Ammonia is our Friend: thoughts needed

[Lasse]

A possible “so what”, and take this as a story, is that a bio filter dominated by ammonia and nitrite oxidation while appropriate for aquaculture and sewage water treatment, it is sub-optimal for a reef aquarium. What might be a characterization of a good bio filter for the reef aquarium is one that cycles nitrogen into biomass which in turns encourages the develop of multiple tropic levels, an overly complex way of saying feeding the coral. This idea could be taken as an elaboration of what the hobby calls creating a mature system or increasing diversity.

Holy cow - please hit the emergency brake. I think that I above have shown that microbial activity create NH3/NH4 in the mineralisation process of organic matter. Below my DSB - there is no fish, no external feeding - its just heterotrophic bacteria breaking down organic matter. In a mature system that have run for years - there is a lot of organic matter and it can always be seen as a potential NH3/NH4 bomb. With all the theories about Old System Syndrom that is drifting around in the hobby - NH3/NH4 and/or H2S explosions are my favorites.

For me - a good nitrification cycle is my safe belt as long as I feed my system with organic matter

Dry rock and corals day one. You can literally load it if you want. Like realistically i say anything. Ive done this with acros and all other types of sps, lps etc.
dose n and p to the right ratios to avoid dinos, keep them low but not too low. Like .01-.03 and like 5 nitrates

Of course - as long as you don't feed your corals (or fish) organic matter - your photosynthesizing corals will act as primary producers - living only on inorganic matter plus light energy. The second you feed something with organic matter (external or internal produced) NH3/NH4 will be produced. Around 20 - 25 % of the organic N in the food will be as new biomass - around 75-80 % will be inorganic N waste ( NH3/NH4)

These paper shows that it is total possible to farm photosynthesizing corals only with light energy and inorganic matters but even in this setup there will probably be inorganic N waste produced from the animal metabolism even if the food is produced inside the animal. However - the setup with an animal and primary producent inside the animal open for a very fast internal recycling of the N waste from the metabolism.

An example with one organic/inorganic loop (feeding fish)

I feed with around 30 g frozen artemia and cyclops every day. Around 4 % of this is protein => 1,2 g protein/day- Around 16 % of the protein is N => 0,192 g N /Day => 192 mg N/day. Around 80 % of this N will be as inorganic N waste in the first loop into the water => around 154 mg N a day out into the water after the first loop (if everything is consumed)

My system is 310 L => =>154/310 mg/L inorganic N => around 0.5 mg N/L. => 0.5 NH4-N/L => 0.64 NH4/L a day-

If this is totally nitrified it will be 0.5 mg/L NO3-N => 2.2 mg/L NO3/day

Summary - if all my added N per day is converted to biomass and the waste is processed by the book - my feeding behaviour will rise the NO3 concentration in my aquaria with around 2 mg/L a day. As my post above shows - if I totally stop my controlled denitrification process - my NO3 concentration rise with around 5 mg/L NO3 and day. 2.5 times higher than the expected worst scenario additions from my way of feeding.

This means that at least 0.67 mg/L NH4-N will be produced internally in my aquarium every day - it also means that my system process at least 1.1 mg/L NH4-N a day in the nitrification process - probably much more if you consider all the processes that take place in a working aquarium.

My aquarium is 310 L => 310 * 1.1 mg = 341 mg N (at least) will be processed daily. Back calculation says that if this should be taken care of in a biomass upbuilding process (other than the initial biomass build up at the first feeding) - my system need to produce around 1.9 g new protein a day => 47.5 g raw biomass a day produced of the waste - of internal and/or external origin - inorganic N in the water

My experiment with NH3/NH4 below the DSB have shown that the NH3/NH4 concentration in the poor water is around 0.4 mg/L NH3/NH4 higher than in my DT. The flow through the bed is around 2000 L a day - it means that around 800 mg NH3/NH4 will be transported through the bed and in some extent out in the DT every day - an addition of 2,5 mg/L if all get out in the aquarium. This is a lot more than my theoretical calculations based on feeding and nitrate measurements - which lead me to consider if there is an Anammox process taking place in the DSB.

However - as I see it - I would not risk to run my present aquarium without doing all I can in order to have a good nitrification process taking place and establish it as soon as possible in a new start if I´m plan to feed my organisms with organic matter.

Sincerely Lasse

 

[Hans-Werner]

Unscientifically lower NO3 leads to paling SPS in my tank with a stable po4 of > .05-.1

1) You should do a trial and take photographs before and with "bleached" corals.

