Why your aquarium needs nitrates (no3)?

[sixty_reefer]

Folks have often implicated degradation of organics in sand as a source of nutrients for overlying mats of algae/cyano/dinos/etc. it may sometimes be the case, but in at least some cases (dinos or cyano in a new tank on the sand) it’s hard to pit the finger on accumulated organics.

I can see the distinction you're making. In my opinion newer aquariums are a different story, they typically have less biological maturity, less competition and often fewer predators operating within the sand bed than more established aquariums, because of that I don't think significant organic accumulation is always necessary for a mat to form, a lack of competition alone may be enough to allow certain organisms to establish themselves.

This is largely why I've been using the phrase "it depends" throughout this thread, different situations may have different explanations, what drives mat formation in a new aquarium may not be the same thing that drives it in a more mature aquarium.

Have you ever had the opportunity to see a pure laboratory culture of dinoflagellates? I recently came across a photograph of a pure culture of Ostreopsis ovata and found it fascinating, what surprised me the most was how difficult photographs of pure cultures seem to be to come across and how difficult they must be to keep free from predators and competing organisms.

 

[CHSUB]

How do you know that first part?

I think there is plenty of empirical data that suggests otherwise.

The understanding that the vast majority of typical closed systems will never be nitrogen limited

I would first describe my definition of a typical system: a system with mechanical, chemical(ie. Carbon and/or GFO) and protein skimming filtration only; not using carbon dosing or any actively fed bacteria colonies. Daily fed fish, a large CUC, “live” rock and a moderate amount of corals is how I would describe a typical hobby reef aquarium. With that definition, I feel very confident from both observation and experience that the vast majority of these systems will never be nitrogen limited.

I have seen zero evidence to the contrary. What I have seen is hobby test kit results of a single nitrogen source(no3) and a conclusion that nitrogen is limited. Occasionally the hobbyist increases no3 to an arbitrary value and believes there is a visible difference. I would describe this as “hobby observation” and at best a coin flip result. Imo a better description of the above scenario is the added nitrates are insurance so the new, inexperienced hobbyist can cross a nitrogen deficiency off a list of potential problems.

 

[Tripod1404]

The understanding that the vast majority of typical closed systems will never be nitrogen limited

I would first describe my definition of a typical system: a system with mechanical, chemical(ie. Carbon and/or GFO) and protein skimming filtration only; not using carbon dosing or any actively fed bacteria colonies. Daily fed fish, a large CUC, “live” rock and a moderate amount of corals is how I would describe a typical hobby reef aquarium. With that definition, I feel very confident from both observation and experience that the vast majority of these systems will never be nitrogen limited.

I have seen zero evidence to the contrary. What I have seen is hobby test kit results of a single nitrogen source(no3) and a conclusion that nitrogen is limited. Occasionally the hobbyist increases no3 to an arbitrary value and believes there is a visible difference. I would describe this as “hobby observation” and at best a coin flip result. Imo a better description of the above scenario is the added nitrates are insurance so the new, inexperienced hobbyist can cross a nitrogen deficiency off a list of potential problems.

These are highly generalized assumptions. There is plenty of evidence, both scientific and anecdotal, that shows coral growth improves with detectable nitrate levels.

 

[Fishy888]

Wouldn't it be possible that what we're seeing is a shift from organisms relying primarily on inorganic nutrients in the water column to organisms exploiting organic nutrients concentrated within the mat itself?

In low inorganic nutrient situations, the mat seems to form directly over surfaces where detritus, dissolved organics and microbial activity are already concentrated, by creating a physical structure, the mat may establish its own microenvironment, allowing nutrients released from the sand bed, biofilms and trapped organic matter to be captured and recycled more efficiently than they would be in the surrounding water.

What's interesting is that a similar pattern seems to occur in high nutrient systems, the water column chemistry may be very different, yet the mats still often develop around areas where organic matter accumulates, that makes me wonder whether nitrate and phosphate are sometimes only part of the story.

