I agree especially in large tanks where manual removal could be a laborious task. My current tank is open top and TWV of 40 gallons, manual removal is quite easy.
Absolutely love this. When I first started reefing it was always low nutrients. I failed the first round because I unknowingly kept cycling my tank with too many water changes. When things were going good with mid range nutrients I would use gfos to bring nutrients back down and kill corals again and again. 0 nutrients why all the algae’s?!? After many years I’m very successful and I make sure to keep nitrates around 10 and phos.1-.2.Thoughts on Nutrient Target Ranges by Randy Holmes-Farley
Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want high targets, some want a particular ratio, and others just want to know what the heck is going on. Then comes the actions, with many people wanting to raise N and P and many wanting to lower them, and to do either one, aquarists need to wade through a wide range of possible actions. There are great tanks with very low nutrient levels, and there are great tanks with very high nutrient levels. We should not necessarily assume, however, that the same tank would work as well at both extremes of the ranges.
I do not have any magic recipe, or target ranges. While I will give some suggested target values at the end this article, I mostly want to address why so many aquarists have so many different ideas of what is best in their system. In other words, is it rooted in the science of nutrient uptake by corals?
Figure 1. A very high nutrient system maintained by Richard Ross, with nitrate sometimes above 100 ppm and phosphate above 1 ppm. Details in this link:
Rich Ross - Home Tank - guess the phosphate
This tank was built before r2r, here is a link to some links about the build. http://packedhead.net/home-reef/ Current test results: 03-17-2017 Ammonia (NH3-4) Good 0 0.000 - 0.050 mg/L 03-17-2017 Nitrite (NO2) Good 0.006 0.000 - 0.100 mg/L 03-17-2017 Phosphate...www.reef2reef.com
As we get into reasons why aquarists may have different opinions on what works best in their systems, let’s skip over those opinions that come just from reading somewhere what is best. They may be right or wrong, but it’s not so interesting to try to dissect them. Let’s instead focus on real reasons why a given reefer might correctly have an idea what is best in his or her system, and why that correct opinion may differ greatly from that of another aquarist. This information may help reefers focus in on what is best in their system, independent of what anyone else recommends.
1. A first, and very obvious, reason why reefers may have a dispute on what levels are best may be because they keep creatures with different abilities to extract what they need from the same levels of nitrate and phosphate. It is often stated that “soft corals prefer higher nutrient levels”, but how could that be and why would that be true?
First, is it true that different corals prefer different nutrient levels? The simplistic answer appears to be yes, different species have different abilities to collect nutrients (both in a lab and in the field), although comparative data is very sparse. In the natural environment, the distribution of, for example, soft corals vs acropora sometimes appears to relate to nutrient levels. This linked article shows that in some islands in Indonesia, that the preponderance of soft corals is higher in areas of higher nitrate while acropora dominates in higher phosphate locations. Of course there are other factors, and fingering one alone is impossible. Nevertheless, of the factors examined, nutrients appear to be among the best predictors of coral types at the different locations studied.
https://aquapublisher.com/index.php/ijms/article/html/1476
While this acropora vs soft coral differentiation is strong enough to identify in the wild, getting down the species level in terms of wild abundance at different nutrient locations has not been carefully evaluated. Nevertheless, there’s no reason to assume that corals do not vary significantly in their preferences for different nutrient environments for the reasons discussed in the next few sections.
Both nitrate and phosphate are taken up by corals and other organisms using active transporters on their surfaces exposed to the tank water. These transporters are proteins that span some sort of membrane between the coral body interior and the external environment. They bind phosphate or nitrate on the outside, and dump it inside. All organisms have these, from bacteria to people. Organisms control their uptake by adjusting the numbers and types of these transporters, and such effects have clearly been demonstrated in corals. This linked article, for example, shows such control in uptake capacity in the hard coral Stylophora pistillata.
High phosphate uptake requirements of the scleractinian coral Stylophora pistillata
SUMMARYSeveral untested aspects of the regulation of inorganic nutrient uptake were examined using nutrient depletion experiments with the symbiotic coral Stylophora pistillata. The total inhibition of phosphate uptake in artificial seawater lacking sodium indicates the involvement of a...journals.biologists.com
Indeed, corals that were fed 1 and 3 days before the uptake experiment took up phosphate 42 and 19% slower, respectively, than corals that were fed 21 days before.
