Ammonia - TAN / UIA online calculator

[Jay Hemdal Verified Community Expert]

I found what looks like a very easy to use, comprehensive online calculator for assessing ammonia toxicity in aquariums. It takes into account the salinity, water temperature and pH to determine the level of un-ionized ammonia (UAI) for a given amount of Total Ammonia - Nitrogen.

The risk assessment it provides is based on zebrafish data. Empirically, I've found that many species of marine fish have similar sensitivity to UAI. I ran a number of scenarios and the calculator seems very robust to me. The only caveat is that you need to be sure you enter the salinity (in ppt) below the "Include salinity correction" radio button when it is selected.

https://conductscience.com/tools/unionized-ammonia-calculator#tool-calculator

 

[overhead]

Does the Hanna ammonia test report TAN? If I use the conversion equation included in their instructions it reports .005 unionized ammonia. If I use this calculator it reports .06. I assume it is a data entry issue on my part. Much like my mistake in saying "unionized" instead of "un-ionized".

 

[Jay Hemdal Verified Community Expert]

Does the Hanna ammonia test report TAN? If I use the conversion equation included in their instructions it reports .005 unionized ammonia. If I use this calculator it reports .06. I assume it is a data entry issue on my part. Much like my mistake in saying "unionized" instead of "un-ionized".

The Hanna checker reports as "TAN". Here is a thread from a few years ago with a review of it:

https://www.reef2reef.com/threads/a...ecker-hi784-chemistry-and-performance.933667/

 

[overhead]

The Hanna checker reports as "TAN". Here is a thread from a few years ago with a review of it:

https://www.reef2reef.com/threads/a...ecker-hi784-chemistry-and-performance.933667/

Thanks. It is likely my mistake. Next time I check ammonia I will run the numbers again.

 

[Randy Holmes-Farley Verified Community Expert]

I have to say I strongly disagree with using this calculator for marine fish.

The calculations may be ok, but the conclusions are NOT supported by any published tox data for marine fish.

Unless someone shows that 1.5 ppm TAN kills marine fish, I wholeheartedly say: Do NOT use this to assess tox.

Actual published data for many species always (as far as I have seen) is higher than 10 ppm to kill.

 

[Jay Hemdal Verified Community Expert]

I have to say I strongly disagree with using this calculator for marine fish.

The calculations may be ok, but the conclusions are NOT supported by any published tox data for marine fish.

Unless someone shows that 1.5 ppm TAN kills marine fish, I wholeheartedly say: Do NOT use this to assess tox.

Actual published data for many species always (as far as I have seen) is higher than 10 ppm to kill.

I understand that you have papers to support that, but in response, I recently polled a public aquarium list serve and none of them offered any support for the idea that it takes ~ 10 ppm TAN to kill marine fish.

I'm going to stick with the public aquarium "best practice" which is that (in most cases), a TAN reading of > 0.50 ppm is the "action level" where the issue needs to be addressed. This works out to be a UIA of around 0.08 ppm for most home marine aquariums). This aligns with Noga, Francis-Floyd, and Hadfield et-al (the latter actually uses a UIA action level of <0.02).

Empirically, I KNOW that a TAN of >1.0 will harm many species of marine fish (unless the pH is depressed). Besides, I'm only interested in the 168 hour LC zero value, not the 96 hour LC50.....

 

[commod0re]

Is this even accurate? It doesn’t match the output of this calculator on Hamzas Reef which I have used and verified with a seneye

https://hamzasreef.com/Contents/Calculators/FreeAmmonia.php
According to the Hamza’s Reef calculator, TAN 0.5 at 8.1 pH, 35 PPT salinity, and 77F (25C) temperature, puts the free ammonia level at 0.0281 ppm. Putting the same figures into this new calculator puts it at 0.05

That’s quite a discrepancy (77%)

 

[Randy Holmes-Farley Verified Community Expert]

I understand that you have papers to support that, but in response, I recently polled a public aquarium list serve and none of them offered any support for the idea that it takes ~ 10 ppm TAN to kill marine fish.