2) Then I suggest to dose ammonium to a calculated concentration of 0.05 ppm twice a day according to instructions by RHF here.

I expect that the corals get dark in 2 or 3 days.

This would show that NO3- is not necessary. Ammonium also has less side effects to other nutrients like iron and phosphate.

3) If 2) doesn't work as expected do a ICP analysis if possible to look for unwanted metals.

Much easier for algae to just pop off a few H atoms. This would of course require non-toxic concentrations of NH3.

Just for your information: From ammonia just one H atom has to be removed to form the amine group. The primary ammonia binding step usually is the formation of glutamin from glutamic acid by adding another amine group.

We do not know if many (for us) troubling micro algae act the same in saltwater.

Zooxanthellae are microalgae. They may use both, ammonia or nitrate but prefer ammonia.

But in normal natural reefs - the N pool is mostly as NO3 as I understand it.

This is not uniform, neither amongst reefs nor in the same reef, see Table 1 CUET, Pascale, et al. CNP budgets of a coral-dominated fringing reef at La Réunion, France: coupling of oceanic phosphate and groundwater nitrate. Coral Reefs, 2011, 30. Jg., S. 45-55.

note: (mmol m-3 = µmol/l)

Now compare these concentrations with the uptake kinetics of Stylophora from Fig. 1 GODINOT, Claire, et al. High phosphate uptake requirements of the scleractinian coral Stylophora pistillata. Journal of Experimental Biology, 2011, 214. Jg., Nr. 16, S. 2749-2754.

You will see immediately that the uptake of NH4+/NH3 is higher at the mean concentrations of 0.13, 0.39 and 0,56 µmol/l than that of NO3- at 0.08, 0.68 and 0.68 µmol/l.

This shows that it is absolutely necessary to always take the uptake kinetics into account to estimate the contribution of a certain nutrient compound at a certain concentration.

FYI, if someone wants to calculate the concentrations in ppb:
1 µmol/l =
(PO4)3-: 95 ppb (0.095 ppm)
NO3-: 62 ppb (0.062 ppm)
NH4+: 18 ppb (0.018 ppm)

 

[aaron186]

Thanks for the comments guys.

Suppose this was the setup. Lets think about a fairly difficult scenario.

1. Dry rock in the water. No display lights yet.

2. Get a refugium or ats or algae rector set up and running.

3. Put some easy corals on the rocks. Fast growing ones preferred.

4. Lights on in the display.

5. N and P dose the tank to feed the corals. Could be nitrate or ammonia or urea for N. Could be a fixed dose, just as one might feed foods, without tracking anything by testing.

6. Slowly expand dosing and organisms. Maybe add in an algae eating fish if needed.

7. As consumers of nutrients expand in numbers, add more producers such as fish, crabs, shrimp, etc

So what things are likely to go wrong, or at least are likely to be worse than dry rock cycling with bacteria additions?

Not necessarily something that could go wrong, but I would say that most people with the reefing skills to pull this off have moved away from fast growing softies. This scenario sounds like a seasoned reefer and not your first time hobbyist. I don’t know too many seasoned reefers who want Xenia or gsp or something “invasive” in their tank. Just a thought though and does nothing to dispute the science

 

[Randy Holmes-Farley]

While I completely agree with that, let me play devils advocate and say, so what!

- I'll just dose some ammonium. It's cheap, easy.
- now i have more filter which gives me greater stability.
- retails happy, now they have 2 products to sell.

That is the question. What can we do to help corals? Dosing ammonia seems helpful. Most people don’t do that, so perhaps they can boost ammonia in other ways (which may also be easier: remonving media). In the case of folks dosing, some ammonia may not be all they want before nitrifiers ruin the party, and this removing media might be better still.

It’s entirely a hypothesis, but not one without some logic behind it.

 

[GARRIGA]

Studied aquaponics as a means of using plants in FW to filter and turns out they still used bacteria.

Perhaps it's not the removal of media as the solution but where the media exists. Live rock might prevent much of the ammonium from reaching corals and not the fact they hold bacteria but that they are present to compete for ammonium when first accessed.

Perhaps non-porous rock with biological media in sump best of both worlds since having bacteria acts as a buffer should system get stressed with more ammonium than corals can consume and skimmer isn't fixing inorganics. In other words, reduce the amount of biological in display giving corals first pass before it gets finished off by bacteria. If nature just wanted plants processing waste than it would have evolved as such my thinking.