If the organisms within the mat are responding primarily to the local conditions they create for themselves, then the chemistry inside the mat could be very different from the chemistry of the surrounding aquarium.

If that's true, can we really identify the cause of the bloom simply by measuring residual nitrate and phosphate in the water column or are we missing the nutrient dynamics occurring within the mat itself?

I think that while there are some forms of bacteria, dinoflagellates, protists etc that rely heavily on ammonia/ammonium and nitrates, most of the pest “algae” we see in our systems do indeed rely on pockets of accumulated waste. Definitely cyano and dinos at the very least.

Most likely though, since our systems are not the ocean, as much as we would like them to be, we should keep a small amount of nitrates until we know for sure that not having them at all would work in our systems long term.

 

[Fishy888]

I believe I may have unintentionally deviated the thread a little, sorry @CHSUB

I suspect the organics may be concentrated in the sand bed beneath the mat, the mat itself could be able to affect the nutrient exchange between the sand bed and the water column creating a local micro environment that in part could separates the sand from the water column. The air bubbles we often see trapped within the mat could be a clue that not much is escaping to the water column.

IMO, it may simply be an effective feeding strategy as inorganic nutrients in the water column become depleted or when excess organic matter becomes trapped within the sand bed.

This is my thinking also. Plus, while air gets trapped in the mats, there is some circulation of water, hence waste, that circulates under the sand bed. It also falls on top of the mats too. Fish poop, uneaten food, blowing debris off the rocks etc.

 

[Fishy888]

Why would organics be concentrated in the mat if organisms in the mat are consuming them?

My thoughts are that they form over the organics and over time other organic compounds such as fish poop etc get deposited over them, kind of like throwing gasoline on a fire.

For me this begs the question, at what rate are the organics consumed by the mats and their constituents? Knowing that would help here. I see I need to look into this more.

 

[Dan_P]

Nope, I have 3 measurements included in my ICP that measure organics; but yes not to common: SAK254, NPOC, TNb.

Nice!

Unfortunately, these water measurements (I measure them too in experimental systems mostly) are about as useful as sniffing the tailpipe of a car to figure out why it’s running poorly, but I continue to look for a signal like the SETI people. They have minimal diagnostic use when trying to understand benthic organism growth. Benthic life could be getting must of its food locally and not much from the water. Hard to know for sure. Lass and others have thought about the notion that there could be a concentrated flux of life supporting stuff flowing from the substrate ranging from PO4 to organic chemicals like amino acids. It’s an attractive model but difficult as hell to test. As for understanding planktonic organism growth with these C and N measurements, they are probably too coarse (I still collect them). Having C and N concentrations are almost of no value without some notion of what chemical compounds are present. By the way your C and N numbers are at the low end compared to other R2R aquaria (see total nitrogen vs total organic carbon and the TOC survey plots below). Moreover, if you were to observe oxygen consumption over time for a water sample from your system, you would likely see little or no oxygen consumption, suggesting that the material containing the C and N do not support heterotrophic life very well. Very frustrating.

There is a water sample that might be more useful to analyze: pore water. I still think and hope there is a diagnostic future for pore water analysis. There are inexpensive methods for sucking out the water between the sand grains without drawing in the overlaying water. You’ll find ammonia and phosphate, and oxygen and pH values that might be really whacko. And these values will differ from place to place. Might be fun sampling this water directly under a cyanobacteria mat to test the flux model.

 

[Fishy888]

The understanding that the vast majority of typical closed systems will never be nitrogen limited

I would first describe my definition of a typical system: a system with mechanical, chemical(ie. Carbon and/or GFO) and protein skimming filtration only; not using carbon dosing or any actively fed bacteria colonies. Daily fed fish, a large CUC, “live” rock and a moderate amount of corals is how I would describe a typical hobby reef aquarium. With that definition, I feel very confident from both observation and experience that the vast majority of these systems will never be nitrogen limited.

