ppm phosphate.
I’m not currently doing anything for phosphate removal besides weekly water changes. My tank and coral look great so I’ve been just letting them hover. I want so bad to put some GFO in a reactor and get back down to the under 0.1 range though. The number chaser in me just wants this. I also wonder if my growth would be more optimal. My primary goal is rapid Acropora growth. I’m getting decent growth, I’m just a little obsessed with wanting faster growth (need a real reason to start a new tank for frags :)) I have strong flow, high par, and stable electrolyte/buffer parameters using AFR and weekly 10pct water changes with TMPR. No ICP to know where I’m at with traces.
Should I continue to monitor or toss my GfO reactor back online for goal of lower phosphate considering the context. Thanks for all the information!

Ultimately I plan to start a refugium but I’m waiting on a sale to buy all the Neptune gear at once.

Updated FTS for reference

Nice system. :) Keep in mind faster growth isn't necessarily a good thing. Growth can also be variable not only between species/genotypes but year on year as well. Additionally, directly feeding can be problematic as there are species specific prefferences. I would encourage you to watch Delbeek's video on the problems at the Steinhart aquarium when they dropped thier PO4 numbers. Here's some links:

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0207956
https://www.sciencedirect.com/science/article/abs/pii/S0044848619310282
https://www.researchgate.net/public...ts_of_light_water_motion_and_artificial_foods
https://pmc.ncbi.nlm.nih.gov/articles/PMC3758286/
https://esajournals.onlinelibrary.wiley.com/doi/10.1002/ecy.1912

 

[Timfish]

I’m not understanding why you are showing an old post of mine that is basically no different than my article?

Corals can thrive at below 0.03 ppm phosphate, as they obviously do in the ocean because inorganic phosphate is not the only source of phosphate available. if those other sources are adequate, then the tank will thrive.

https://www.sciencedirect.com/science/article/abs/pii/S0048969722070449
In addition to their heterotrophic diet, corals have access to DIP and DOP mainly through their symbiotic dinoflagellates and associated microbes. While DIP occurs in nanomolar concentrations in reef waters (Bell et al., 2007; Morrison et al., 2013), DOP compounds can account for 70–90 % of the total dissolved phosphorus pool (Ruttenberg and Dyhrman, 2012).

Thank you for the article, I hadn't seen that one yet.

Research done by Southampton University has shown phosphate deficiency has serious repercusions on corals. They've identified a threshold level of .03 mg/l with corals in their system. . . .

Your wording "serious repercussions" seems to imply that corals fare poorly at lower levels, which clearly is not the case. Do you think that a slower growing coral is suffering "serious repercussion"?

How is dismissing my warning about about Rosset's finding PO4 levels below .03 mg/l can and your article advocating keeping PO4 levels above Rosset's .03/mg/l "basicly the same thing"? That strikes me a quite a disconnect.

Yes, you're quite right, if corals get enough POP and DOP they can do quite nicely without DIP. But if you've been confidant for a couple decades our our reefs systems have had enough POP and DOP to maintain healthy photobiology in coral even if DIP is below Southampton's threshold why are you changing your recommendations now? If you agree with Rosset. Wiedenmann and de Angelo's research showing aquarium corals can suffer po4 deficiency below .03 mg/l why did dismiss my warning that PO4 numbers can have serious reppercusions? Why it take so long for you to update your recommendation?

Over the last few years you've been adjusting your numbers up from below .03 to .02 mg/l PO4 to .02 - .1 mg/l PO4 to .03 - .1 mg/l to .06 - .3 mg/l. What was your reasoning? I can see .02 and .03 as those two quantities are in Rosset's paper and I can see .3 mg/l as that's what upwelling exposes corals to but what research were you using to determine .1 mg/l PO4 as an upper limit and where did you get .06 as a lower limit for PO4?

 

[areefer01]

Looks good to me. Also a good test of the accuracy for the major ions. Thanks.