…the saturated uptake rate of ammonium increased by 2.5-fold in the presence of 3.0 μmol l–1 of phosphate, thus indicating that the corals or their symbionts were lacking intracellular phosphate to take advantage of the inorganic nitrogen compounds dissolved in their surrounding medium.
There are many such transport proteins, and both the identity and the number of them determine how effectively one organism can take up what it needs relative to another. The upshot is that at, say 0.01 ppm phosphate, one organism may get all it wants while another cannot keep up with its need for phosphate. That is because of the nature and numbers of its uptake transporters in relation to its total need for the transported ion.
The article linked below gives a sense of the complexity and control for phosphate in a single well-studied bacterial system. That level of detailed information is lacking for typical corals we keep.
Molecular Mechanisms of Phosphate Sensing, Transport and Signalling in Streptomyces and Related Actinobacteria
Phosphorous, in the form of phosphate, is a key element in the nutrition of all living beings. In nature, it is present in the form of phosphate salts, organophosphates, and phosphonates. Bacteria transport inorganic phosphate by the high affinity phosphate transport system PstSCAB, and the low...www.mdpi.com
Nevertheless, there is information on phosphate transport and control mechanisms in corals, such as this article on Stylophora pistillata:
from it:
Our results showed the presence of active phosphate carriers both in the animal and the algal fractions…
Transporters in the animal and the algae presented different affinities for phosphate,…
The velocity of phosphate absorption increased in the light,…
A correlation was found between phosphate uptake rates and the organic or inorganic feeding history of the corals; rates were indeed 4.6 times higher in 8-week starved than in fed corals, and also depended on the repletion status of phosphorus stocks within the symbionts…
The fact that the uptake changed with feeding history means the corals must have changed either the number, or the type, or both, of its phosphate transporters. This result also hints at why it can be very undesirable to lower phosphate too quickly: corals may suffer while they try to ramp up their capability to get what they need from the new, lower level. Likewise with raising nutrients (which seems more of an issue with raising alkalinity too fast, but it’s the same story): corals cannot downregulate their uptake fast enough, and may take inside more of something than is good for them (like a starving person at an all you can eat buffet).
The article linked below even more clearly shows how complicated nutrient uptake can be in corals, with one dinoflagellate symbiont type originally identified from a Montipora verruciosa coral shown to have MANY transporters that it can use, and those may be different than the transporters other corals can use:
https://www.sciencedirect.com/science/article/abs/pii/S0048969720354358
from it:
In addition, this species possesses highly duplicated nutrient transporters including 13 phosphate transporter genes, 62 NO3− transporter genes, and 84 NH4+ transporter genes, which are higher than in other algal species.
Figure 2. A low nitrate system by Reef2Reef member Tusi. When the article was written, he noted phosphate of 0.05 ppm and nitrate of 0.5 ppm. This member may increase bioavailable bacterial foods, which may partly supply some of the N that corals need, by dosing bacteria and carbon dosing.
REEF OF THE MONTH - July 2021: TUSI's Amazing SPS Reef Revisited!
R2R Username: @TUSI Build Thread: Tusi's tank thread Editor's Note: This is the first time in the history of our Reef of the Month that we have revisited a tank that we previously featured. However, we think you will all agree that Tusi's reef is a tank that is highly deserving of this...
2. In addition to different organisms being used by different aquarists to assess what is best in nutrient terms, there are many different endpoints that one reefer may focus on that are different from another reefer, even assessing the same coral and its local environment. Some of these are:
Each of these has its own world of complexity associated with it. Just picking one at random, polyp expansion, we can easily see how one particular aquarist’s assessment of one particular coral may differ from another aquarist with the same coral if there are differences in lighting, flow, fish picking, other chemicals, pH, etc., that all themselves impact polyp expansion. Even if phosphate or nitrate has an effect on polyp expansion, it may be lost as noise under bigger effects of any of these other factors.
- Polyp expansion
- Growth rate
- Color
- Pest algae
- Pest dinoflagellates
- Pest cyanobacteria
- Pest diatoms
- Others
The same sort of variability is true for all of these other endpoints. As another example, the need for available nutrients to prevent dinoflagellate pests in new tanks with bare surfaces may be very different than a mature reef tank with no exposed surfaces where dinoflagellates might take hold. If one way to prevent dino pests is through competition with less troubling organisms occupying the same surfaces, say, bacteria or diatoms or green algae, then that system may benefit from higher nutrients to promote that competition, while other systems without exposed surfaces or with a more mature microbiome may not need those same nutrient levels to avoid dino pests.