I'm going to stick with the public aquarium "best practice" which is that (in most cases), a TAN reading of > 0.50 ppm is the "action level" where the issue needs to be addressed. This works out to be a UIA of around 0.08 ppm for most home marine aquariums). This aligns with Noga, Francis-Floyd, and Hadfield et-al (the latter actually uses a UIA action level of <0.02).

Empirically, I KNOW that a TAN of >1.0 will harm many species of marine fish (unless the pH is depressed). Besides, I'm only interested in the 168 hour LC zero value, not the 96 hour LC50.....

The calculator literally says 1.5 ppm TAN is lethal. That may be true of some fish, but not any of the marine fish that I could find actual data for, including clownfish.

We can certainly disagree, especially in what levels might be stressful or cause sub-lethal effects.

I gave my comments and you gave yours, and folks can decide for themselves what to make of the divergence.

That said, there are very few situations except cycling and shipping where the difference even matters in a reef tank since ammonia rarely rises to substantial levels by either of our criteria.

My personal opinion is that many hobbyists have an inaccurate opinion on the toxicity of ammonia, partly driven by companies that push products to “treat” for ammonia when such a treatment is neither effective nor necessary. But when their fish survives 1 or 2 ppm TAN, they falsely conclude the product works, tell their buddies, and the cycle repeats over and over.

 

[Randy Holmes-Farley Verified Community Expert]

For those interested in digging deeper, I discuss fish ammonia tox data here:

https://www.reef2reef.com/ams/ammonia-is-our-friend.1062/

 

[commod0re]

More importantly than that though: I’m not convinced this is even an accurate calculation of free ammonia

 

[Jay Hemdal Verified Community Expert]

More importantly than that though: I’m not convinced this is even an accurate calculation of free ammonia

I did some spot checks against the table in Hadfield et-al (a new book on fish health) and it lined up pretty well. Both use Emerson 1975 as their source. If Hamzas used a different source, that would explain the discrepancy...do they give their source? I didn't see a reference....

 

[Privateye]

I can't speak as to the saltwater correction, but the calculations match the excel sheet I've used for freshwater for over a decade. I tried playing with a variety of values. I feel comfortable with the calculations for freshwater.

As for the interpretations, I kind of agree with both Randy and Jay in a way. Toxicity can be highly species-dependent, yet in this industry general guidelines are often sought, and often helpful to those with less experience. Even just introducing the concept to people is helpful, so I welcome the post.

I'd be worried about UIA at lower levels when dealing with discus than I would be for sturgeon or tilapia, for instance. Life stage of course makes a huge difference too - I think we can agree that larvae can be more-sensitive than juvenile or adult fish.

What I find interesting is that when the calculator shows less-worrisome outputs, they mention the species of concern: zebrafish. I think this calculator wasn't intended for marine fishes, but for the tons of zebrafish systems used for biomedical research around the world. So think of it as a tool for an MD/PhD who knows biology well, but not fish. At least that characterizes most of the zebrafish people I've spoken to.

 

[christinna77]

I actually built my own tool here: https://tools.tilefi.sh/#/free-ammonia and it matches Hamzas.

My source was the Purdue derivation https://web.archive.org/web/2005031...piwc/w3-research/free-ammonia/derivation.html with the USEPA 1989 saltwater correction.

The other calculator is giving a pKa of 9.055 at 25C at 35 ppt, but Emerson's freshwater pKa at 25C is 9.246. If I understand it correctly, saltwater should push pKa higher, not lower. So I think their salinity correction is going the wrong direction.

For example, with no salinity correction at all, 0.5 TAN at pH 8.1 and 25C, this tool reports 0.0333 ppm free ammonia, and mine reports 0.0337, so that mostly matches. But with salt correction at 35 ppt, this tool reports 0.0500 ppm free ammonia, while mine reports 0.0281. And if you keep increasing the salinity, the free ammonia also goes up, while it should go down.