Thanks. As I noted it was just for fun as I had a spare test. This was nothing scientific. I have a few more dive trips booked and I'll collect similar samples to the best of my ability. I may also try a Aquabiomics test. I reached out to them asking how to best collect that sample which is helpful. This one will require a bit more work on the boat so we will see.

Hope your day is well.

 

[Randy Holmes-Farley Verified Community Expert]

How is dismissing my warning about about Rosset's finding PO4 levels below .03 mg/l can and your article advocating keeping PO4 levels above Rosset's .03/mg/l "basicly the same thing"? That strikes me a quite a disconnect.

You said they showed serious repercussion of "phosphate deficiency". Your choice of words. No such deficiency or your implied serious repercussions of a deficiency are possible if my recommendation is above their level.

Corals can do fine below 0.03 ppm phosphate, as they do in the ocean.

I've said both of these things very clearly in this article and don't see a problem.

I also made it clear in this article that my recommended phosphate range is higher than it has been in the recent past, and it is much higher than in the distant past. That evolving change is based on a wide range of sorts of data that show that corals can thrive in many different environments. it does not mean that corals cannot thrive at levels above or below my recommendation given the right conditions.

 

[Miami Reef]

Bulk Reef Supply sent a newsletter of their new recommended tank parameters.

 

[Randy Holmes-Farley Verified Community Expert]

Bulk Reef Supply sent a newsletter of their new recommended tank parameters.

What fun would it be if we all agreed on everything? lol

 

[Hans-Werner]

Love this write up and makes me think twice to throw GFO at my phosphate numbers. It seems I’ve reached a “for now” equilibrium of floating between 0.12ppm and 0.18ppm phosphate.
I’m not currently doing anything for phosphate removal besides weekly water changes. My tank and coral look great so I’ve been just letting them hover. I want so bad to put some GFO in a reactor and get back down to the under 0.1 range though. The number chaser in me just wants this. I also wonder if my growth would be more optimal. My primary goal is rapid Acropora growth. I’m getting decent growth, I’m just a little obsessed with wanting faster growth (need a real reason to start a new tank for frags :)) I have strong flow, high par, and stable electrolyte/buffer parameters using AFR and weekly 10pct water changes with TMPR. No ICP to know where I’m at with traces.
Should I continue to monitor or toss my GfO reactor back online for goal of lower phosphate considering the context. Thanks for all the information!

Ultimately I plan to start a refugium but I’m waiting on a sale to buy all the Neptune gear at once.

Updated FTS for reference

I personally think you will not get faster growth with less phosphate, more likely the opposite, especially in Acropora.

At the moment I am running experiments with feeding fish which should specifically increase phosphate excretion and/or reduce N excretion in fish, and corals are responding very positively with everything, color, PE and growth despite phosphate concentrations already being very high.

@all, think about this approach: Ignore everything you "know" and just follow the directions the corals show you.

 

[skey44]

I personally think you will not get faster growth with less phosphate, more likely the opposite, especially in Acropora.

At the moment I am running experiments with feeding fish which should specifically increase phosphate excretion and/or reduce N excretion in fish and corals are responding very positively with everything, color, PE and growth despite phosphate concentrations already being very high.

@all, think about this approach: Ignore everything you "know" and just follow the directions the corals show you.

I briefly tried running the GFO and my phosphate was falling too fast and headed too low for my comfort. Currently back hanging out at 0.12 and growth, color, health all seem great still. I was trying to fix a nonexistent problem. No significant algal growth either. I’m going to let it hang out higher (0.12 seems like a happy medium) as there seems to be no trouble/slow growth as a result.

 

[CHSUB]

Just got my ICP test results this morning. Some might consider my nutrients low, I don’t. I’m getting the best growth, color, pe in all corals I have ever experienced. Zero nuisance algae and still need to clean the glass daily to keep it crystal clear. Imo, adding inorganic nutrients is only needed in very rare cases. I don’t believe “we” have figured out how to improve how Mother Nature does it.