Some confusion I'm getting. Are we saying plants prefer ammonia over ammonium or that they can consume ammonia? My understanding being that plants take in ammonium and as that's removed through equilibrium there's less ammonia. This lines up with the understanding that nitrates are down converted to nitrites and then final down conversion to ammonium and not ammonia. Could be wrong. Been a while since I've studied these processes.

 

[Randy Holmes-Farley]

Studied aquaponics as a means of using plants in FW to filter and turns out they still used bacteria.

Perhaps it's not the removal of media as the solution but where the media exists. Live rock might prevent much of the ammonium from reaching corals and not the fact they hold bacteria but that they are present to compete for ammonium when first accessed.

Perhaps non-porous rock with biological media in sump best of both worlds since having bacteria acts as a buffer should system get stressed with more ammonium than corals can consume and skimmer isn't fixing inorganics. In other words, reduce the amount of biological in display giving corals first pass before it gets finished off by bacteria. If nature just wanted plants processing waste than it would have evolved as such my thinking.

Some confusion I'm getting. Are we saying plants prefer ammonia over ammonium or that they can consume ammonia? My understanding being that plants take in ammonium and as that's removed through equilibrium there's less ammonia. This lines up with the understanding that nitrates are down converted to nitrites and then final down conversion to ammonium and not ammonia. Could be wrong. Been a while since I've studied these processes.

That’s a good point that in some tanks, rock porosity may be a detriment.

 

[Hans-Werner]

Are we saying plants prefer ammonia over ammonium or that they can consume ammonia?

Speaking about land plants, plants in the narrower sense, most of them use preferably nitrate as the nitrogen source. For them it is a matter of cation/anion balance in uptake of nutrients. However, there are differences also. In contrast algae prefer ammonium as nitrogen source.

 

[GARRIGA]

Speaking about land plants, plants in the narrower sense, most of them use preferably nitrate as the nitrogen source. For them it is a matter of cation/anion balance in uptake of nutrients. However, there are differences also. In contrast algae prefer ammonium as nitrogen source.

Speaking strictky of water plants which I believe best mimic coral zooxanthella. Same with algae. Based on studies presented in that book by Diana Wadley.

 

[ReeferZ1227]

1) You should do a trial and take photographs before and with "bleached" corals.

2) Then I suggest to dose ammonium to a calculated concentration of 0.05 ppm twice a day according to instructions by RHF here.

I expect that the corals get dark in 2 or 3 days.

This would show that NO3- is not necessary. Ammonium also has less side effects to other nutrients like iron and phosphate.

3) If 2) doesn't work as expected do a ICP analysis if possible to look for unwanted metals.


Just for your information: From ammonia just one H atom has to be removed to form the amine group. The primary ammonia binding step usually is the formation of glutamin from glutamic acid by adding another amine group.


Zooxanthellae are microalgae. They may use both, ammonia or nitrate but prefer ammonia.


This is not uniform, neither amongst reefs nor in the same reef, see Table 1 CUET, Pascale, et al. CNP budgets of a coral-dominated fringing reef at La Réunion, France: coupling of oceanic phosphate and groundwater nitrate. Coral Reefs, 2011, 30. Jg., S. 45-55.

note: (mmol m-3 = µmol/l)

Now compare these concentrations with the uptake kinetics of Stylophora from Fig. 1 GODINOT, Claire, et al. High phosphate uptake requirements of the scleractinian coral Stylophora pistillata. Journal of Experimental Biology, 2011, 214. Jg., Nr. 16, S. 2749-2754.

You will see immediately that the uptake of NH4+/NH3 is higher at the mean concentrations of 0.13, 0.39 and 0,56 µmol/l than that of NO3- at 0.08, 0.68 and 0.68 µmol/l.

This shows that it is absolutely necessary to always take the uptake kinetics into account to estimate the contribution of a certain nutrient compound at a certain concentration.

FYI, if someone wants to calculate the concentrations in ppb:
1 µmol/l =
(PO4)3-: 95 ppb (0.095 ppm)
NO3-: 62 ppb (0.062 ppm)
NH4+: 18 ppb (0.018 ppm)

I am currently dosing that .1ppm 6x per night every 2hrs starting at midnight.

My nitrate appears to be slowly raising/accumulating so i may back down on that dosage, but i also feed very heavy.

An experiment worth performing nevertheless and i may have the opportunity to do so once this 2nd system is setup. Thanks!

 

[Lasse]

note: (mmol m-3 = µmol/l)

Now compare these concentrations with the uptake kinetics of Stylophora from Fig. 1 GODINOT, Claire, et al. High phosphate uptake requirements of the scleractinian coral Stylophora pistillata. Journal of Experimental Biology, 2011, 214. Jg., Nr. 16, S. 2749-2754.

