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The classic idea of nitrification is that ammonia is oxidized to nitrite and nitrate by bacteria in surfaces like sand, rock, and filters. But ammonia is also the preferred N source for photosynthetic organisms. Everything from coral to single cell algae. Additionally, heterotrophic bacteria can use whatever organic carbon sources are available to consume ammonia as well. So Just because ammonia disappears doesn't mean that it went through the ammonia -> NO2 -> NO3 "cycle", it might've just been consumed and become biomass instead.
There's a somewhat contrarian theory that in some tanks, ammonia mostly goes to algae and coral and very little gets nitrified at all.
See this article for that idea: #1 WHAT IF I TOLD YOU... Ammonia is causing your algae problems?
Also AquaBiomics finds some systems that have lots of nitrifiers and some that have barely any Ammonia Oxidizing Bacteria (AOB) and undetectably low Nitrite Oxidizing Bacteria (NOB). Article: The Microbial Community in a Professional Coral Aquaculture System
Anyway: Some things made me think I have a system that would fit this - processing ammonia in non "cycling" ways, so I went looking for data to measure my ammonia eaters. This answered a lot of Q's for me and raised a few more.
As a baseline comparison, here's the tank response to a one-time dose of ammonia during the day period, just a few measurement to get the general size and scale of the rates my system processes ammonia. (pH was 8.0 - this level of ammonia is well below EPA 1-hr level of 2.9 TAN @ pH 8)
The tank consumed ammonia at 0.161ppm/hr Total Ammonia Nitrogen (TAN). This works out to 3.9ppm/day.
So how much of this actually happens in the sand?
I dosed tank water to just under 0.5ppm TAN and split it into 100mL samples. Four samples got a series of different amounts of sand 0%,1%, 2% or 5% (a.k.a. 1, 2, or 5mL in 100mL sample) of white sand from the top of the sandbed where water flows across it pretty well.
Two other samples got1% sand + newly opened bottled starter products:
1% sand + BioSpira (recommended minimum dose)
1% sand + One and Only (5x recommended minimum dose)
They were placed in the dark on an orbital shaker at 70 rpm to keep the water moving and tested over 2.5 days.
The series of samples with varying amounts of sand are in shades of blue, the 1% sand + biospira (red) acted more like the 5% sand. The 1% sand + One and Only (green) acted basically like just 1% sand. The trendlines were used to estimate the consumption rates.
Surprisingly, even no sand at all - just 100mL of water clearly consumed ammonia. [not repeatable: see post 48 update]
Here's visualizing the rate of ammonia consumption (slopes from previous graph) vs the amount of sand there was.
There is probably diminishing returns for higher levels of sand since at 5% the sand is piling up and a smaller portion is in contact with the moving water. BioSpira +1% sand clearly effective above what the 1% sand in the sample could do, while One and Only had no detectable effect. What proportion of sand is most applicable to my tank? My tank water is 40cm deep, and likely only the top 1cm of sand (or less) is reasonably in contact with moving water above, so 2% or less seems a good ballpark approximation to how my sandbed behaves.
I therefore estimate my tank sand can eat somewhere in the range of 0.10 to 0.15ppm/day TAN, or only <4% of my overall system consumption of 3.9ppm/day, meaning only 4% of that maximum daily ammonia consumption could be done in the sand+water.
Speaking of water, this graph makes it really clear that my tank water processes ammonia. In the 1% sand samples, the water may be doing half the work. Crazy! (Ammonia Oxidizing Archaea??)
[edit: Not repeatable. See post 48 for better data]
Okay one last thing. I haven't actually shown this ammonia was oxidized to nitrite/nitrate. It might have just been consumed by heterotrophs or algae in the sand. So let's look for NO2 / NO3.
Nitrite is not worth plotting a graph: Biospira produced 0.35ppm NO2, all other samples produced zero NO2. So maybe it was oxidized to NO3.
So lets take a look at NO3.
