How Dangerous Is Ammonia?

I'm a bit confused about some of the advice being given in regards to ammonia in freshwater tanks. Let's agree right up front that the best ammonia is no ammonia, but that's not possible if you're going to keep livestock that get fed and eliminate waste.

So now the question is, what level of ammonia is significantly detrimental to the livestock? The common test kits, certainly the one I have, measure the total of NH3, free ammonia, and NH4, ammonium. It doesn't differentiate between the two, providing just the total of both. From what I've read, it's the free ammonia that's the problem. Ammonium is essentially harmless according to my reading.

Now let's bring pH into the picture. At typical aquarium temperatures, in a tank with a pH of 8.0, less than 10% of the total ammonia is free ammonia. Over 90% of it is harmless ammonium. As pH drops, even less is free ammonia. At a pH of 7.0 the free ammonia comprises less than 1% of the total ammonia. So at a pH of 7.0, that reading of 1.0ppm total ammonia means you have less than 0.01ppm free ammonia that will harm your fish.

This leads to a number of questions. First, what level of free ammonia poses a true risk to the livestock? Obviously some are more sensitive than others, but just ballpark here. Is 0.01ppm free ammonia really so dangerous to fish as to justify the level of panic that seems to ensue when total ammonia is 1ppm? Or is there a general lack of understanding about the interaction of ammonia and pH? Is some of this panic spilling over from the world of saltwater where the typically higher pH does make ammonia a much more serious problem?

I'm seeing posts from people who seem to be dosing their tanks with this, that, and the next thing all because they're getting a slightly elevated total ammonia reading. From what I can tell, most of the concoctions they're dumping into their tanks are only doing what a fairly normal freshwater pH has most likely already done. I see reports of total ammonia not dropping as a result of adding these potions, so they clearly aren't magically making the ammonia disappear. If total ammonia doesn't drop after adding these products, then all they can possibly be doing is binding an extra hydrogen to the free ammonia and converting it to ammonium. This would certainly be beneficial if they can do it at the higher pH levels where it doesn't happen as a normal function of water chemistry, but at a pH of 7.0 this has already mostly happened, so addition of the product to the aquarium would seem pointless.

If I'm way off base here, please let me know where I've gone wrong.

 

It is safe to assume that any measurable ammonia in an aquarium is potentially toxic to fish unless the pH is below 7. Even then, an ammonia level that tests above 1.0 ppm with the testing equipment commercially available to amature aquarists today, must be considered potentially harmful over time.
A well cycled, appropriately stocked, well maintained aquarium will have an adequate amount of ammonia oxidizing bacteria to prevent the accumulation of any measurable NH3/NH4 with said testing equipment.

 

i'll have to research that, b/c I thought above 7 ph it was all ammonia, and below 7 ph it starts becoming ammonium, and the more acidic, more of it becomes ammonium, and below 6 pH when it all becomes ammonium.

most of the test kits we use are fairly inexpensive $20-25. there are more expensive kits that can differentiate between ammonia and ammonium. I remember one or two of our members have such testing kits. but generally if your tank is cycled and there is enough bio media to hold enough nitrifying bacteria it won't be a problem.

previous discussion: https://www.fishlore.com/aquariumfi...onship-when-does-ammonia-become-toxic.196863/

this one has a chart http://www.aztic.org/wp-content/upl...re-on-Ammonia-pH-Water-Temperature-v-2017.pdf

 

i'll have to research that, b/c I thought above 7 ph it was all ammonia, and below 7 ph it starts becoming ammonium, and the more acidic, more of it becomes ammonium, and below 6 pH when it all becomes ammonium.

Here is the chart I used. At a temperature of 28C and a pH of 8.2, 10% of the total ammonia nitrate (TAN) is free ammonia. As pH drops the percent of free ammonia does as well. At a pH of 7.2 only 1% of TAN is free ammonia. The chart doesn't go below pH 7.0, but it's clear that at that pH you'd need very significant amounts of TAN to have enough free ammonia for it to be an issue.

this one has a chart http://www.aztic.org/wp-content/upl...re-on-Ammonia-pH-Water-Temperature-v-2017.pdf

Thanks for this link. Putting this together with the other chart I linked suggests free ammonia starts to become a problem at 0.02ppm. (That's of just free ammonia, not TAN.) I checked the numbers at several spots and they all were within small rounding errors of 0.02.

It seems clear from the article you linked that before dumping half a bottle of Prime into your tank you should check the pH to see if your 0.50ppm TAN reading actually justifies it. OTOH, if your pH typically hovers around 8.0, you need to react to any indication of ammonia.

 

Ammonium is weak conjugate acid of ammonia, where it's the presence of the H+ ion that causes the change between the two.

Therefore, in an acidic tank, it's likely that ammonium will result. Of course, if you continue to add more ammonia, regardless of pH, eventually all avaliable H+ ions will be reaction with ammonia to produce ammonium, which then at equilibrium, will result in only ammonia being produced. Think of it like adding salt to water, at first it may all dissolve, but after a while, salt will be unable to dissolve due to reacting the 'maximum concentration'. Of course, heat the water (or for ammonia, increase acidity of water, more ammonium is converted) you may be able to have a higher concentration of salt.