You will see immediately that the uptake of NH4+/NH3 is higher at the mean concentrations of 0.13, 0.39 and 0,56 µmol/l than that of NO3- at 0.08, 0.68 and 0.68 µmol/l.

Correct me if I´m wrong but the first table seems to give µmol/l for the whole molecule but The uptake curves give it in µmol/l N. Because mol is a expression of how many atoms there are of a certain compound - one µmol/l NH4 or NO3 is the same as number as 1µmol/l NH3-N and NO3-N because both compounds contain a single N.

But should we translate this to mg/L - it give a different picture

The first table - if it is the whole molecule - correspond to 0,13*18 = 0.00345, 0,39*18 = 0.007, 0.56*18 = 0.010 mg/L NH4 and 0.08*62 = 0.005 and 0.68*62 = 0,046 mg/L NO3

The graph of N uptake rate shows that at 0.036 mg/L NH4 ( 2 *18/1000) it stabilize a little but for NO3 - it is still a rising rate at around 0.6 mg/L NO3 (9*62/1000)

In a mixed reef with fish and other creatures than corals - I prefer the more safe (in a toxicological point of view for other organism than corals) NO3 uptake.

My measurements of NH3/NH4 in the DT also shows that I already has the NH3/NH4 concentrations that´s are in the fast lane for optimal uptake kinetics

If I would experiment with adding NH3/NH4 - I would not do it before I feel safe with regular testing and today for us non-professional aquarist - the Hanna Marine Master is the only option IMO.

We know that corals can take up NO3. we know that many microalgae can´t. We also know that microalgae prefer NH3/NH4. Why then serve any unwanted microalgae what they want on a silver platter?

In the graph it shows that the uptake rate of N is only around 29 % slower at NO3 around 0.6 mg/L compared with NH3/NH4 at 0.036 mg/L.

I hope I have done the calculations right - please correct me if it is wrong

Sincerely Lasse

 

[Randy Holmes-Farley]

We know that corals can take up NO3. we know that many microalgae can´t. We also know that microalgae prefer NH3/NH4. Why then serve any unwanted microalgae what they want on a silver platter?

In the graph it shows that the uptake rate of N is only around 29 % slower at NO3 around 0.6 mg/L compared with NH3/NH4 at 0.036 mg/L.

I hope I have done the calculations right - please correct me if it is wrong

Sincerely Lasse

How do we know marine microalgae cannot take up nitrate?

 

[Lasse]

we know that many microalgae can´t

This was maybe a too hard statement - should be many benthic microalgae prefer NH3/NH4. This i mainly from experiences with freshwater planted tanks with a lighting similar in strength with a reef tank. Grazers is not common in such tanks and best algae free growth has been when NO3 is used as a N addition. I do not know if it is the same with benthic marine microalgae - but I assume that. Can be right and can be wrong

I tried to update my knowledge of marine benthic microalgae but found very little if anything according preferred N species. But I found this article that´s may interest some of you. This may contradict the assumed high nitrification rate at surfaces in a display tank - at least in the areas that have microalgae growth.

Sincerely Lasse

 

[Dan_P]

I tried to update my knowledge of marine benthic microalgae but found very little if anything according preferred N species. But I found this article that´s may interest some of you. This may contradict the assumed high nitrification rate at surfaces in a display tank - at least in the areas that have microalgae growth.

Several years ago @taricha looked at nitrification in his aquarium. I don’t recall the details. Recently, I began a survey of the top several mm of sand from multiple locations in my aquarium. Since I just started, I will report observations and provide data some other time.

I was surprised to find that only one of seven samples had any ability to convert ammonia to nitrite and nitrate. To @Lasse ‘s point, nitrification may not be wide spread. All seven samples depleted the ammonia in the test solution when acetic acid was present. Only two samples reduced nitrate concentration in the presence of acetic acid.

I wonder what a sand survey would look like for a new system experiencing the uglies or would a sand survey show differences between systems started with dry vs live rock.

 

[mikst]

Not sure what this means, but protein is not needed for many organisms, N and P and other trace elements are.

While I believe that would work well, I’m only talking here about starting the tank that way, but ending with an identical reef tank with all your favorite organisms.