 

[Randy Holmes-Farley Verified Community Expert]

I actually built my own tool here: https://tools.tilefi.sh/#/free-ammonia and it matches Hamzas.

My source was the Purdue derivation https://web.archive.org/web/2005031...piwc/w3-research/free-ammonia/derivation.html with the USEPA 1989 saltwater correction.

The other calculator is giving a pKa of 9.055 at 25C at 35 ppt, but Emerson's freshwater pKa at 25C is 9.246. If I understand it correctly, saltwater should push pKa higher, not lower. So I think their salinity correction is going the wrong direction.

For example, with no salinity correction at all, 0.5 TAN at pH 8.1 and 25C, this tool reports 0.0333 ppm free ammonia, and mine reports 0.0337, so that mostly matches. But with salt correction at 35 ppt, this tool reports 0.0500 ppm free ammonia, while mine reports 0.0281. And if you keep increasing the salinity, the free ammonia also goes up, while it should go down.

Seawater generally stabilizes the more highly charged forms in acid base reactions. Hence it is easier to form
PO4- - - in seawater than in fresh.

For ammonia, that would be NH4+ and this makes more NH4+ at a given pH, which I agree should raise the pKa.

Weirdly, the google search AI gets this exactly backwards and cites a reference showing it got it backwards. lol

There are numerous complexities to this question, but Figure 1 in this reference clearly shows a higher pKa in seawater.

https://connectsci.au/en/article/4/3/183/23841/Ammonia-ammonium-dissociation-coefficient-in

 

[commod0re]

I did some spot checks against the table in Hadfield et-al (a new book on fish health) and it lined up pretty well. Both use Emerson 1975 as their source. If Hamzas used a different source, that would explain the discrepancy...do they give their source? I didn't see a reference....

It’s entirely possible that the hamza’s reef calculator is the wrong one, it seems to align with what I am able to measure myself but that doesn’t mean much since it’s not easy to validate how accurate my own measurements even are. I think there’s a vague reference to a source at the top of the page but I wasn’t able to use that information to find the alluded source

Edit: oh it’s the salinity correction that’s applied wrong, interesting! This gives me back some confidence in the hamza’s reef calculator

 

[Dan_P]

I have to say I strongly disagree with using this calculator for marine fish.

The calculations may be ok, but the conclusions are NOT supported by any published tox data for marine fish.

Unless someone shows that 1.5 ppm TAN kills marine fish, I wholeheartedly say: Do NOT use this to assess tox.

Actual published data for many species always (as far as I have seen) is higher than 10 ppm to kill.

What is the real harm in over estimating the risk of ammonia toxicity? Lethality?

 

[Randy Holmes-Farley Verified Community Expert]

What is the real harm in over estimating the risk of ammonia toxicity? Lethality?

Wasted time and money. Buying Prime. Changing water. Waiting endlessly for the 0.2 ppm on the test kit to go to zero, etc.

Overestimating is better than underestimating, however.

 

[Dan_P]

Wasted time and money. Buying Prime. Changing water. Waiting endlessly for the 0.2 ppm on the test kit to go to zero, etc.

Overestimating is better than underestimating, however.

Yes, at the low end of the spectrum there seems to be much angst.

How about the difference of opinion that 1.5 vs >10 ppm TAN is lethal? Is the time and money waste as clear cut?

 

[Randy Holmes-Farley Verified Community Expert]

Yes, at the low end of the spectrum there seems to be much angst.

How about the difference of opinion that 1.5 vs >10 ppm TAN is lethal? Is the time and money waste as clear cut?

I don’t know, but I think it’s hard to support inaccurate information.

I don’t ever want big brother providing inaccurate info to get me to do or not do something.

 

[Dan_P]

I don’t know, but I think it’s hard to support inaccurate information.

I don’t ever want big brother providing inaccurate info to get me to do or not do something.

Fair enough.