Why your aquarium needs nitrates (no3)?

[Randy Holmes-Farley Verified Community Expert]

This is really interesting. I wonder which algaes. I can see GHA creating this type of micro environment as it easily traps detritus and food and that always seems, to feed it vs say valonia and it's structure. I think blowing the algae clean helps to at maybe slow it down

Even suspended phytoplankton can do it. :)

https://pmc.ncbi.nlm.nih.gov/articles/PMC4548154/
Alkaline phosphatase (AP) is a key enzyme that enables marine phytoplankton to scavenge phosphorus (P) from dissolved organic phosphorus (DOP) when inorganic phosphate is scarce in the ocean.

 

[Dan_P]

I agree with Randys comments above and also the authors do that - se their comments in my last quote in this post. I have been working with this post for 6 hours and therefore Randy was faster

The article shows that the coral animal can survive and grow very well in nutrition concentration of around 0.75 mg/L NO3 and 0.285 mg/L of PO4 compared with the control that has what aquarists think is normal in the wild.

It is not dealing with higher values - but this does not mean that higher values give the same, better or worse growth - it just say that during this condition all tested corals growth better than control (0.043 and 0.012 mg/L NO3/PO4)



This quote is from the same article and they have not demonstrate that low inorganic nutrients can indeed limit algae while not affecting corals - however they state this in the discussion part of the article. You have the example in your own aquarium - you boasted that your sun corals were thriving and their growth rate is exactly what you get if you don't give your photosynthetic corals light and nutrition. I can even imagine that you get worse growth in your photosynthetic corals if you force them to be completely heterotrophic because the food they capture has to go to both the coral animal and the symbiont's survival and growth. IMO - If you only uses the two outer endpoints (heterotrophic or autotrophic growth only) in corals that have zooxanthellae. - you get the best growth in pure autotrophic conditions.

The article did not do an experiment with the combination of heterotrophic and autotrophic conditions in the lab- as it is in nature.

However - they did a study in the wild. The NO3 concentrations was up to over 1 mg/L and phosphate around the figures for the long time lab experiments ~0.28 mg/L PO4. Excuse the long quote with my bold. Main source
here



This means if you compare a mixed feeding in systems with low nutrient concentrations and mixed feedings in system with high nutrient concentration - this study indicates that growth is at least twice as great when the water contains elevated inorganic concentrations of nutrients in addition to particulate food in nature

Instead of cherry picking quotes that seems to fit into your agenda - try to read the whole article and especially this part

There you can read things like this - as usually - my bold



But here is a very interesting thing



I dug up this article - and I will comeback later on because there are findings in it that may rock the fundings of the necessary to feed your acropora - with one exception

Sincerely Lasse

Lasse,

Nice clarification that you provide. I feel it is another example from @Randy Holmes-Farley post on observations and conjectures, that you can trust most observations, in this case a quote from the article was correct, but you can and should be skeptical of inferences drawn from such an observation, in this case inferences were too narrow or incomplete leading to potential misinformation. This example also highlights why having experts around is important: to provide a fuller interpretation of complex stuff.

Dan

 

[Dan_P]

Even suspended phytoplankton can do it. :)

https://pmc.ncbi.nlm.nih.gov/articles/PMC4548154/
Alkaline phosphatase (AP) is a key enzyme that enables marine phytoplankton to scavenge phosphorus (P) from dissolved organic phosphorus (DOP) when inorganic phosphate is scarce in the ocean.

Can phosphate bound to calcium carbonate surfaces be harvest as well?

 

[Randy Holmes-Farley Verified Community Expert]

Can phosphate bound to calcium carbonate surfaces be harvest as well?

Phosphate that is bound to surfaces is in on/off equilibrium with the water. Nearby organisms can get it when it is off, but not when it is on the surface.

Enzymes cannot release it the way they would from an organic molecule that is covelently binding phosphate through a C-O-P bond.

 

[TokenReefer]

Phosphate that is bound to surfaces is in on/off equilibrium with the water. Nearby organisms can get it when it is off, but not when it is on the surface.