Wow that looks a lot like the Ammonia consumption data in the previous graph (except there's more NO3 than expected in the One and Only). So let's see how tightly they match up. (The NO3 measurement in Biospira sample was corrected for the Nitrite interference using @Dan_P work here)
This plot compares the amount of Total Ammonia - Nitrogen consumed over the 2.5 days (on the left) to the NO2 + NO3 - nitrogen accumulated at the end (on the right)
First, the sand-only samples (in blue) match up very well. Secondly, the bottle products (solid red and green lines) showed way too much NO3 for the amount of Ammonia they consumed, so I checked for NO3 in the bottles - they are nitrifiers after all. Indeed, recommended min dose of Biospira adds 2.8ppm NO3, and 5x Rec'd min dose of O&O adds 2.3ppm NO3. After correcting for the NO3 that came in the bottles, the ammonia consumption and NO2 & NO3 production line up very well (red and green dashed lines). So clearly the ammonia consumption that happens in the sand and water really is nitrification, oh, and the bottle of O&O really was dead - guess it got frozen at some point. (BTW the slight increase from ammonia-N consumption to NO3-N production in these samples is probably from some organics in the sand being remineralized during the 2.5 day experiment. Note the effect increases with increasing sand level.)
So here's the takeaway.
I can measure the consumption of ammonia by my sand (and water!) and show that it's nitrification. And it's really small - maybe only 4% of the rate of the ammonia consumption in my system overall. The bulk of ammonia in my system is probably eaten by algae and coral.
I think my tank may be an extreme case. My 70 gal system has probably a kg of mixed coral and several hundred grams of algae, algae grows and exports quickly. It's had a history of sometimes large carbon dosing, but nothing in the past few months. Either my tank or my sump is always lighted. The rates of ammonia consumption capable by coral and algae when lighted is huge. So it makes sense that nitrification looks like a bit player in my system, my tank always runs zero detectable NO3, and any that is dosed disappears quickly. I plan to send a sample to Aquabiomics tomorrow to see if the genetic approach tells the same story.
But I don't think I have the only tank like this! I think the hobby might have quite a few systems where the traditional nitrogen cycle is essentially a non-factor. Is this good? Bad? I don't know. But it's clear from the effect of biospira, that this would be easy to change if someone wanted to.
- My system is capable of removing ammonia quickly: ~4ppm/day total ammonia-Nitrogen (TAN)
- The sand processes ammonia slowly: ~0.1-0.2ppm/day TAN meaning the other 95+% happens somewhere else
The tank water itself also has detectable ammonia processing: ~0.05ppm/day TAN[Tank water itself not doing anything: see update in post 48]- In the sand and the water, the processing is provably Nitrification
- A Recommended Minimum Dose of Biospira consumes ammonia faster straight out of the bottle than my 10 year old sand
- I don't know if this is good or bad
The classic idea of nitrification is that ammonia is oxidized to nitrite and nitrate by bacteria in surfaces like sand, rock, and filters. But ammonia is also the preferred N source for photosynthetic organisms. Everything from coral to single cell algae. Additionally, heterotrophic bacteria can use whatever organic carbon sources are available to consume ammonia as well. So Just because ammonia disappears doesn't mean that it went through the ammonia -> NO2 -> NO3 "cycle", it might've just been consumed and become biomass instead.
There's a somewhat contrarian theory that in some tanks, ammonia mostly goes to algae and coral and very little gets nitrified at all.
See this article for that idea: #1 WHAT IF I TOLD YOU... Ammonia is causing your algae problems?
Also AquaBiomics finds some systems that have lots of nitrifiers and some that have barely any Ammonia Oxidizing Bacteria (AOB) and undetectably low Nitrite Oxidizing Bacteria (NOB). Article: The Microbial Community in a Professional Coral Aquaculture System
As I review these surveys from different tanks, lately I’ve been thinking about competition between microbes and other organisms for ammonia. I’m considering the hypothesis that some tanks process most of the ammonia through nitrification, some through assimilation by invertebrates or heterotrophic bacteria, and some through assimilation by algae.
Anyway: Some things made me think I have a system that would fit this - processing ammonia in non "cycling" ways, so I went looking for data to measure my ammonia eaters. This answered a lot of Q's for me and raised a few more.
As a baseline comparison, here's the tank response to a one-time dose of ammonia during the day period, just a few measurement to get the general size and scale of the rates my system processes ammonia. (pH was 8.0 - this level of ammonia is well below EPA 1-hr level of 2.9 TAN @ pH 8)
The tank consumed ammonia at 0.161ppm/hr Total Ammonia Nitrogen (TAN). This works out to 3.9ppm/day.