I have seen zero evidence to the contrary. What I have seen is hobby test kit results of a single nitrogen source(no3) and a conclusion that nitrogen is limited. Occasionally the hobbyist increases no3 to an arbitrary value and believes there is a visible difference. I would describe this as “hobby observation” and at best a coin flip result. Imo a better description of the above scenario is the added nitrates are insurance so the new, inexperienced hobbyist can cross a nitrogen deficiency off a list of potential problems.

Considering that even Hanna checkers can’t measure very low concentrations of most chemicals, I have to agree with you.

 

[CHSUB]

These are highly generalized assumptions. There is plenty of evidence, both scientific and anecdotal, that shows coral growth improves with detectable nitrate levels.

I will agree with anecdotal evidence…however what is “coral growth improves”; is that density or length or volume or strength? What metric is used to measure the improvement? I’m aware of one study that showed greater length with increased nitrates at specific amounts, however the density of the coral was less so the result was a fragile coral. The author suggested this was a negative affect in the wild. I have the same question with “detectable nitrate levels”. I have a detectable level of 0.25 ppm no3 with Hanna LR, however Salifert reads undetectable. “Detectable” has no scientific meaning as it depends on the test kit used, so anything that uses detectable as a metric would be completely anecdotal.

 

[Randy Holmes-Farley]

My thoughts are that they form over the organics and over time other organic compounds such as fish poop etc get deposited over them, kind of like throwing gasoline on a fire.

I don't disagree with that. They act as traps for stuff.

 

[CHSUB]

Considering that even Hanna checkers can’t measure very low concentrations of most chemicals, I have to agree with you.

I believe you are referring to the Hanna HR no3 checker and agree completely. However, the Hanna LR gives excellent low level detection.

 

[Fishy888]

I believe you are referring to the Hanna HR no3 checker and agree completely. However, the Hanna LR gives excellent low level detection.

Hanna is definitely the best with low level detection outside of a well funded laboratory.

I might pick a used LR at some point.

 

[Tripod1404]

I will agree with anecdotal evidence…however what is “coral growth improves”; is that density or length or volume or strength? What metric is used to measure the improvement? I’m aware of one study that showed greater length with increased nitrates at specific amounts, however the density of the coral was less so the result was a fragile coral. The author suggested this was a negative affect in the wild. I have the same question with “detectable nitrate levels”. I have a detectable level of 0.25 ppm no3 with Hanna LR, however Salifert reads undetectable. “Detectable” has no scientific meaning as it depends on the test kit used, so anything that uses detectable as a metric would be completely anecdotal.

There are studies that showed weight based improvement as well. Like the first image below shows growth rate at two different temperatures (normal at 26C and stressed at 29C) for intact or wounded corals. Second image shows wound healing (this is more for soft tissue growth). In both cases, control corals were grown in filtered sea water, or in filtered sea water supplemented with ammonia or nitrate.

I think what is especially striking about this research is it demonstrates that presence of an excess nitrogen source makes corals more resilient. It completely reverses suppression of wound healing rates under heat stress.

I find this research in agreement with a lot of hobby based anecdotal evidence, such as the overall fragility of corals in ULN systems, susceptibility to tip burning, etc.

Different nitrogen sources speed recovery from corallivory and uniquely alter the microbiome of a reef-building coral - PMC

Corals are in decline worldwide due to local anthropogenic stressors, such as nutrient loading, and global stressors, such as ocean warming. Anthropogenic nutrient loading, which is often rich in nitrate, inhibits coral growth and worsens corals’ ...

pmc.ncbi.nlm.nih.gov

About detectable nitrate levels, what I mean is if any kit can read any level of nitrate, it indicates that the tank has detectable levels of nitrate. This obviously doesn't mean if a kit reads zero or undetectable, nitrate is completely absent, as hobby level kits have relatively high "lower limit of detection". But if one gets a zero/undetectable reading, dosing a little nitrate (or raising it some other way) ensures it is not zero or too low. In other words, a zero/undetectable reading can truly be zero or too low, but dosing a little and bringing it to 1-2 PPM ensures it is not zero. In my opinion this is cheap insurance since very low nitrate can make corals more fragile and susceptible to stress, while even nitrate levels as high as 5-10 PPM has almost no drawback. It may even give slightly better growth.