3. Another factor that may vary between aquaria is how much N and P a given coral actually needs to grow in a given system. Accepting that factors such as lighting, pH, alkalinity, flow, and trace elements can potentially impact coral growth rates, the rate at which those same corals need to take up N and P will vary with those conditions. Faster growth means it needs more N and P to build new tissues. More need for N and P may mean a different optimal level of nitrate and phosphate in the water to be able to get what it needs. Thus, when one aquarist says 0.03 ppm phosphate gives the best growth, and a second one says no, she sees better growth of the same coral at 0.2 ppm phosphate, the difference could lie in any or all of these and other factors being different between the two systems.
4. Phosphate is known to have a direct and negative impact on hard coral skeleton growth. This linked article, for example, states
… our findings showed that inhibition of coral skeleton formation was due to absorption of phosphate on the skeleton, which inorganically inhibited normal development of juvenile coral skeleton.
https://link.springer.com/article/10.1007/s10126-019-09880-3
The implication of phosphate inhibition of skeletal formation has several implications:
5. Nutrient levels can impact reef tank microorganisms, including coral pathogens, in many different ways. Those microbiome changes may also impact indirect factors relating to corals, such as trace element availability (by microorganism uptake and thus less remaining for corals), and the feeding of corals on those microorganisms.
- Aquarists talking about optimal levels for a hard coral vs soft coral tank may come to different conclusions for this reason alone (perhaps among many others).
- Aquarists talking about only hard corals may be concerned primarily with growth (perhaps implicating elevated phosphate as bad) while others also referring only to hard corals may be concerned with other endpoints, such as color or polyp extension (which may not have the same implications for elevated phosphate)
As an example, this linked article discusses the microbiome effect of nutrients in the context coastal runoff, and suggests that phosphate is a bigger factor than nitrate with respect to one particular coral pathogen expanding in numbers.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8902694/
There are several implications of this microbiome effect of nutrients to the topic at hand.
6. Finally, and very importantly, nitrate and phosphate are far from the only sources of N and P in a reef tank. They may not even be the most used sources. Other sources of N include ammonia (preferred by most corals studied over nitrate), urea (an organic excreted by fish), amino acids, other soluble organics, and particulates including detritus and whole phytoplankton, zooplankton, bacteria and other organisms. Likewise, there are many forms of phosphate available, mostly including dissolved and particulate organics and microorganisms. In fact, the reduced availability of particulate foods in reef tanks is a likely reason that early efforts to mimic ocean levels of nitrate and phosphate in reef tanks led to poor outcomes. We just were not allowing enough N and P availability.
- The effects of nutrient levels on coral health may vary tank to tank based on what microorganisms are naturally present.
- Some of these effects (such as trace element bioavailability) may be “corrected” by dosing needed trace elements or sufficient particulate feeding (such as phytoplankton).
The implications that aquarists need to be critically aware of are:
How to Use This Info
- Nitrate level is a poor indicator of total N bioavailability.
- Phosphate may also not be a good indicator of total P availability
- Claims that, say, 0.5 ppm nitrate is plenty may not extrapolate to any aquarium other than the original one observed for reasons in 1. Same for phosphate.
- Likewise, claims that 10 ppm nitrate is much better than 2 ppm are also difficult to generalize across aquaria for these reasons.
- In general, having a few ppm nitrate may not be needed, or used by corals at all in some systems, but it is insurance that there is sufficient N.
I could drone on and on about these topics, and the discussion would get more and more detached from ordinary reefers experiences, so let’s focus on how one might use the info laid out so far, by looking at some very specific situations.
1. Limiting algae growth by limiting nutrients certainly works, but unless done in special circumstances, it usually risks coral problems from them not getting enough nutrients, or dino problems from them thriving at lower levels than other competitors that you might rather have.
