Can Ammonia Oxidizing Bacteria Disappear From An Aquarium?

[Dan_P]

The nitrogen cycle in an aquarium is typically not fully described beyond the obvious telltale signs of ammonia, nitrite and nitrate concentrations. Just recently, nitrate in my aquarium went to zero even though the amount of food added hasn’t changed nor has there been any changes in aquarium maintenance. That got me thinking. Can the ammonia oxidizing organisms quit working, say from an outbreak of a bacteriophage, and then in response, my aquarium switches over from nitrate production to ammonia consumption by the Xenia and algae (macro and micro)?

How could I tell whether the system switched from the typical ammonia-to-nitrate-to-algal-biomass to ammonia-to-algal-biomass?

 

[mcarroll]

I'm not sure about all aspects of your question, but I do think growth (or growth spurts) among tank inhabitants could be a likely explanation for the drop in test numbers.

 

[Randy Holmes-Farley Verified Community Expert]

I think it is all happening all the time, and we have virtually no window into the details of the flux of N.

I cannot see a scenario where AOB disappear entirely since even a phage disaster would only wipe out one species.

 

[Dan_P]

I'm not sure about all aspects of your question, but I do think growth (or growth spurts) among tank inhabitants could be a likely explanation for the drop in test numbers.

I agree, this would be a top candidate explanation, but I am left wondering whether the depletion of nitrate is mainly from ammonia consumption by the growth spurt rather than nitrate consumption. And is there a simple experiment to sort this out?

 

[Dan_P]

I think it is all happening all the time, and we have virtually no window into the details of the flux of N.

I cannot see a scenario where AOB disappear entirely since even a phage disaster would only wipe out one species.

Is a reasonable model “food enters aquarium, fish consumes food and excretes a high percent of the food nitrogen as ammonia over some hours, resulting in the water containing a low level of nitrogen for many hours per day”? This model shares the ammonia across all organisms while it is converted to nitrate.

 

[Randy Holmes-Farley Verified Community Expert]

Is a reasonable model “food enters aquarium, fish consumes food and excretes a high percent of the food nitrogen as ammonia over some hours, resulting in the water containing a low level of nitrogen for many hours per day”? This model shares the ammonia across all organisms while it is converted to nitrate.

That sounds logical to me. It’s likely a bit more complicated since each organism type will have different rates of uptake at different concentrations. Fake numbers, but some may stop taking up ammonia when it drops below 0.01 ppm and some may be able to keep going at even lower levels.

 

[mcarroll]

I agree, this would be a top candidate explanation, but I am left wondering whether the depletion of nitrate is mainly from ammonia consumption by the growth spurt rather than nitrate consumption. And is there a simple experiment to sort this out?

High-accuracy N-testing would help, but some (most?) of these nutrient cycles happen very locally.... Hm.

This uncertainty is literally why I (we?) like to run a surplus of NO3...just because it seems to indicate the N-system is "replete".

 

[jeremie]

The requirement for certain trace elements, such as iron and molybdenum, might be higher in a system that utilizes more nitrate, since nitrate reductase needs them to function. Although I’m not sure whether the difference would be large enough to be detected by ICP. This study did show that the requirement for iron is higher when zooxanthellae use nitrate as a nitrogen source compared to when they use ammonia.

It might be worth trying to dose some nitrate and then switch to ammonia, or vice versa, to see whether the organisms respond differently. I do recall that when I first switched from dosing nitrate to dosing ammonia in my tanks, I could see noticeably faster growth in some of my Acropora within two weeks, even though the amount of nitrogen added was the same.

 

[Randy Holmes-Farley Verified Community Expert]

The requirement for certain trace elements, such as iron and molybdenum, might be higher in a system that utilizes more nitrate, since nitrate reductase needs them to function. Although I’m not sure whether the difference would be large enough to be detected by ICP. This study did show that the requirement for iron is higher when zooxanthellae use nitrate as a nitrogen source compared to when they use ammonia.

It might be worth trying to dose some nitrate and then switch to ammonia, or vice versa, to see whether the organisms respond differently. I do recall that when I first switched from dosing nitrate to dosing ammonia in my tanks, I could see noticeably faster growth in some of my Acropora within two weeks, even though the amount of nitrogen added was the same.

Complicating that fact is something Hans-Werner pointed out: a lot of the demand for iron may involve abiotic precipitation.

 

[Dan_P]

That sounds logical to me. It’s likely a bit more complicated since each organism type will have different rates of uptake at different concentrations. Fake numbers, but some may stop taking up ammonia when it drops below 0.01 ppm and some may be able to keep going at even lower levels.

Thanks for this. I can conjecture now on solid ground :-)

Important point you make about ammonia uptake. Something that wasn’t in mind.

 

[Dan_P]

High-accuracy N-testing would help, but some (most?) of these nutrient cycles happen very locally.... Hm.

This uncertainty is literally why I (we?) like to run a surplus of NO3...just because it seems to indicate the N-system is "replete".

Thanks for reminding me about local nutrient (nitrogen here) cycles. I think it’s a good time to survey the ammonia content of substrate pore water.

 

[Dan_P]

The requirement for certain trace elements, such as iron and molybdenum, might be higher in a system that utilizes more nitrate, since nitrate reductase needs them to function. Although I’m not sure whether the difference would be large enough to be detected by ICP. This study did show that the requirement for iron is higher when zooxanthellae use nitrate as a nitrogen source compared to when they use ammonia.

It might be worth trying to dose some nitrate and then switch to ammonia, or vice versa, to see whether the organisms respond differently. I do recall that when I first switched from dosing nitrate to dosing ammonia in my tanks, I could see noticeably faster growth in some of my Acropora within two weeks, even though the amount of nitrogen added was the same.

The iron connection is worth thinking about. I dose ChaetoGro and Flourish iron in hopes to keep sufficient iron available.