 

[Fishy888]

There are studies that showed weight based improvement as well. Like the first image below shows growth rate at two different temperatures (normal at 26C and stressed at 29C) for intact or wounded corals. Second image shows wound healing (this is more for soft tissue growth). In both cases, control corals were grown in filtered sea water, or in filtered sea water supplemented with ammonia or nitrate.

I think what is especially striking about this research is it demonstrates that presence of an excess nitrogen source makes corals more resilient. It completely reverses suppression of wound healing rates under heat stress.

I find this research in agreement with a lot of hobby based anecdotal evidence, such as the overall fragility of corals in ULN systems, susceptibility to tip burning, etc.

Different nitrogen sources speed recovery from corallivory and uniquely alter the microbiome of a reef-building coral - PMC

Corals are in decline worldwide due to local anthropogenic stressors, such as nutrient loading, and global stressors, such as ocean warming. Anthropogenic nutrient loading, which is often rich in nitrate, inhibits coral growth and worsens corals’ ...

pmc.ncbi.nlm.nih.gov

About detectable nitrate levels, what I mean is if any kit can read any level of nitrate, it indicates that the tank has detectable levels of nitrate. This obviously doesn't mean if a kit reads zero or undetectable, nitrate is completely absent, as hobby level kits have relatively high "lower limit of detection". But if one gets a zero/undetectable reading, dosing a little nitrate (or raising it some other way) ensures it is not zero or too low. In other words, a zero/undetectable reading can truly be zero or too low, but dosing a little and bringing it to 1-2 PPM ensures it is not zero. In my opinion this is cheap insurance since very low nitrate can make corals more fragile and susceptible to stress, while even nitrate levels as high as 5-10 PPM has almost no drawback. It may even give slightly better growth.

I remember when everyone went for zero nitrates and zero phosphates. That didn’t work out too well. Then again everyone was practically starving their fish. In so doing they starved their corals too.

Admittedly, it would make me a little nervous to let nitrates get below 1 ppm.

 

[CHSUB]

There are studies that showed weight based improvement as well. Like the first image below shows growth rate at two different temperatures (normal at 26C and stressed at 29C) for intact or wounded corals. Second image shows wound healing (this is more for soft tissue growth). In both cases, control corals were grown in filtered sea water, or in filtered sea water supplemented with ammonia or nitrate.

I think what is especially striking about this research is it demonstrates that presence of an excess nitrogen source makes corals more resilient. It completely reverses suppression of wound healing rates under heat stress.

I find this research in agreement with a lot of hobby based anecdotal evidence, such as the overall fragility of corals in ULN systems, susceptibility to tip burning, etc.

Different nitrogen sources speed recovery from corallivory and uniquely alter the microbiome of a reef-building coral - PMC

Corals are in decline worldwide due to local anthropogenic stressors, such as nutrient loading, and global stressors, such as ocean warming. Anthropogenic nutrient loading, which is often rich in nitrate, inhibits coral growth and worsens corals’ ...

pmc.ncbi.nlm.nih.gov

About detectable nitrate levels, what I mean is if any kit can read any level of nitrate, it indicates that the tank has detectable levels of nitrate. This obviously doesn't mean if a kit reads zero or undetectable, nitrate is completely absent, as hobby level kits have relatively high "lower limit of detection". But if one gets a zero/undetectable reading, dosing a little nitrate (or raising it some other way) ensures it is not zero or too low. In other words, a zero/undetectable reading can truly be zero or too low, but dosing a little and bringing it to 1-2 PPM ensures it is not zero. In my opinion this is cheap insurance since very low nitrate can make corals more fragile and susceptible to stress, while even nitrate levels as high as 5-10 PPM has almost no drawback. It may even give slightly better growth.