The scenarios where this works are those where all photosynthetic organisms you want are getting enough particulate foods to supply N and P. Most algae types cannot consume particulates, so one can get some corals to thrive in low nitrate/low phosphate situations where algae cannot thrive. The Zeovit method does this, by providing various types of organics (bacteria, perhaps other materials). Not all corals can readily consume particulates foods, so this way to deal with algae is challenging and often fails. I personally think herbivores are much more likely to achieve success.
2. If you are in a high nitrate or high phosphate scenario, and are wondering if lowering levels is needed, take a step back before acting. Polls I’ve run suggest more problems come from lowering these levels than come from the levels themselves. Some fabulous tanks have had phosphate above 1 ppm and nitrate above 100 ppm. That doesn’t mean it’s always a good idea, but it does mean that such levels may not be the cause of the one or two corals you have that show poor polyp extension. Consider other factors as well. If you do proceed to lower them, which is a fine idea, proceed very slowly. Give corals time to adapt their transport capabilities. Plan to do it over weeks, not hours or days for a large drop.
3. Someone who claims a low level of nitrate works great should not be taken as evidence that you can lower it to that level and still be great. They may have far more of other N sources, such as ammonia, flowing through their system. There’s no simple way to test this, but folks who claim heaving feeding or who have lots of fish will necessarily have much more available ammonia than someone who feeds much less. Their corals may just be taking up the ammonia before it becomes nitrate. The same can be true of low phosphate and foods like phytoplankton or bacteria supplying P (and N) to corals.
4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:
I don’t expect this article to reduce the debates about optimal nutrient levels in reef tanks, but I hope it can at least help reefers understand why there is such a debate, and potentially how to wade through it to get suggestions for their own systems.
- Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
- Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
- Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
- Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
- Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
- Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.
Happy Reefing!
Thoughts on Nutrient Target Ranges by Randy Holmes-Farley
Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want high targets, some want a particular ratio, and others just want to know what the heck is going on. Then comes the actions, with many people wanting to raise N and P and many wanting to lower them, and to do either one, aquarists need to wade through a wide range of possible actions. There are great tanks with very low nutrient levels, and there are great tanks with very high nutrient levels. We should not necessarily assume, however, that the same tank would work as well at both extremes of the ranges.
I do not have any magic recipe, or target ranges. While I will give some suggested target values at the end this article, I mostly want to address why so many aquarists have so many different ideas of what is best in their system. In other words, is it rooted in the science of nutrient uptake by corals?
Figure 1. A very high nutrient system maintained by Richard Ross, with nitrate sometimes above 100 ppm and phosphate above 1 ppm. Details in this link:
Rich Ross - Home Tank - guess the phosphate
This tank was built before r2r, here is a link to some links about the build. http://packedhead.net/home-reef/ Current test results: 03-17-2017 Ammonia (NH3-4) Good 0 0.000 - 0.050 mg/L 03-17-2017 Nitrite (NO2) Good 0.006 0.000 - 0.100 mg/L 03-17-2017 Phosphate...
As we get into reasons why aquarists may have different opinions on what works best in their systems, let’s skip over those opinions that come just from reading somewhere what is best. They may be right or wrong, but it’s not so interesting to try to dissect them. Let’s instead focus on real reasons why a given reefer might correctly have an idea what is best in his or her system, and why that correct opinion may differ greatly from that of another aquarist. This information may help reefers focus in on what is best in their system, independent of what anyone else recommends.
1. A first, and very obvious, reason why reefers may have a dispute on what levels are best may be because they keep creatures with different abilities to extract what they need from the same levels of nitrate and phosphate. It is often stated that “soft corals prefer higher nutrient levels”, but how could that be and why would that be true?
First, is it true that different corals prefer different nutrient levels? The simplistic answer appears to be yes, different species have different abilities to collect nutrients (both in a lab and in the field), although comparative data is very sparse. In the natural environment, the distribution of, for example, soft corals vs acropora sometimes appears to relate to nutrient levels. This linked article shows that in some islands in Indonesia, that the preponderance of soft corals is higher in areas of higher nitrate while acropora dominates in higher phosphate locations. Of course there are other factors, and fingering one alone is impossible. Nevertheless, of the factors examined, nutrients appear to be among the best predictors of coral types at the different locations studied.
https://aquapublisher.com/index.php/ijms/article/html/1476
While this acropora vs soft coral differentiation is strong enough to identify in the wild, getting down the species level in terms of wild abundance at different nutrient locations has not been carefully evaluated. Nevertheless, there’s no reason to assume that corals do not vary significantly in their preferences for different nutrient environments for the reasons discussed in the next few sections.
