What is the nitrite concentration of your mature reef? And why it may matter.

[KGV]

I known it may not affect the animals in your aquarium, but measurable nitrite will affect the amount of NO3 that you measure (depending on the test that you use).

I have a 1.5 year-old reef and I measure 0.150 ppm nitrite (Hanna ULR). I was surprised it was this high. This means that for some NO3 tests, for example Tropic Marin, 0.150 ppm nitrite will account for 15 ppm of measured NO3. And if you measure 15 ppm NO3 with the Tropic Marin test, there may actually be no NO3 in your system at all. If you grow Acropora, perhaps you decide to take drastic measures to get the NO3 value down by reducing your feeding and create a major problem.

Very few measure nitrite once the tank is matured. Perhaps we should? Is my 0.150 ppm nitrite high, indicating a problem with the nitrification cycle? Could high nitrite be typical for tanks with heavy feeding? I grow acros and use heavy in/out, with no supplements but kalk and 2-part.

@Lasse @Hans-Werner @taricha. Am I correct? Any thoughts?

 

[blaxsun]

It's an interesting thought - and you're right, I probably haven't tested for nitrite in well over a year. The next time I'm doing my nitrate test I'll throw a nitrite test in just to see where it's at.

 

[damsels are not mean]

I don't know that I've even touched a nitrite test in like 10 years. I haven't cycled tanks since my initial ones both fresh and saltwater because I'd just move rocks over.

 

[Garf]

I known it may not affect the animals in your aquarium, but measurable nitrite will affect the amount of NO3 that you measure (depending on the test that you use).

I have a 1.5 year-old reef and I measure 0.150 ppm nitrite (Hanna ULR). I was surprised it was this high. This means that for some NO3 tests, for example Tropic Marin, 0.150 ppm nitrite will account for 15 ppm of measured NO3. And if you measure 15 ppm NO3 with the Tropic Marin test, there may actually be no NO3 in your system at all. If you grow Acropora, perhaps you decide to take drastic measures to get the NO3 value down by reducing your feeding and create a major problem.

Very few measure nitrite once the tank is matured. Perhaps we should? Is my 0.150 ppm nitrite high, indicating a problem with the nitrification cycle? Could high nitrite be typical for tanks with heavy feeding? I grow acros and use heavy in/out, with no supplements but kalk and 2-part.

@Lasse @Hans-Werner @taricha. Am I correct? Any thoughts?

Absolutely. I think most folks will be surprised to hear that just as nitrite interferes with nitrate tests, aminos actually interfere with the nitrite readings in some tests (actually reads lower than the real value), which confuses things even further.

 

[Randy Holmes-Farley]

I agree this is a concern, if it turns out that values like 0.1 ppm nitrite are accurate and also not rare events.

 

[Lasse]

Hanna marine nitrite ULR is rather good - I have compared results from it and from some samples send to OCEAMO in Austria. It have shown up that my tank (now 6 years old) have NO2 levels between 0 and 0.11 ppm NO2. The Hanna HC HI764 measure in NO2-N and in µg/L (ppb). The result from this checker has to be multiplied with 3.29 and divided with 1000 in order to get your result in mg/L (ppm)

I´ll think it is important if you are concerned over your nitrate concentration to even measure nitrite with most tests. However - Hanna nitrate LR (0-5 ppm) seems not have as high nitrite interference as the normal colour comparison tests. Test I have done with 1 ppm NO2 standard shows a multiply factor of around 2. It means - if you read 0.5 ppm NO2 - you will have a false reading of NO3 with 1 ppm. This means that if you not are interested to run your tank very low in NO3 (below 0.5 ppm NO3 IMO) the normal NO2 levels (between 0 and 0.1 according to many sources) in aquarium water are of no concern.

For the colour comparison test is normally different - they have between 50 and 100 as an multiply factor - they are many times more sensitive for nitrite interference. I prefer Tropic Marine´s pro NO2/NO3 tests (and Fauna Marines NO2/NO3 test) in these cases because they giove you a possibility to compensate for nitrite interferences.

Sincerely Lasse

 

[Nano sapiens]

Makes me wonder how many reef keepers over the decades have been chasing 'high nitrate', when they actually had low nitrate (with higher than expected nitrite).

Wondering if this could explain some of the deleterious effects reef keepers have seen with more aggressive carbon dosing as the problems might not always be PO4 driven too low, but rather nitrate levels driven too low.

 

[blaxsun]

Tested today and mine came in at 0.2ppm. Seems to be about mid-range.

