Nitrates — is my eyeball method crazy?

[MnFish1]

BTW - when people say 'they don't do water changes' - each time they replace their skim mate, each time they adjust their salinity - using RODI - or mixed seawater - they are doing a 'water change' - One person wrote - I usually siphon off 5% of my detritus/water each week - or so - depending - thats a water change. As Randy Holmes Farley has shown - even small water changes make various chemicals reach a lower equilibrium point than if nothing was done. PS - I wonder - for all the people who dont do 'routine' water changes (I think I'm in that camp) - when you get your ICP and something is high - how do you correct it? If its a water change - you're doing water changes

 

[jccaclimber]

I have heard that many people say 'hair algae will kill coral' - to me its the opposite - coral covering a tank - will rarely have a GHA problem - but if you take a 200 gallon tank - put in a lot of surface area - and 10 dime sized frags - something is going to grow on the rock.... Or am I all wet

Works both ways. I had an issue with an easy cyphastrea recently, dying off on one side. I killed off the hair algae just upstream of it and suddenly it immediately started recovering. There is of course more to it because I have a frag of the same coral elsewhere in the tank where the algae was up against it on all sides, and yet the coral was slowly gaining ground. I'd guess that a coral in great health can push back algae (I've seen acros send out filaments and dissolve bryopsis as they grow), but that the algae is still a negative, and can win when conditions are marginal.

I've definitely seen what you are saying. The easiest way for me to keep algae off of a rock is to cover it in an encrusting coral.

 

[jccaclimber]

BTW - when people say 'they don't do water changes' - each time they replace their skim mate, each time they adjust their salinity - using RODI - or mixed seawater - they are doing a 'water change' - One person wrote - I usually siphon off 5% of my detritus/water each week - or so - depending - thats a water change. As Randy Holmes Farley has shown - even small water changes make various chemicals reach a lower equilibrium point than if nothing was done. PS - I wonder - for all the people who dont do 'routine' water changes (I think I'm in that camp) - when you get your ICP and something is high - how do you correct it? If its a water change - you're doing water changes

I've been in that camp (not currently, but will be again someday). Even when I was "not doing water changes and had no skimmer I was averaging (rough guess) 2 gallons per week selling macro, using it in my bandsaw making frags, transporting frags, etc. That worked out to ~15% of my system volume over the year (admittedly not the same as a single 15% WC). Once I started skimming that went up ~15% due to skimmate replacement.

 

[Tired]

Hair algae can eventually cause some problems to corals by growing on them, but healthy corals can tolerate a decent bit of it.

It's definitely possible to use various factors in your reef tank to monitor nitrates. Partly because nitrates really don't need to be precisely measured- I don't know why anyone bothers getting it down to exact portions of PPM. Do you have something between 5 and 20 ppm nitrates? You're good. Some tanks run fine with more than that. Less is probably not a good thing.

 

[MabuyaQ]

On the reef nitrate is extremely low - yet there is algae. How?

Because that low level of nitrates is guaranteed by mother nature 24/7/365. Unlike aquariums a reef is a a self sustaining ecosystem where there is an equilibrium state. Nutrient levels in an aquarium completely depend on external inputs these inputs drive the fluctuations in measurable nutrient levels as well. So unless there is an external input 24/7 at low measurable levels these fluctuations could result in the unnatural situation where there are no nutrients at all. By creating a stable somewhat elevated level such an effect these fluctuations can have will be mitigated.

 

[Lasse]

I cannot imagine how you could kill things with too low of nitrate if you have a lot of nitrate going in.