Both nitrate and phosphate are taken up by corals and other organisms using active transporters on their surfaces exposed to the tank water. These transporters are proteins that span some sort of membrane between the coral body interior and the external environment. They bind phosphate or nitrate on the outside, and dump it inside. All organisms have these, from bacteria to people. Organisms control their uptake by adjusting the numbers and types of these transporters, and such effects have clearly been demonstrated in corals. This linked article, for example, shows such control in uptake capacity in the hard coral Stylophora pistillata.
High phosphate uptake requirements of the scleractinian coral Stylophora pistillata
SUMMARYSeveral untested aspects of the regulation of inorganic nutrient uptake were examined using nutrient depletion experiments with the symbiotic coral Stylophora pistillata. The total inhibition of phosphate uptake in artificial seawater lacking sodium indicates the involvement of a...
Indeed, corals that were fed 1 and 3 days before the uptake experiment took up phosphate 42 and 19% slower, respectively, than corals that were fed 21 days before.
…the saturated uptake rate of ammonium increased by 2.5-fold in the presence of 3.0 μmol l–1 of phosphate, thus indicating that the corals or their symbionts were lacking intracellular phosphate to take advantage of the inorganic nitrogen compounds dissolved in their surrounding medium.
There are many such transport proteins, and both the identity and the number of them determine how effectively one organism can take up what it needs relative to another. The upshot is that at, say 0.01 ppm phosphate, one organism may get all it wants while another cannot keep up with its need for phosphate. That is because of the nature and numbers of its uptake transporters in relation to its total need for the transported ion.
The article linked below gives a sense of the complexity and control for phosphate in a single well-studied bacterial system. That level of detailed information is lacking for typical corals we keep.
Molecular Mechanisms of Phosphate Sensing, Transport and Signalling in Streptomyces and Related Actinobacteria
Phosphorous, in the form of phosphate, is a key element in the nutrition of all living beings. In nature, it is present in the form of phosphate salts, organophosphates, and phosphonates. Bacteria transport inorganic phosphate by the high affinity phosphate transport system PstSCAB, and the low...
Nevertheless, there is information on phosphate transport and control mechanisms in corals, such as this article on Stylophora pistillata:
from it:
Our results showed the presence of active phosphate carriers both in the animal and the algal fractions…
Transporters in the animal and the algae presented different affinities for phosphate,…
The velocity of phosphate absorption increased in the light,…
A correlation was found between phosphate uptake rates and the organic or inorganic feeding history of the corals; rates were indeed 4.6 times higher in 8-week starved than in fed corals, and also depended on the repletion status of phosphorus stocks within the symbionts…
The fact that the uptake changed with feeding history means the corals must have changed either the number, or the type, or both, of its phosphate transporters. This result also hints at why it can be very undesirable to lower phosphate too quickly: corals may suffer while they try to ramp up their capability to get what they need from the new, lower level. Likewise with raising nutrients (which seems more of an issue with raising alkalinity too fast, but it’s the same story): corals cannot downregulate their uptake fast enough, and may take inside more of something than is good for them (like a starving person at an all you can eat buffet).
The article linked below even more clearly shows how complicated nutrient uptake can be in corals, with one dinoflagellate symbiont type originally identified from a Montipora verruciosa coral shown to have MANY transporters that it can use, and those may be different than the transporters other corals can use:
https://www.sciencedirect.com/science/article/abs/pii/S0048969720354358
from it:
In addition, this species possesses highly duplicated nutrient transporters including 13 phosphate transporter genes, 62 NO3− transporter genes, and 84 NH4+ transporter genes, which are higher than in other algal species.
Figure 2. A low nitrate system by Reef2Reef member Tusi. When the article was written, he noted phosphate of 0.05 ppm and nitrate of 0.5 ppm. This member may increase bioavailable bacterial foods, which may partly supply some of the N that corals need, by dosing bacteria and carbon dosing.
REEF OF THE MONTH - July 2021: TUSI's Amazing SPS Reef Revisited!
R2R Username: @TUSI Build Thread: Tusi's tank thread Editor's Note: This is the first time in the history of our Reef of the Month that we have revisited a tank that we previously featured. However, we think you will all agree that Tusi's reef is a tank that is highly deserving of this...