 

[Hans-Werner]

If you grow Acropora, perhaps you decide to take drastic measures to get the NO3 value down by reducing your feeding and create a major problem.

My recommendation is to widely ignore nitrate and nitrite all together and concentrate on phosphate (hey, wait a moment, of course we want to sell our nitrate tests. ). Ok, test for nitrite and nitrate, but just as information and not to take any serious measures before you are absolutely sure. Why take any measures at all if nothing else is wrong? Like I have learnt in this forum, if it ain't broke, don't fix it!

 

[blaxsun]

My recommendation is to widely ignore nitrate and nitrite all together and concentrate on phosphate (hey, wait a moment, of course we want to sell our nitrate tests. ). Ok, test for nitrite and nitrate, but just as information and not to take any serious measures before you are absolutely sure. Why take any measures at all if nothing else is wrong? Like I have learnt in this forum, if it ain't broke, don't fix it!

My phsophates came in at 0.15ppm tonight - which is higher than normal (usually 0.025-0.050), but I've been feeding a bit more with the introduction of various new fish and corals - and I just replaced the GFO (which was due).

Nitrites were 0.2ppm and nitrates were over 25ppm, so I'm taking steps to hopefully remedy that in the coming days and weeks.

 

[KGV]

Tested today and mine came in at 0.2ppm. Seems to be about mid-range.

FYI. If your tank had zero NO3, because of the 0.2 ppm nitrite, you would read the following ppm NO3.

* Tropic Marin Pro NO3 test: a whopping 20 ppm NO3 (See Topic Marin's conversion table).
* Salifert NO3 test: 5 ppm NO3 (See tests by the guys from Oceamo. Check this thread.
* Hanna LR NO3 test: about 0.4 ppm NO3 (per @Dan_P measurements, confirmed by @Lasse). Check this thread.
* Red Sea Pro NO3 test: about 1.3 ppm NO3 (per @Dan_P measurements). per @Dan_P measurements

So it depends very much on the test. As you can see, it very much depends on the test. Although I have doubts that the TM pro test is so sensitive to nitrites..

 

[blaxsun]

So it depends very much on the test. As you can see, it very much depends on the test. Although I have doubts that the TM pro test is so sensitive to nitrites..

That TM test seems... like a lot. I estimated 2ppm with the nitrite test, so I wasn't that far off with the Red Sea (1.3). I always like to err on the side of caution and give myself some more "wiggle room".

 

[taricha]

Very few measure nitrite once the tank is matured. Perhaps we should? Is my 0.150 ppm nitrite high, indicating a problem with the nitrification cycle? Could high nitrite be typical for tanks with heavy feeding? I grow acros and use heavy in/out, with no supplements but kalk and 2-part.

I've measured NO2 in my system and it's always much lower than 0.1 ppm - more like single digit ppb NO2-N which is within hanna's stated uncertainty (+-10 ppb) of zero. Other people like @Lasse and @Dan_P have measured persistent non-zero NO2 more similar to your finding.

So it's interesting in the respect that it's one way hobby systems can be different without us having a great explanation why.

I've been thinking about the "problem with the nitrification cycle" idea. And it just doesn't seem right to me. Dan has probed the establishment and functioning of nitrifying biofilms, and they are far more resilient than the hobby perception - once they go, it's really hard to stop them. So they are humming along converting NO2->NO3. It's really hard to come up with ways (plausible in an aquarium) to make them stop - and leave behind a tenth or so ppm NO2.
I have a (new to me) hypothesis that systems that have persistent real NO2 values are systems where there is NO3 that is meeting conditions for denitrification. Not halted NO2->NO3 steps, but active functional NO3->NO2 steps (in addition to ammonia->NO2) .

(You can generate this effect by taking tank water, spiking to high NO3, adding vodka and not aerating. You'll measure NO2 produced, and even ammonia being generated.)

If you have NO3 that meets surfaces under low O2 conditions and the surfaces have organic carbon/energy then they are capable. A heavily fed tank with some NO3 seems to check those boxes.

 

[KGV]

I've measured NO2 in my system and it's always much lower than 0.1 ppm - more like single digit ppb NO2-N which is within hanna's stated uncertainty (+-10 ppb) of zero. Other people like @Lasse and @Dan_P have measured persistent non-zero NO2 more similar to your finding.

So it's interesting in the respect that it's one way hobby systems can be different without us having a great explanation why.