You are right that it is the flux that is the most important factor here - not the concentration of the not used nutrients. However the problem for me is if I have zero in nutrients in the water column - I can only know when my flux is to strong - not when it is to low because I can´t measure below 0. But if I aim for - let us say 0.05 mg/L PO4 and 3 mg/L NO3 - I will also see when the flux it too small. For me - it is not more complicated than that. If my eyes say that it works - the left over nutrients is stable - no worries

Sincerely Lasse

 

[Randy Holmes-Farley]

You are right that it is the flux that is the most important factor here - not the concentration of the not used nutrients. However the problem for me is if I have zero in nutrients in the water column - I can only know when my flux is to strong - not when it is to low because I can´t measure below 0. But if I aim for - let us say 0.05 mg/L PO4 and 3 mg/L NO3 - I will also see when the flux it too small. For me - it is not more complicated than that. If my eyes say that it works - the left over nutrients is stable - no worries

Sincerely Lasse

You also cannot know where it is going just from overall flux. It may all be going into the organisms with the most capable uptake transporters, and none into others.

 

[KenRexford]

You also cannot know where it is going just from overall flux. It may all be going into the organisms with the most capable uptake transporters, and none into others.

I think that everyone probably has the same experience informing us, though. If lowering nitrates by whatever means kills nuisance algae before killing corals, then the corals must be the most capable organisms in the tank. That part seems obvious. Otherwise nuisance algae would be a necessary byproduct of a flourishing reef tank. We know that this is not the case, so the corals must be the winners.
We also seem to know that macro algae needs a boost to outcompete nuisance algae. Hence the refugium and refugium lights. So, it seems that most algae micro or macro are on the same playing field, all else equal.
We also know that bacteria wins over algae. Bacteria seems to win out over corals but only if fed sugars, so we can control them better than algae.
This seems to suggest a fairly known hierarchy of uptake capacity, algae weakest, then corals, the super-fed bacteria. If that’s true, then the best test kit might not be a nitrate test but a bacterial population test, like used for hot tubs. This might mean a cuetip swab of the inside glass of the tank?

 

[92Miata]

I think that everyone probably has the same experience informing us, though. If lowering nitrates by whatever means kills nuisance algae before killing corals, then the corals must be the most capable organisms in the tank. That part seems obvious.

This has not been my experience.

There are nuisance algae that can fix nitrogen gas, and nuisance algae that catch food, and nuisance algae that can dissolve aragonite to pull phosphate out of it.

In my experience - crashing nutrients kill corals way faster than they kill algae.

 

[jccaclimber]

I think that everyone probably has the same experience informing us, though. If lowering nitrates by whatever means kills nuisance algae before killing corals, then the corals must be the most capable organisms in the tank. That part seems obvious. Otherwise nuisance algae would be a necessary byproduct of a flourishing reef tank. We know that this is not the case, so the corals must be the winners.
We also seem to know that macro algae needs a boost to outcompete nuisance algae. Hence the refugium and refugium lights. So, it seems that most algae micro or macro are on the same playing field, all else equal.
We also know that bacteria wins over algae. Bacteria seems to win out over corals but only if fed sugars, so we can control them better than algae.
This seems to suggest a fairly known hierarchy of uptake capacity, algae weakest, then corals, the super-fed bacteria. If that’s true, then the best test kit might not be a nitrate test but a bacterial population test, like used for hot tubs. This might mean a cuetip swab of the inside glass of the tank?

My experience disagrees, but with an "It depends".

Case 1.
In a situation with high particulate food (live or otherwise) that is not simply settling and decomposing in the algae, the coral will be able to utilize that, the algae will not. Coral wins as free floating nitrate is removed. This is the situation on a real reef, and perhaps in an established tank with good diversity as well.

Case 2.
A situation without those non-free nitrogen sources of food. If the coral is relying on free nitrate (ie not bound into a particle or organism) then the "level to sustain coral" is > than the "level to sustain algae". Coral loses. Algae wins.

Case 3.
No particulate food, no free nitrate. Cyano bacteria can fix their own nitrogen and will win. Everything else will eventually starve or get over-run by the cyano.

Case 4.
Case 3, or pretty close to it, but with a phosphate shortage as well. Dinos might win. Coral and other algae still loses.

Algae vs. bacteria winning in other cases is dependent on carbon availability and other things, not just nitrate levels.