2. In addition to different organisms being used by different aquarists to assess what is best in nutrient terms, there are many different endpoints that one reefer may focus on that are different from another reefer, even assessing the same coral and its local environment. Some of these are:
Each of these has its own world of complexity associated with it. Just picking one at random, polyp expansion, we can easily see how one particular aquarist’s assessment of one particular coral may differ from another aquarist with the same coral if there are differences in lighting, flow, fish picking, other chemicals, pH, etc., that all themselves impact polyp expansion. Even if phosphate or nitrate has an effect on polyp expansion, it may be lost as noise under bigger effects of any of these other factors.
- Polyp expansion
- Growth rate
- Color
- Pest algae
- Pest dinoflagellates
- Pest cyanobacteria
- Pest diatoms
- Others
The same sort of variability is true for all of these other endpoints. As another example, the need for available nutrients to prevent dinoflagellate pests in new tanks with bare surfaces may be very different than a mature reef tank with no exposed surfaces where dinoflagellates might take hold. If one way to prevent dino pests is through competition with less troubling organisms occupying the same surfaces, say, bacteria or diatoms or green algae, then that system may benefit from higher nutrients to promote that competition, while other systems without exposed surfaces or with a more mature microbiome may not need those same nutrient levels to avoid dino pests.
3. Another factor that may vary between aquaria is how much N and P a given coral actually needs to grow in a given system. Accepting that factors such as lighting, pH, alkalinity, flow, and trace elements can potentially impact coral growth rates, the rate at which those same corals need to take up N and P will vary with those conditions. Faster growth means it needs more N and P to build new tissues. More need for N and P may mean a different optimal level of nitrate and phosphate in the water to be able to get what it needs. Thus, when one aquarist says 0.03 ppm phosphate gives the best growth, and a second one says no, she sees better growth of the same coral at 0.2 ppm phosphate, the difference could lie in any or all of these and other factors being different between the two systems.
4. Phosphate is known to have a direct and negative impact on hard coral skeleton growth. This linked article, for example, states
… our findings showed that inhibition of coral skeleton formation was due to absorption of phosphate on the skeleton, which inorganically inhibited normal development of juvenile coral skeleton.
https://link.springer.com/article/10.1007/s10126-019-09880-3
The implication of phosphate inhibition of skeletal formation has several implications:
5. Nutrient levels can impact reef tank microorganisms, including coral pathogens, in many different ways. Those microbiome changes may also impact indirect factors relating to corals, such as trace element availability (by microorganism uptake and thus less remaining for corals), and the feeding of corals on those microorganisms.
- Aquarists talking about optimal levels for a hard coral vs soft coral tank may come to different conclusions for this reason alone (perhaps among many others).
- Aquarists talking about only hard corals may be concerned primarily with growth (perhaps implicating elevated phosphate as bad) while others also referring only to hard corals may be concerned with other endpoints, such as color or polyp extension (which may not have the same implications for elevated phosphate)
As an example, this linked article discusses the microbiome effect of nutrients in the context coastal runoff, and suggests that phosphate is a bigger factor than nitrate with respect to one particular coral pathogen expanding in numbers.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8902694/
There are several implications of this microbiome effect of nutrients to the topic at hand.
6. Finally, and very importantly, nitrate and phosphate are far from the only sources of N and P in a reef tank. They may not even be the most used sources. Other sources of N include ammonia (preferred by most corals studied over nitrate), urea (an organic excreted by fish), amino acids, other soluble organics, and particulates including detritus and whole phytoplankton, zooplankton, bacteria and other organisms. Likewise, there are many forms of phosphate available, mostly including dissolved and particulate organics and microorganisms. In fact, the reduced availability of particulate foods in reef tanks is a likely reason that early efforts to mimic ocean levels of nitrate and phosphate in reef tanks led to poor outcomes. We just were not allowing enough N and P availability.
- The effects of nutrient levels on coral health may vary tank to tank based on what microorganisms are naturally present.
- Some of these effects (such as trace element bioavailability) may be “corrected” by dosing needed trace elements or sufficient particulate feeding (such as phytoplankton).
The implications that aquarists need to be critically aware of are:
How to Use This Info
- Nitrate level is a poor indicator of total N bioavailability.