Enzymes cannot release it the way they would from an organic molecule that is covelently binding phosphate through a C-O-P bond.

When algae grows on phosphate bound surfaces is it just taking advantage of the released phosphate immediately at that boundary layer? Does increased flow move it away from that 'high availability' area in a meaningful way?

 

[Dan_P]

Phosphate that is bound to surfaces is in on/off equilibrium with the water. Nearby organisms can get it when it is off, but not when it is on the surface.

Enzymes cannot release it the way they would from an organic molecule that is covelently binding phosphate through a C-O-P bond.

I should have did a little more research before asking my question. There are bacteria known as phosphate solubilizing bacteria, so, my question should have been “have you heard or read anything that indicates that these organisms might be relevant in our aquaria”?

 

[CHSUB]

That is largely false.

Many marine algae contain externally anchored alkalinity phosphatase to break phosphate off of organic compounds and take it up. Thus, it may be impossible to limit marine microalgae by reducing phosphate without hurting corals.

Similarly, many marine algae can take up or use externally anchored enzymes to use various organic forms of nitrogen to survive in nutrient poor conditions, including amino acids, nucleic acids, and urea.

So if I’m understanding correctly: marine algae can use strategies to obtain p and n from organic sources. Cyanobacteria can fix atmospheric n2 and use it while also trapping organics for use. Bacteria can go dormant and has numerous strategies to survive when nutrients are low. All three: numerous species of marine algae, Cyanobacteria, and bacteria have strategies to thrive in inorganic nutrient poor conditions. Since many hobbyists rely on increasing inorganic nutrients to spur competition and growth of other organisms when battling dinoflagellate; what other organisms are the hobbyist relying on?

 

[CHSUB]

It is not dealing with higher values - but this does not mean that higher values give the same, better or worse growth - it just say that during this condition all tested corals growth better than control (0.043 and 0.012 mg/L NO3/PO4)

I agree and I’m not sure that a hobbyist that has 20 ppm no3, for example, can use this study to better manage their aquarium. Would this study no confirm that no3 at 0.75 ppm be adequate insurance?

This quote is from the same article and they have not demonstrate that low inorganic nutrients can indeed limit algae while not affecting corals

I agree but it demonstrates that corals have some amazing abilities by feeding multiple ways that other organisms don’t necessarily possess.

you boasted that your sun corals

Boasted, “excessively proud and self-satisfied talk about one's achievements, possessions, or abilities” I completely disagree with your assessment of my sun corals and its success. I find the term you selected, “boasted” to be insulting and not warranted. Regardless, i used it as an example that it is easy to satisfy the needs of corals without zooxanthella by providing prey foods. This, imo, confirms that while it’s impossible to supply the amount of available food in natural reefs; it is possible to supply an adequate amount for both photosynthetic and non-photosynthetic corals.

your photosynthetic corals if you force them to be completely heterotrophic

My nutrient range in my aquarium during its entire existence has been somewhere it the middle of both the control and the nutrient pulse levels. So imo I’m not forcing my corals to feed any way, only their preference.

Instead of cherry picking quotes that seems to fit into your agenda-try to read the whole article and especially this part

I read the article in its entirety closely, multiple times, and highlighted some items I found interesting. Here is a comment about the article I made, “I will agree this experiment gives evidence that corals can perform well only relying on zooxanthella”.

I disagree with your assessment and I don’t have an agenda. I supply pictures and success examples to show it works; not to insist it’s the only path to success but a path.

 

[Lasse]

The article is titled Elucidating an optimal diet for captive Acropora corals and I have it attached in this post. They did a test run with 7 different setup. 5 with extra particulate food and 1 control and one with raw unfiltered saltwater.

1. Control (CTL): Flow-through ultra-filtered seawater (0.04 μm) with no additives.

2. Unfiltered (RAW): Unfiltered seawater sourced from Cleveland Bay (lat.: 19°155.83′S, long.: 146°88.116′E) subjected to a hydro-cyclone filtration only.