Your article directly supports my hypothesis:

“Anthropogenic-derived sources of N, often in the form of nitrate, have deleterious consequences on coral growth and physiology (D’Angelo & Wiedenmann, 2014; Shantz & Burkepile, 2014) and can make corals more susceptible to seawater warming”

“Alternatively, natural sources of N (e.g., ammonium from fish excretion) can benefit corals by increasing coral growth and calcification (Holbrook et al., 2008; Meyer & Schultz, 1985; Meyer, Schultz & Helfman, 1984; Shantz & Burkepile, 2014). In fact, corals under ammonium enrichment receive more translocated carbon from Symbiodiniaceae (formerly Symbiodinium; LaJeunesse et al., 2018) than corals enriched with nitrate (Ezzat et al., 2015)”

“Indeed, anthropogenic- vs. naturally occurring N seem to have contrasting impacts on coral physiology and susceptibility to seawater warming (Burkepile et al., 2019)”


These 3 quotes compare Anthropogenic-derived(human added) sources of nitrogen(nitrates) vs natural sources(fish excretion) from ammonium. The conclusion is adding nitrates has a deleterious effect on corals and nitrogen from fish protects against heat stress, increases coral growth and calcification.

Here they explain why there is some possible reason that one example shows the same healing capacity despite the nitrogen source. There study had a lower amount of added nitrate.

In contrast, Renegar, Blackwelder & Moulding (2008) found that nitrate enrichment (~10 µM) reduced wound healing between ~10–60% depending on the coral species. The disparity in our findings can likely be explained by the lower nitrate concentrations used in our study (~4 µM), which are more environmentally relevant and thus less deleterious to corals.

 

[CHSUB]

About detectable nitrate levels, what I mean is if any kit can read any level of nitrate, it indicates that the tank has detectable levels of nitrate. This obviously doesn't mean if a kit reads zero or undetectable, nitrate is completely absent, as hobby level kits have relatively high "lower limit of detection". But if one gets a zero/undetectable reading, dosing a little nitrate (or raising it some other way) ensures it is not zero or too low. In other words, a zero/undetectable reading can truly be zero or too low, but dosing a little and bringing it to 1-2 PPM ensures it is not zero. In my opinion this is cheap insurance since very low nitrate can make corals more fragile and susceptible to stress, while even nitrate levels as high as 5-10 PPM has almost no drawback. It may even give slightly better growth.

I can agree a little, maybe.

 

[Reef Wizard Steven]

No3 @ 0.3 ICP and 0.26 Hanna LR…they have been lower, but tread is higher.
My aquarium is not the exception, it should be the rule….very clean, low inorganic nutrients, and well fed.

My nitrates in all of my tanks are under 10, and they are all doing okay. One of my tanks read .01 yesterday, but no issues with cyano or dinos. I agree, feeding a good variety of foods to your tank, and particulate foods to your corals, gives them a lot of what they need. I dose a little nitrogen into the tank when it reads 0, but all i really care about is it coming up on my checker. If I have anything at all on the checker, I'm happy. hahaha

 

[Dan_P]

“Detectable” has no scientific meaning as it depends on the test kit used, so anything that uses detectable as a metric would be completely anecdotal.

Not quite correct.

Detectable is an accepted term but needs context, like the limit of detection of the kit. For a Hanna Checker this is not reported but the uncertainty in the results is known. We cannot make strong claims about the actual concentration at values less than the reported confidence interval. As for Salifert, given the reliance of human sight to judge color intensity, the lower detection limit is highly variable and likely higher than the Hanna test.

Anecdotal is hearsay or not verified. The skeptic would regard most of this thread as hearsay and conjecture, but not without value. Observations and conclusions based on hobby aquaria are of less value compared to those from controlled studies. The premise of this thread is based on anecdotal data and conjecture, not controlled experiments. The information has value but making strong claims based on this type of information is probably not warranted, but a starting point for further study and discussion.

 

[Lasse]

There is a water sample that might be more useful to analyze: pore water. I still think and hope there is a diagnostic future for pore water analysis. There are inexpensive methods for sucking out the water between the sand grains without drawing in the overlaying water.