 

[Hans-Werner]

Just got my ICP test results this morning. Some might consider my nutrients low, I don’t. I’m getting the best growth, color, pe in all corals I have ever experienced. Zero nuisance algae and still need to clean the glass daily to keep it crystal clear. Imo, adding inorganic nutrients is only needed in very rare cases. I don’t believe “we” have figured out how to improve how Mother Nature does it.

I think it can't be ascribed to one or two factors. It is a complex system and everything plays a role, lighting, trace elements, dissolved nutrients, biology, particulate nutrients etc..

LED seems a different quality in lighting compared to metal halides and fluorescent lamps wich I ascribe to the 450 nm peak.

Addition: Particulate nutrients also seem to have a special quality for corals since after feeding they show no net uptake of dissolved reactive phosphate from the water for some time.

 

[CHSUB]

I think it can't be ascribed to one or two factors. It is a complex system and everything plays a role, lighting, trace elements, dissolved nutrients, biology, particulate nutrients etc..

LED seems a different quality in lighting compared to metal halides and fluorescent lamps wich I ascribe to the 450 nm peak.

I agree. Many problems in reef aquariums are created before the first coral is added…

 

[Randy Holmes-Farley Verified Community Expert]

Imo, adding inorganic nutrients is only needed in very rare cases. I don’t believe “we” have figured out how to improve how Mother Nature does it.

I certainly don't doubt that coral can thrive at natural ocean levels of nutrients if other conditions are right, but I cannot see how one or more examples shows that the reverse is "rare". That also may not be how you arrived at the "rare" conclusion, but I've seen enough examples of it to say that, IMO, it is not rare.

 

[CHSUB]

I certainly don't doubt that coral can thrive at natural ocean levels of nutrients if other conditions are right, but I cannot see how one or more examples shows that the reverse is "rare". That also may not be how you arrived at the "rare" conclusion, but I've seen enough examples of it to say that, IMO, it is not rare.

I don’t believe hobby test kits provide the resolution required to determine if a nutrient deficiency exists. Imo, nutrient deficiency are not common in most aquariums, especially when hobby testing show some level of a nutrient. I experienced a po4 deficiency many years ago that involved pale corals, stn that seemed corrected with po4 dosing. When I think about it now, I’m less convinced po4 dosing solved the problem. I feed my corals directly(for the last 8 months) , so maybe others don’t and require higher nutrients levels than natural levels? I’m amazed how directly feeding corals has benefited: color, growth, pe is great. So, in my mind, I have solved something: fed fish, low nutrients, directly fed corals.

 

[Randy Holmes-Farley Verified Community Expert]

I don’t believe hobby test kits provide the resolution required to determine if a nutrient deficiency exists. Imo, nutrient deficiency are not common in most aquariums, especially when hobby testing show some level of a nutrient. I experienced a po4 deficiency many years ago that involved pale corals, stn that seemed corrected with po4 dosing. When I think about it now, I’m less convinced po4 dosing solved the problem. I feed my corals directly(for the last 8 months) , so maybe others don’t and require higher nutrients levels than natural levels? I’m amazed how directly feeding corals has benefited: color, growth, pe is great. So, in my mind, I have solved something: fed fish, low nutrients, directly fed corals.

I've come across more than one reefer who states the opposite of what you claim just today in this one subforum. It's apparently not rare to see visible benefits to N and P above zero on hobby test kits.

This was posted just 2 hours ago:

This is purely my own opinion on acro care but I would get that no3 above 5 as a starting point. Keep it there for a couple of weeks to see if your acros like that and start coloring up. I would bet they not only start coloring up but start to grow a bit quicker. I never let my nitrate get below 5. The SPS clearly show a negative reaction when it has.
https://www.reef2reef.com/threads/no3-staying-very-low-in-mature-tank.1098552/post-13337618