3. Artificial (ATF): A LC-PUFA-rich, sodium alginate-bound formulated diet developed at AIMS. (3 g tank−1 WW). This diet contained a
mixture of intact and hydrolysed marine and terrestrial ingredients.J.A. Conlan, et al. Aquaculture 513 (2019) 734420
(Commercial in confidence formulation, details not provided). This diet was of the same formulation as those described in Conlan et al. (2018, 2017a). In the present study, this diet was provided continuously in an attempt to improve its efficacy.

4. LC-PUFA-rich diet (LONG): A LC-PUFA-rich, unbound, formulated
diet developed at AIMS. (3 g tank−1 WW)

5. LC-PUFA-deficient diet (SHORT): A formulated, unbound diet developed
at AIMS, containing comparatively low LC-PUFA levels. (3 g
tank−1 WW)

6. Phytoplankton (ALG): Isochrysis galbana cultured at AIMS using F2
culture media (1000 cells mL−1) (I. galbana was chosen due to its
naturally high levels of DHA (Olsen et al., 2000)).

7. Combination (COMB). Co-feeding of the ALG and LONG diets in
equal parts. (500 cells mL−1 and 1.5 g tank−1 WW, respectively).

1 and 2 (CTL and RAW) had this composition

The test was 90 days and the best results was achieved with feeding Isochrysis galbana but control and RAW was not far away from the results with living micro algae. It was only between 2 to 5 % lesser weight gain depending on species.

Its an interesting reading and it strengthen me in my believe that it many times is enough with what the aquarium is producing in organic particles if you do not filter them out for photosynthetic corals. Sun corals is another thing - they are not photosynthetic

Sincerely Lasse

 

[Tripod1404]

Phosphate that is bound to surfaces is in on/off equilibrium with the water. Nearby organisms can get it when it is off, but not when it is on the surface.

Enzymes cannot release it the way they would from an organic molecule that is covelently binding phosphate through a C-O-P bond.

Some bacteria can release covalently bound phosphate by secreting organic acids. If I remember correctly, sea grass species form symbiotic relationships with such bacteria.

 

[Randy Holmes-Farley Verified Community Expert]

Some bacteria can release covalently bound phosphate by secreting organic acids. If I remember correctly, sea grass species form symbiotic relationships with such bacteria.

Phosphate on calcium carbonate surfaces is ionically bound, not covalent. Is that what you mean? I agree that an organism that secreted acid will promote release, though that is a limited supply.

It may also be the case the organisms can release acid to break down certain especially weak covalent organic phosphates.

 

[Lasse]

Boasted, “excessively proud and self-satisfied talk about one's achievements, possessions, or abilities” I completely disagree with your assessment of my sun corals and its success.

Cambridge Dictionary also say it can stand for the following -

It can also refer to possessing or displaying something notable and impressive

and of cause that was what I meant - I´m sorry I read the whole article - as usually - and pick the meaning I meant. I am a non native English speaker and sometimes need to check that I use the right word. It was not my meaning to insult you.

Would this study no confirm that no3 at 0.75 ppm be adequate insurance

No its only says what happens at 0.75 mg/L NO3 It does not say that it will grow better or worser with higher concentrations. It can be that way as this below - but the actual article says neither here nor there. And there can be other reason than growth that make you to take the decision to run in higher NO3 concentrations

Although I have yet to see any peer reviewed studies that test nitrate levels higher than 5 ppm, I personally don’t think most corals really care much about the actual concentration once it is over 1 ppm. From a coral’s perspective, 50 ppm might not be that different from 5 ppm.

Nitrate, like other charged ions, cannot diffuse directly across the cell membrane, so it has to be taken up by transporter proteins or ion channels. The uptake of these ions generally follows Michaelis–Menten kinetics, where the uptake rate increases with concentration, but once the transporters are saturated, the uptake rate will not change much even if the concentration keeps rising. Unlike phosphate, which can bind to or react with many substrates, nitrate generally is not a very reactive ion on its own, so I do not really expect it to do much just floating around in the water.

Most of the research on nitrate uptake kinetics in corals seems to indicate that uptake rates generally saturate at levels below 1 ppm. Although I certainly cannot rule out the possibility that some species might saturate at higher concentrations, I do not see much reason to believe they would be drastically different from the species that have already been tested.