So how much of this actually happens in the sand?
I dosed tank water to just under 0.5ppm TAN and split it into 100mL samples. Four samples got a series of different amounts of sand 0%,1%, 2% or 5% (a.k.a. 1, 2, or 5mL in 100mL sample) of white sand from the top of the sandbed where water flows across it pretty well.
Two other samples got1% sand + newly opened bottled starter products:
1% sand + BioSpira (recommended minimum dose)
1% sand + One and Only (5x recommended minimum dose)
They were placed in the dark on an orbital shaker at 70 rpm to keep the water moving and tested over 2.5 days.
The series of samples with varying amounts of sand are in shades of blue, the 1% sand + biospira (red) acted more like the 5% sand. The 1% sand + One and Only (green) acted basically like just 1% sand. The trendlines were used to estimate the consumption rates.
Here's visualizing the rate of ammonia consumption (slopes from previous graph) vs the amount of sand there was.
There is probably diminishing returns for higher levels of sand since at 5% the sand is piling up and a smaller portion is in contact with the moving water. BioSpira +1% sand clearly effective above what the 1% sand in the sample could do, while One and Only had no detectable effect. What proportion of sand is most applicable to my tank? My tank water is 40cm deep, and likely only the top 1cm of sand (or less) is reasonably in contact with moving water above, so 2% or less seems a good ballpark approximation to how my sandbed behaves.
I therefore estimate my tank sand can eat somewhere in the range of 0.10 to 0.15ppm/day TAN, or only <4% of my overall system consumption of 3.9ppm/day, meaning only 4% of that maximum daily ammonia consumption could be done in the sand+water.
[edit: Not repeatable. See post 48 for better data]
Okay one last thing. I haven't actually shown this ammonia was oxidized to nitrite/nitrate. It might have just been consumed by heterotrophs or algae in the sand. So let's look for NO2 / NO3.
Nitrite is not worth plotting a graph: Biospira produced 0.35ppm NO2, all other samples produced zero NO2. So maybe it was oxidized to NO3.
So lets take a look at NO3.
Wow that looks a lot like the Ammonia consumption data in the previous graph (except there's more NO3 than expected in the One and Only). So let's see how tightly they match up. (The NO3 measurement in Biospira sample was corrected for the Nitrite interference using @Dan_P work here)
This plot compares the amount of Total Ammonia - Nitrogen consumed over the 2.5 days (on the left) to the NO2 + NO3 - nitrogen accumulated at the end (on the right)
First, the sand-only samples (in blue) match up very well. Secondly, the bottle products (solid red and green lines) showed way too much NO3 for the amount of Ammonia they consumed, so I checked for NO3 in the bottles - they are nitrifiers after all. Indeed, recommended min dose of Biospira adds 2.8ppm NO3, and 5x Rec'd min dose of O&O adds 2.3ppm NO3. After correcting for the NO3 that came in the bottles, the ammonia consumption and NO2 & NO3 production line up very well (red and green dashed lines). So clearly the ammonia consumption that happens in the sand and water really is nitrification, oh, and the bottle of O&O really was dead - guess it got frozen at some point. (BTW the slight increase from ammonia-N consumption to NO3-N production in these samples is probably from some organics in the sand being remineralized during the 2.5 day experiment. Note the effect increases with increasing sand level.)
So here's the takeaway.
I can measure the consumption of ammonia by my sand (
I think my tank may be an extreme case. My 70 gal system has probably a kg of mixed coral and several hundred grams of algae, algae grows and exports quickly. It's had a history of sometimes large carbon dosing, but nothing in the past few months. Either my tank or my sump is always lighted. The rates of ammonia consumption capable by coral and algae when lighted is huge. So it makes sense that nitrification looks like a bit player in my system, my tank always runs zero detectable NO3, and any that is dosed disappears quickly. I plan to send a sample to Aquabiomics tomorrow to see if the genetic approach tells the same story.
But I don't think I have the only tank like this! I think the hobby might have quite a few systems where the traditional nitrogen cycle is essentially a non-factor. Is this good? Bad? I don't know. But it's clear from the effect of biospira, that this would be easy to change if someone wanted to.
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