In a way - it has already been done - se below - the study continue in several pages

Today - I did a couple of analyses of my water below my DSB.

There has been a lot of discussions lately if there can be any total ammonia "pockets" in an existing mature tank. My tank is constructed in a way that it is rather easy to investigate this. It has a DSB in the refugium that have a reversed flow. I pump water down to the plenum and further up through the DSB

The flow is around 1000 L/H through this compartment of my aquarium with water containing around 0.1 NH3/NH4 as I show below (from march).

My PO4 is rather high and on its rising - for the moment 0.89 in the display water. 1 week ago - I had to switch my pump that supplies the plenum with water from the display. The same type but it seems to give what is supposed to do (around 120 L/H) -> 2880 L/24 hour. The old gave maybe only half that amount as it was old and tired. I have gone down with flow now to around 58 L/H.

What did I find and am I surprised? I´m not surprised by myself - it was in line with what I had expected due to experiences in both anaerobic and aerobic environments I have been working with before but it maybe will surprise some others - like those that always claim that tanks with a lot of corals and surface never can produce high amounts of NH3/NH4 and therefore all measurements that shows the opposite is false.

In clear figures

NH3/NH4 (total ammonia) in the DT - around 0.07 mg/L
NH3/NH4 (total ammonia) in the bottom of the DSB - around 0.89
PO4 in DT - around 0.89 mg/L
PO4 in the bottom of the DSB - around 1.78 (read 0.89 too but it was diluted fifty/fifty with new fresh saltwater)
NO3 in the DT - around 6.4
NO3 in the bottom of the DSB - around 3,8 mg/L
NO2 in the DT - around 0.013 mg/L
NO2 in the bottom of the DSB - around 0.03

These figures shows that activity of heterotrophic bacteria produce a lot of both NH3/NH4 and PO4 when they are feeded with organic carbon. It also shows that for the moment - my DSB mostly act as a NO3 producer (its probably mostly aerobic) and I have slowing down the flow and increase the organic carbon dosing in order to favour denitrification. The nitrification will happens at other places in my tank.

Sincerely Lasse

Sincerely Lasse

 

[CHSUB]

Not quite correct.

Detectable is an accepted term but needs context, like the limit of detection of the kit. For a Hanna Checker this is not reported but the uncertainty in the results is known. We cannot make strong claims about the actual concentration at values less than the reported confidence interval. As for Salifert, given the reliance of human sight to judge color intensity, the lower detection limit is highly variable and likely higher than the Hanna test.

Anecdotal is hearsay or not verified. The skeptic would regard most of this thread as hearsay and conjecture, but not without value. Observations and conclusions based on hobby aquaria are of less value compared to those from controlled studies. The premise of this thread is based on anecdotal data and conjecture, not controlled experiments. The information has value but making strong claims based on this type of information is probably not warranted, but a starting point for further study and discussion.

I would agree my entire conclusion is based on hobby aquaria and anecdotal observations. However the counter argument, measurable no3, is also anecdotal evidence and directly contradicts all scientific evidence.
This quote from the article above is only one example:
In contrast, Renegar, Blackwelder & Moulding (2008) found that nitrate enrichment (~10 µM) reduced wound healing between ~10–60% depending on the coral species. The disparity in our findings can likely be explained by the lower nitrate concentrations used in our study (~4 µM), which are more environmentally relevant and thus less deleterious to corals.

The study discussed wound healing of Pocillopora meandrina with nitrate addition. At ~10 µM enrichment vs ~4 µM the study found that the lower value increases healing and the higher reduced healing between ~ 10 to 60%. The authors further explain that the lower value is more environmentally relevant. Both test enrichment levels of nitrate are below or nearly below detection on a Salifert hobby test kit at 4 μM = 0.2484 ppm and 10 μM = 0.6210 ppm. Generally speaking the hobbyist when compared to controlled science studies of aquariums and nutrient levels for anything from algae control, coral growth, or limiting factors are not even in the same “universe”.