Here are two papers on this topic if you are interested:
Nitrate uptake by the reef coral Diploria strigosa: Effects of concentration, water flow, and irradiance
High phosphate uptake requirements of the scleractinian coral Stylophora pistillata

The last article is interesting.

Sincerely Lasse

 

[smitten with ocean life]

i was going to say the same thing. we need to keep in mind that those who are in other countries and who native tongue isn't English, might not be using the words we would use. or we might be interpreting it wrong. just something to keep in mind carry on!

 

[CHSUB]

. It was not my meaning to insult you.

Sorry! I guess I was being to sensitive, haha! Which I’m usually not and like a lively discussion.

Back to the discussion!

 

[TokenReefer]

I run on apples. I need an apple every so often to survive and some extra apples to grow. I don't need apples piled on me or around me for this but I do need them to be available to survive on and it'd be nice to have some extra to help me grow bigger (of course I'll need even more apples then). Having more apples now won't make me grow faster because I can only eat so much at a time but having none or few could slow me down. Having access to the apples is what's important to me. As I grow, eventually because of my additional size, my survival and any desired additional growth needs will require more apples than my earlier survival and growth apple requirements. This will keep scaling as I grow. I eat every bit of the apple. Very efficient at it. So much so that if you stopped by in between you might not even be able to see any evidence of apples and think I was starving but I'm not. Sometimes there's extra apples in the delivery and so you might see those lying around until I get to them.

Sorry alot of this is over my head so I have to dumb it down to try to understand..

 

[CHSUB]

Tested no3 today in my aquarium:

No3 @ 1.06 ppm Hanna LR and confirmed with Salifert @ 1.0 ppm.

June 2025, No3 @ 0.07 ppm Hanna LR. That represents a 1414% increase in 1 year.
Tank in June 2025:


Observations and conclusions:
Only visible evidence is growth of all inhabitants in the one year test period. In this aquarium no3 seems to play no role in the health or growth of a thriving system. No3 appears to be accumulating at a minimum level. Neither level during the studied period has any visible impact.

Today:


Thoughts ?
Original hypothesis: “no3 doesn’t matter”, is confirmed as nitrates are accumulating. At what level does no3 accumulation have a negative impact? Imo, multiple years as long as maintenance remains consistent.

 

[Dan_P]

Tested no3 today in my aquarium:

No3 @ 1.06 ppm Hanna LR and confirmed with Salifert @ 1.0 ppm.

June 2025, No3 @ 0.07 ppm Hanna LR. That represents a 1414% increase in 1 year.
Tank in June 2025:


Observations and conclusions:
Only visible evidence is growth of all inhabitants in the one year test period. In this aquarium no3 seems to play no role in the health or growth of a thriving system. No3 appears to be accumulating at a minimum level. Neither level during the studied period has any visible impact.

Today:

Thoughts ?
Original hypothesis: “no3 doesn’t matter”, is confirmed as nitrates are accumulating. At what level does no3 accumulation have a negative impact? Imo, multiple years as long as maintenance remains consistent.

Observation: visible coral growth.
Note: no before-after photographs. We have no idea how well coral are growing.

Observation: NO3 concentration now and one year ago.
Note: No knowledge of nitrate concentration between these two measurements.

Conclusion About The Importance Of Nitrate For Coral Growth: None
Note: Lackadaisical record keeping provides little support for the hypothesis that the presence of nitrate is unimportant. Moreover, uncontrolled experiments in the study of coral growth can be meaningless.

 

[CHSUB]

Observation: visible coral growth

~ 1 year front tank growth progress

Observation: NO3 concentration now and one year ago

Graph 1 year no3:

 

[TokenReefer]

https://reefbuilders.com/2023/08/24/study-reveals-how-corals-gain-n-and-p-in-darwins-paradox/This might explain undetectable level yet thriving animals

 

[CHSUB]

https://reefbuilders.com/2023/08/24/study-reveals-how-corals-gain-n-and-p-in-darwins-paradox/This might explain undetectable level yet thriving animals

Yes and thanks, however we have been discussing the study behind this article posted by lasse.