 

[Lasse]

Otherwise nuisance algae would be a necessary byproduct of a flourishing reef tank. We know that this is not the case, so the corals must be the winners.

That´s not IMO. Microalgae will always be in a reef tank despite on nitrate levels - there is clear evidences that many micro algae not even can use nitrate as an inorganic N source - they need NH3/NH4 instead. Ask the people that is skill in freshwater planted tanks - many of them use nitrate as nitrogen source instead of NH3/NH4 just because of not favour microalgae. Microalgae is a necessary byproduct of a flourishing reef both in nature and in captivity. The thing that control these are the grazers - what we in normal reef language name CUC.

Further on - if you with the word nuisance algae even mean cyanobacteria and incorporate dinoflagellates (an micro algae) in this word - your wrong again (IMO) Outbreak and monocultures of these organisms seems to be linked just to very low (or zero) nutrients (leftover) in the water column - because they have other tricks to get these nutrients.

Sincerely Lasse

 

[Belgian Anthias]

Because skimmers do far more useful things that control nutrients. I would run one for aeration alone.

How good is a skimmer as an aerating device?
The gas exchange capacity is very small due to the small contact area with the water surface. If the water is saturated of different gasses and is low on oxygen, how a skimmer may become a good aeration device?

 

[Lasse]

How good is a skimmer as an aerating device?
The gas exchange capacity is very small due to the small contact area with the water surface. If the water is saturated of different gasses and is low on oxygen, how a skimmer may become a good aeration device?

Is the best if you do not have space for a good height rissler filter. The modern skimmers with small bubbles and rather long retention time give a gas exchange that is proportionally to the area of the combined interface between ait (in the bubbles) and water. More or less the same gas exchange as an open surface of water. You can incorporate the interface area from each of the micro bubbles in the calculations and the retention time is the time a bubble is in the water.

The old wooden airstones did not give enough small bubbles for this exchange. In the 90:ties - I did experiments with membran aerators in sewage treatment. The gas exchange from these bubbles (in the water) was as high as in a rissler filter. Note - that bubbles from a membrane aerator is larger than those from a modern venturi skimmer. I also use an overdosed skimmer as an gas exchanger.

Prove for this is the huge capacity for CO2 scrubbed air (in the inlet of the skimmers air intake) to remove CO2 from the water, hence rise the pH and the fast effect on aquarium pH if the amount of people in the room (with an aquarium with a skimmer) differ, hence the CO2 in the air changes

Sincerely Lasse

 

[KenRexford]

I don’t for the life of me understand any of this theory stuff. On the one hand, we are talking about the different sources of nitrates, whether particulate or free floating. Particulate is not likely tested in a tester, so why does the test matter if you feed your fish and corals? Who has a tank that omits feeding? Then, we need to know what form of nitrates, but does the tester tell me a ratio of Nitrate to NH3/NH4? If corals gran particulates, but algae grabs not Nitrate but NH3/NH4, then why on earth is the level of free-floating Nitrate relevant to anything? Seems like your best bet ends up being eradication of any generally noticed free floating nitrate, because no critter cares about that, or mostly algae. Then feed a lot. That’s a big “no kidding.” ULN with lots of fish and food and reef roids and aminos. Bacteria to get to the leftovers before the algae. Let the cyano runs its course. Then have an established tank. Once you get there, the same question recurs—why does level of free floating nitrates matter if your nitrogen source for the corals is primarily food? And, if free floating nitrates are not bad, then why does heavy import of food and heavy export of free floating nitrates work?
I mean, this seems so simple from my experience, but maybe I am insane. If I have lots of fish, feed them, add roids, add ab+, and keep nitrates down with refugium and maybe vibrant when needed, great fish, great corals, barely struggling algae stumps, no cyano, happy tank. If I don’t feed all this stuff and keep nitrates down, everything suffers. If I don’t feed but let nitrates rise, algae comes back with a vengeance. I cannot speak for others, I guess, but maybe there are different needs for different populations of fish or maybe for more sps dominated tanks? Mine is mixed, with anything from softies through sps, with extreme softies suffering (can’t keep mushrooms strangely) but all others thriving.