- Phosphate may also not be a good indicator of total P availability
- Claims that, say, 0.5 ppm nitrate is plenty may not extrapolate to any aquarium other than the original one observed for reasons in 1. Same for phosphate.
- Likewise, claims that 10 ppm nitrate is much better than 2 ppm are also difficult to generalize across aquaria for these reasons.
- In general, having a few ppm nitrate may not be needed, or used by corals at all in some systems, but it is insurance that there is sufficient N.
I could drone on and on about these topics, and the discussion would get more and more detached from ordinary reefers experiences, so let’s focus on how one might use the info laid out so far, by looking at some very specific situations.
1. Limiting algae growth by limiting nutrients certainly works, but unless done in special circumstances, it usually risks coral problems from them not getting enough nutrients, or dino problems from them thriving at lower levels than other competitors that you might rather have.
The scenarios where this works are those where all photosynthetic organisms you want are getting enough particulate foods to supply N and P. Most algae types cannot consume particulates, so one can get some corals to thrive in low nitrate/low phosphate situations where algae cannot thrive. The Zeovit method does this, by providing various types of organics (bacteria, perhaps other materials). Not all corals can readily consume particulates foods, so this way to deal with algae is challenging and often fails. I personally think herbivores are much more likely to achieve success.
2. If you are in a high nitrate or high phosphate scenario, and are wondering if lowering levels is needed, take a step back before acting. Polls I’ve run suggest more problems come from lowering these levels than come from the levels themselves. Some fabulous tanks have had phosphate above 1 ppm and nitrate above 100 ppm. That doesn’t mean it’s always a good idea, but it does mean that such levels may not be the cause of the one or two corals you have that show poor polyp extension. Consider other factors as well. If you do proceed to lower them, which is a fine idea, proceed very slowly. Give corals time to adapt their transport capabilities. Plan to do it over weeks, not hours or days for a large drop.
3. Someone who claims a low level of nitrate works great should not be taken as evidence that you can lower it to that level and still be great. They may have far more of other N sources, such as ammonia, flowing through their system. There’s no simple way to test this, but folks who claim heaving feeding or who have lots of fish will necessarily have much more available ammonia than someone who feeds much less. Their corals may just be taking up the ammonia before it becomes nitrate. The same can be true of low phosphate and foods like phytoplankton or bacteria supplying P (and N) to corals.
4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:
I don’t expect this article to reduce the debates about optimal nutrient levels in reef tanks, but I hope it can at least help reefers understand why there is such a debate, and potentially how to wade through it to get suggestions for their own systems.
- Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
- Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
- Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
- Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
- Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
- Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.
Happy Reefing!
@Randy Holmes-Farley I tried to find anything to back this up, but I believed that when nutrients dropped to 0 it takes a long time for tanks to recover. Beneficial bacteria’s starve which allow cyanos and other algaes to take form. My guess is that those than compete with the corals or zooxanthellae. Even when nutrients come back up it takes quite a while for the balance to re establish. Bacteria’s and copepod populations take months to reestablish to appropriate levels.
I think you are underestimating have fast and resilient bacteria are, possibly by a factor only expressed in physics?
You didn’t mention the fuge and GFO running at the same time with oversized skimmer.I also attribute a lot of "0" nutrient tanks to people running roller filters and carbon dosing... but having no clue why, other than somebody told them that is what to do. Of course then they start dumping in N and P to offset that and before you know it have their 3 month old reef upside down....
I don't think the relative cost is much different than it has ever been. I was trying to find what I paid for my reeferrocks.com (same stuff as marcorocks) 20 years ago. It was cheaper than LR For sure, but was still rather expensive, as were the bags of oolitic sand.
My tank and countless others are proof that you can build a healthy reef on dry rock. I do however, firmly believe that starting with all or mostly ocean live rock is exponentially better and a much h faster route to a mature and stable tank. Hitchhikers are a different subject.
At 25% dilution - nitrate is at 235.2ppm!!!OK, I'd try 25% tank water and 75% new salt water, or maybe even 10% tank water. .
At 25% dilution - nitrate is at 235.2ppm!!!
PO4 is at 0.37
Nothing is dying but not growing as fast? Will keep dosing vodka and PhosphateRx to knock down NO3/PO4, respectively.