I've been thinking about the "problem with the nitrification cycle" idea. And it just doesn't seem right to me. Dan has probed the establishment and functioning of nitrifying biofilms, and they are far more resilient than the hobby perception - once they go, it's really hard to stop them. So they are humming along converting NO2->NO3. It's really hard to come up with ways (plausible in an aquarium) to make them stop - and leave behind a tenth or so ppm NO2.
I have a (new to me) hypothesis that systems that have persistent real NO2 values are systems where there is NO3 that is meeting conditions for denitrification. Not halted NO2->NO3 steps, but active functional NO3->NO2 steps (in addition to ammonia->NO2) .

(You can generate this effect by taking tank water, spiking to high NO3, adding vodka and not aerating. You'll measure NO2 produced, and even ammonia being generated.)

If you have NO3 that meets surfaces under low O2 conditions and the surfaces have organic carbon/energy then they are capable. A heavily fed tank with some NO3 seems to check those boxes.

Interesting, I wasn't aware of such pathways!

 

[Hans-Werner]

I think in saltwater nitrite is not always an intermediary product of nitrification, that accumulates, but maybe even more frequent, a product of incomplete denitrification or maybe better called nitrate respiration.

I think both processes, nitrification and denitrification, frequently stopp in saltwater at the stage of nitrite because of competitive inhibition of the nitrite enzymes by chloride, just like in freshwater chloride and nitrite compete for uptake. Finally ion pumps for uptake are also a kind of enzymes.

So nitrite may also be a result of high nitrate concentration and reductive processes, which cause nitrate respiration (nitrate as a source of oxygen).

One of the (positive) effects of nitrate dosing may be inhibition of Fe(III) reduction (hello @Lasse !). This may cause the observed inhibition of cyanobacterial growth. At least nitrate concentrations higher than 1 ppm do not have any nutrient function in corals but mainly an oxidant function in water.

 

[Lasse]

(hello @Lasse !)

Sincerely Lasse

 

[Lasse]

I have a (new to me) hypothesis that systems that have persistent real NO2 values are systems where there is NO3 that is meeting conditions for denitrification. Not halted NO2->NO3 steps, but active functional NO3->NO2 steps (in addition to ammonia->NO2) .

I think in saltwater nitrite is not always an intermediary product of nitrification, that accumulates, but maybe even more frequent, a product of incomplete denitrification or maybe better called nitrate respiration

Could be that pathway too- but a good nitrification step should take care of nitrite whatever the source is - IMO. If it this way - it may be more important with a good nitrification filter in saltwater compared with freshwater.

Sincerely Lasse

 

[ReefGeezer]

Does the process of converting nitrite to nitrate occur immediately? Could we be measuring a transient level of nitrite that has yet to be converted to nitrate?

 

[taricha]

Interesting, I wasn't aware of such pathways!

yep. @Hans-Werner gives a good explanation with more detail.

Does the process of converting nitrite to nitrate occur immediately? Could we be measuring a transient level of nitrite that has yet to be converted to nitrate?

That is the default assumption.... That NO2 means you are catching N in the act of going from ammonia to NO3. This definitely happens for some number of days during an initial cycle. But it's more of a head-scratcher when you can measure ~0.1ppm NO2 every day in a mature well-lit reef tank.

I'm starting to like the idea more of the importance of the backdoor route from NO3 to NO2. Here's a few reasons to think it might be important.

1) Tanks can have way more NO3 than ammonia circulating in the water. 10ppm NO3 may represent 100x more nitrogen in NO3 than ammonia.
2) There's a lot of competition for the ammonia->NO2 step from photosynthetic organisms. They have lower appetite for NO3.
3) given that saltwater can only hold around 6 or 7mg/L O2, that is going to be easily depleted a short distance below the substrate surface or into biofilms. So if there is 10ppm NO3, then there is going to be plenty of space in a system where NO3 is the best electron acceptor (where O2 is depleted).

 

[Lasse]

But it's more of a head-scratcher when you can measure ~0.1ppm NO2 every day in a mature well-lit reef tank.

May or may not be that way. There is a myth about high nitrification rate in a normal reef tank without any special nitrification filter installed. In freshwater - a biological nitrification filter is in the backbones of the hobby. In high loaded fishfarms I have measured rising nitrite (and ammonia) concentrations during the feeding period (between 08:00 - 20:00) and this in farms with highly developed biofilters. Its a little bit like what´s happens on a highway when a "stau" happens because of roadworks or suddenly rise in traffic. I think Hans Werner understand exactly what I mean

I have always be found of having a small internal foam filter in my sumps but at this moment I do not have it. Never the less - I will do an experiment sooner or later and measure NO2 levels in my reef with or/and without such a simple filter

Sincerely Lasse