 

[Lasse]

we are talking about the different sources of nitrates, whether particulate or free floating

Nitrate is an organic form of nitrogen - NO3 and it is the rest product from nitrification. In an aquarium - the only source for nitrate is the nitrification process

hen, we need to know what form of nitrates, but does the tester tell me a ratio of Nitrate to NH3/NH4?

There is only one form of nitrates in the watercolumd - the NO3 ion

free-floating Nitrate

What is that? Nitrate is dissolved in water - it is an ion

Can it be that way that you mix up nitrate and nitrogen with each other?

Most macro algae, zooxanthellae and some microalgae can use nitrate as an nitrogen source. Some bacteria use nitrate as electron acceptor in their metabolic process.

As a tip - if you have missed it - many corals live in symbiosis with an algae (zooxanthellae) and this algae can use inorganic nitrogen in the water - among them nitrate. These zooxanthellae give the coral animal energy - they do not need to ate as much as the corals without zooxanthellae.

Sincerely Lasse

 

[Randy Holmes-Farley]

I think that everyone probably has the same experience informing us, though. If lowering nitrates by whatever means kills nuisance algae before killing corals, then the corals must be the most capable organisms in the tank. That part seems obvious. Otherwise nuisance algae would be a necessary byproduct of a flourishing reef tank. We know that this is not the case, so the corals must be the winners.
We also seem to know that macro algae needs a boost to outcompete nuisance algae. Hence the refugium and refugium lights. So, it seems that most algae micro or macro are on the same playing field, all else equal.
We also know that bacteria wins over algae. Bacteria seems to win out over corals but only if fed sugars, so we can control them better than algae.
This seems to suggest a fairly known hierarchy of uptake capacity, algae weakest, then corals, the super-fed bacteria. If that’s true, then the best test kit might not be a nitrate test but a bacterial population test, like used for hot tubs. This might mean a cuetip swab of the inside glass of the tank?

That is definitely not always the case. It used to be assumed the only a few problem algae deviated from that (such as bryopsis), which is why I and others did recommend reduced nutrients to control algae for decades, but it has since become clear that reducing nutrients does not always (or even often)s beat algae before harming corals.

 

[Randy Holmes-Farley]

How good is a skimmer as an aerating device?
The gas exchange capacity is very small due to the small contact area with the water surface. If the water is saturated of different gasses and is low on oxygen, how a skimmer may become a good aeration device?

They can be very good.

In my tank, using limewater for all calcium and alkalinity, removing it as an experiment caused the pH to rise substantially.

Also, in Eric Borneman's O2 articles, he experimentally showed it increased O2 saturation.

http://reefkeeping.com/issues/2005-08/eb/index.php

" Airstones and skimmers appear to be a very effective means of oxygenating small water volumes. "

 

[Lasse]

why I and others did recommend reduced nutrients to control algae for decades, but it has since become clear that reducing nutrients does not always (or even often)s beat algae before harming corals.

And there was people in another thread that say that you could not change your mind and admit it This proven him wrong

Thank you for this clarification

Sincerely Lasse

 

[MabuyaQ]