I would argue it's 6 of one half a dozen of another. Proteins, come from amino acids, come from base elements, such as the nitrogen you mention. And of course carbon , hydrogen, and oxygen. I'm pretty sure you know this based on your pedigree. I think the term "protein" is overused in language today, both culinary and aquaristlike. And yes of course all the other trace elements get consumed in various form with P and K in limited amounts. Addition of food brings in a wide range of all these elements. Some in higher carbon/carbohydrate amounts and some heavier in protein. They both have their areas of need. Maybe you want your water column higher on P, so you feed your gildren food X. Maybe you want it higher in N in comparison to carbon, food Y.

Anyway, you don't have to convince me that ammonia is good. Saying ammonia is bad is like saying dihydrogen monoxide can be lethal. Context is important. I really liked the hurricane and earthquake analogy. Same goes for forest fires.

I'm lagging behind in the conversation so I'm sorry if above has been stated before.

 

[SDchris]

I was surprised to find that only one of seven samples had any ability to convert ammonia to nitrite and nitrate.

If ammonia was accumulating in the sediment, for what ever reason, would it be reasonable to conclude that if diffusion / gradients are at play, the majority would end up going back to the sediment/water interface and bulk water column?

 

[Bodo Reed]

I'm thinking of wring an article on how ammonia has been wrongfully vilified in our hobby, with plenty of ammonia science and literature data, experiences of folks dosing it, etc.

One possible part of it relates to the whole idea that one could start a reef tank without intentionally cycling nitrifiers. No bacteria additives, not sponges or whatever. Live rock is fine, but the goal of it is to have surfaces resistant to algae, not to add bacteria.

For example, starting with plenty of macroalgae, soft corals, and coralline right from day or week one. No fish, or perhaps only an algae eating fish , etc.

The simplistic idea is to have as much or more ammonia uptake capacity than is added from organism feeding. Seems inherently logical, but I'm not certain if there are hidden issues.

This thread is a pre-article idea generating thread to flesh out ideas and problems before writing the article.

All thoughts and ideas are welcome, especially if you do not agree with the premise or believe the concept will fail.

Hey Randy Im operating I giant tank 1650 and Im a fan of yours , this ammonia thing surprised me a lot was kind of tryin to understand , so I cant have a say , but very interesting topic , followin with great interest as a student , my tank , hoppe u like it , have a great day

 

[Garf]

I think the only addition I can make to this thread is to note that my tank rock is non porous rock, bare bottom, no skimmer. I have detected the presence of low levels of ammonia, it still readily produces nitrate, always has. I've seen all of the expected delays, compared to live rock.

 

[Hans-Werner]

But should we translate this to mg/L - it give a different picture

This doesn't matter at all since one mol N is one mol N is one mol N, no matter what the molar weight of the compound is. You only can judge the preferred N-compound in mol N.

The graph of N uptake rate shows that at 0.036 mg/L NH4 ( 2 *18/1000) it stabilize a little but for NO3 - it is still a rising rate at around 0.6 mg/L NO3 (9*62/1000)

Correct, but we are not discussing whether nitrate concentration should be higher or lower than 1 ppm. The nitrate concentrations that are generally discussed are a completely different league.

My measurements of NH3/NH4 in the DT also shows that I already has the NH3/NH4 concentrations that´s are in the fast lane for optimal uptake kinetics

So why have nitrate also? Nitrate as a precursor of NH4? You can turn it and twist it as you like, it doesn't really make sense.

The only thing that is still interesting to me is whether high nitrate concentrations really have other effects than the function as a nutrient and I am quite sure it has. I am convinced there are more direct ways to get the same effect.

I think that the main function of high nitrate concentrations is keeping iron oxidized. There are proponents of high nitrate concentrations also recommending regular iron supply. In their world both makes sense. Viewing the bigger picture it maybe doesn't make sense.

 

[Lasse]

Anyway, you don't have to convince me that ammonia is good. Saying ammonia is bad is like saying dihydrogen monoxide can be lethal.

It all about the circumstances - as an example - if you have 300 m of dihydrogen monoxid above you, no scuba or other technical things - your in trouble

If ammonia was accumulating in the sediment, for what ever reason, would it be reasonable to conclude that if diffusion / gradients are at play, the majority would end up going back to the sediment/water interface and bulk water column?

Inorganic N is not stored as NH3/NH4, NO2, NO3 in the sediment. The only inorganic N i know of that can be stored in small quantities in the water is N2. However organic N is stored in dead organic matter or in living matter in your aquarium. This "storage" of organic N will be converted into inorganic N by bacteria or by the metabolism of living organisms (as waste). First step in that transformation/transportion out into the water is NH3/NH4. Hence - diffusion/gradients is not actual.