I don’t for the life of me understand any of this theory stuff. On the one hand, we are talking about the different sources of nitrates, whether particulate or free floating. Particulate is not likely tested in a tester, so why does the test matter if you feed your fish and corals? Who has a tank that omits feeding? Then, we need to know what form of nitrates, but does the tester tell me a ratio of Nitrate to NH3/NH4? If corals gran particulates, but algae grabs not Nitrate but NH3/NH4, then why on earth is the level of free-floating Nitrate relevant to anything? Seems like your best bet ends up being eradication of any generally noticed free floating nitrate, because no critter cares about that, or mostly algae. Then feed a lot. That’s a big “no kidding.” ULN with lots of fish and food and reef roids and aminos. Bacteria to get to the leftovers before the algae. Let the cyano runs its course. Then have an established tank. Once you get there, the same question recurs—why does level of free floating nitrates matter if your nitrogen source for the corals is primarily food? And, if free floating nitrates are not bad, then why does heavy import of food and heavy export of free floating nitrates work?
I mean, this seems so simple from my experience, but maybe I am insane. If I have lots of fish, feed them, add roids, add ab+, and keep nitrates down with refugium and maybe vibrant when needed, great fish, great corals, barely struggling algae stumps, no cyano, happy tank. If I don’t feed all this stuff and keep nitrates down, everything suffers. If I don’t feed but let nitrates rise, algae comes back with a vengeance. I cannot speak for others, I guess, but maybe there are different needs for different populations of fish or maybe for more sps dominated tanks? Mine is mixed, with anything from softies through sps, with extreme softies suffering (can’t keep mushrooms strangely) but all others thriving.

There are several papers that show when healthy patches of reef are closed of from herbivors algae take over to the point that they end up killing corals. https://onlinelibrary.wiley.com/doi/full/10.1002/ece3.3620 So it are the herbivors that control algae, therby mitigating the effect that algae outcompete corals, even at the much lower nutrient levels found in nature.

 

[Belgian Anthias]

My experience disagrees, but with an "It depends".

Case 1.
In a situation with high particulate food (live or otherwise) that is not simply settling and decomposing in the algae, the coral will be able to utilize that, the algae will not. Coral wins as free floating nitrate is removed. This is the situation on a real reef, and perhaps in an established tank with good diversity as well.

In the case, we talk about TOM ( total organic matter) and not about nitrate but nitrogen, TOM of which the nitrogen content for +- 85% will be turned into ammonia-nitrogen after digestion ( remineralisation and dissimilation), to be used by algae and other organisms. Wich means from total TOM removed a lot more nitrogen becomes available for algae and other growth as used up by the coral.

Case 2.
A situation without those non-free nitrogen sources of food. If the coral is relying on free nitrate (ie not bound into a particle or organism) then the "level to sustain coral" is > than the "level to sustain algae". Coral loses. Algae wins.


Corals have their own holobiont, taking up inorganics to produce protein, providing organic nutrients to the coral. The Symbiodinium may provide the energy source. Why algae should win? A coral with symbiodinium does not need to be fed organics to fullfill its need for organic nutrients. The coral may manage its nutrient suply by managing the growth rates in its own holobiont by providing an organic carbon source and other nutrients by releasing mucus. The carbon is fixed by symbiodinium into suggars, used for energy production. Corals do not like an environment with high DOC availability as they may not be able to mange the holobiont growth rates as desired. in a normal situation DOC is used up fast as it is limited available because most of the carbon is released as CO2. I think corals have nothing to fear in the competion for nutrients with algae using nitrate as a nitrogen source.

Free available nitrogen is ammonia-nitrogen already present in the water column which is toxic. The production of ammonia-nitrogen from TOM is not free at all as a lot of energy was needed to produce DOC, for respiration, dissimilation, the production of CO2, phosphate and ammonia.
Almost all microorganisms prefer ammonia-nitrogen as a nitrogen source for growth, most inhibit the use of nitrate-nitrogen if ammonia-nitrogen is available. A lot of algae are able to use both ammonia and nitrate if ammonia is limited available and are able to use both pathways at the same time. If using nitrate growth rates are slowed down and is often used only to support the cells, waiting for ammonia-nitrogen to induce growth. As most stony corals are supported by is symbiodinium and holobiont for there energy source and nutrient supply they do not depend much of what you call "the level to sustain". My opinion, there is no such level, only when there is not enough or in the case of to much DOC . But something must limit growth and in most cases, it is the growth rates creating unavailability. High growth rates are linked to the availability of organic carbon and the use of ammonia as a nitrogen source. It is not the level of nitrate present in the water column which will be responsible for the growth rates wich may lead to phosphorus starvation, it will be the demand on that place where the action and competition take place. Biofilms, microbial mats, coral holobionts, etc.. are able to manage there own food supply for a long period of time without what you call " non free nitrogen sources of food". A coral holobiont loses that ability in an environment with high DOC availability. This means DOC management seems to be a lot more important compared to nitrate management as nitrate does not harm a thing, except at very high levels.
The nutrient level does NOT influence growth rates, it is availability. The use of nitrate slows down the growth of algae. The coral is supplied ammonia by its holobiont. Why algae may win using nitrate as a nitrogen source?