So why have nitrate also? Nitrate as a precursor of NH4? You can turn it and twist it as you like, it doesn't really make sense.

In most cases I do not see nitrate as a precursor of NH4 - I see it as a successor. There is bacteria that convert NO3 directly into NH3/NH4 and you can say that the waste of NO3 in photosynthetic activity is NH3/NH4 but nevertheless - the N circulation for me start with the processing of organic matter.

For me that have an older aquarium with both a heavy load of fish and other invertebrates than corals together with a lot of corals - its important to play on the safe part of the field. NO3 as inorganic N source and major inorganic N pool in the water that is non toxic for the most of my living creatures. It has also been shown (in the waste water industry) that NO3 concentrations above 2 mg/L in the water and sediment block or at least delays the forming of another deadly gas in a closed system - hydrogen sulphide (H2S). My system allows me to more or less zero my NO3 concentration - if I want. However - every time I chose to do that - I run into other problems - mostly the forming of cyanobacterial mats.

I think that the main function of high nitrate concentrations is keeping iron oxidized. There are proponents of high nitrate concentrations also recommending regular iron supply. In their world both makes sense. Viewing the bigger picture it maybe doesn't make sense.

Maybe your right - maybe not. But for me - the bigger picture is to decide what you want with your aquarium. If you want a coral garden of coloured sticks with low bioload of heterotrophic organism beside the heterotrophic part of corals partnership - maybe oxidation of iron is the most important issue. If you - like me - want a more diverse aquarium with a lot of both corals and fish - the bigger picture include different issues and different decisions.

For example, starting with plenty of macroalgae, soft corals, and coralline right from day or week one. No fish, or perhaps only an algae eating fish , etc.

The simplistic idea is to have as much or more ammonia uptake capacity than is added from organism feeding. Seems inherently logical, but I'm not certain if there are hidden issues.

Of cause - this will work - as long as you match your external feeding behaviour with the amount of photosynthetic activity. But - IMO and IME - if you once have build up a nitrification capability in a system - especially the second step - even if your actual nitrification rate goes down (low availability of NH3/NH4 for nitrification) the time it takes from low nitrification rate to high is lesser than the time it takes if you go from a situation with no earlier working nitrification cycle. I admit that my experiences of this is mostly from the freshwater side - but on the other hand - I have a lot of experiences handling nitrification in both fresh water aquaria, waste water treatment plants and recirculated fish farms (RAS systems)

As you can see in my article 15 steps - its build on nearly the same ideas but include a slow upbuild of the nitrification capacity.

If you have not read the article I linked to in an earlier post - please do that - I think it will give you some ideas or thoughts.

The authors conclude

Our data indicate that direct competitive interaction takes place between algae and AOB and that benthic algae are superior competitors because they have higher N uptake rates and grow faster than AOB

Can it be the same for the corals zooxanthella versus AOB? It could explain @Dan_P :s experiences in post 153

Sincerely Lasse

 

[Hans-Werner]

For me that have an older aquarium with both a heavy load of fish and other invertebrates than corals together with a lot of corals - its important to play on the safe part of the field. NO3 as inorganic N source and major inorganic N pool in the water that is non toxic for the most of my living creatures. It has also been shown (in the waste water industry) that NO3 concentrations above 2 mg/L in the water and sediment block or at least delays the forming of another deadly gas in a closed system - hydrogen sulphide (H2S). My system allows me to more or less zero my NO3 concentration - if I want. However - every time I chose to do that - I run into other problems - mostly the forming of cyanobacterial mats.

This is exactly what I am talking about: You have a high bioload. So why should it be necessary to dose any nitrogen at all? I mean, dosing nitrate does not make the ammonium disappear. If the ammonium would disappear you would most likely run into problems with the corals despite or exactly because having nitrate. Nitrate is ok as long as it is not the only nitrogen source - quite a paradoxical situation. As soon as nitrate is the only N source it will hurt the corals (scientifically proven and own experience).

Finally, the effect of nitrate to inhibit cyanobacterial growth cannot be explained with N - no way. The effect of nitrate is to keep iron oxidized and inhibit cyanobacterial growth in this way. Cyanobacteria have a high demand for iron.

Dosing nitrate will not lower ammonium in your tank but rather increase it. So it is no explanation that the cyanobacteria or other microalgae wouldn't get ammonium for growth. This is what I mean when I say, there are more direct ways, at least often there are. But it is absolutely necessary to have the right explanation first to find these more direct ways.