Case 3.
No particulate food, no free nitrate. Cyano bacteria can fix their own nitrogen and will win. Everything else will eventually starve or get over-run by the cyano.

There is no such thing as free nitrate. Nitrate is the end product of aerobic remineralization.
To produce nitrogen usable for growth a lot of energy is needed. Transforming nitrate into for growth usable nitrogen needs a lot more energy. Fixing nitrogen even more. Also cyano prefere ammonium-nitrogen and will inhibit nitrogen fixation if other nitrogen pathways are available.
Food starved organisms provide nutrients for others. What is the growth-limiting factor? I prefer it to be nitrogen if I had the choice.
Organisms grow at a logarithmic rate and die a natural death at a logarithmic rate.
Not all cyano can fix nitrogen and also some other organisms have the ability to fix nitrogen. They only fix nitrogen if there is no other nitrogen source available as fixing nitrogen is very expensive needing a lot of energy. But they have an unlimited carbon and energy source not depending on availability in the water.
In microbial mats, the nitrogen source is provided by natural remineralisation within the biofilms. In these conditions, cyano may support the microbial mat in a nitrogen limited environment. Cyano and other nitrogen-fixing organisms are very important members of the coral holobiont.
In the ocean, they play an essential role in the nitrogen cycle and as a food source, as a member of phytoplankton. Cyano is very effective in storing phosphorus and most of them are able to fulfill 5 cycles based on their phosphorus reserve. One does not want both, phosphorus- and nitrogen-limited conditions in a reef aquarium.

Case 4.
Case 3, or pretty close to it, but with a phosphate shortage as well. Dinos might win. Coral and other algae still loses.

Phosphorus unavailability is a killer on short notice. That is why most organisms are able to store a phosphorus reserve. Bacteria known as PAO contain a very high phosphorus reserve which they may release in nitrogen-limited conditions. Symbiodinium are dino's!
Nobody will win from phosphorus shortage but PAO ( phosphate accumulating organisms) , including cyano, will support microbial communities wich may recycle phosphorus, enough to support the comunity for a period of time. Dying microbial communities are the messenger for a lot worse. Algae may loose +50% of their weight for supporting the comunity. Will dino's win? As members of a microbial comunity or member of phytoplankton?

Algae vs. bacteria winning in other cases is dependent on carbon availability and other things, not just nitrate levels.

It has been shown nutrient levels do NOT influence growth rates. It is availability. Total growth of coarce will be influenced by total availability. The availability of DOC, and the available nitrogen source used will be determent for wich organisms will be dominant at that moment. Heterotrophic bacteria, r-stratigists, will always out-compete other organisms for ammonia-nitrogen in the water column if usable DOC is available, certainly when carbohydrates are added. When using nitrate most photo-autotrophic organisms, having a free energy source, will be very competitive for the available sources. Heterotrops will use up natural available DOC anyway. Other autotrophs, AOB, NOB, AOA, will be outcompeted if not in a protective environment. Adding organic carbon will replace the autotrophs by heterotrophs.

As we are able to manage the availability of the usable nitrogen source and are able to manage aerobic and anaerobic remineralization , using a biofilter, we have the ability to manage the growth rates as desired and limit growth based on the nitrogen availability, wich my opnion is the prefered growth limiting factor.