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I made these calculations recently for myself, and figured I'd share them with the rest of the forum.

Since the tests for our aquariums just read the total ammonia content in the water, the question has come up how much of that ammonia is actually toxic? This is a complicated question, which really has to do with the ammonia-ammonium equilibrium, ammonia being toxic, ammonium being comparatively much less toxic. Ammonium is not harmless, there is evidence it interferes with the normal salt exchange at the fish gills, but it is not anywhere as dangerous as ammonia.

Also I'd just like to make it clear that any level of ammonia will cause health problems. Ammonia can cause gill damage, that could become permanent, and a very recent article ("Low levels of environmental ammonia increase susceptibility to disease in Chinook salmon smolts " by Ackerman PA, Wicks BJ, Iwama GK, Randall DJ in PHYSIOLOGICAL AND BIOCHEMICAL ZOOLOGY volume 79 JUL-AUG 2006) showed that fish exposed to low levels of ammonia were more susceptible to disease later on in life. But this mini-article is about when emergency action needs to be taken.

The split between the two species (ammonia and ammonium) is determined by equilibrium. The chemistry reaction can be written as:

NH3 + H+ <--> NH4+
(ammonia) + (H+ ions) <--> (ammonium+ ions)

The +'s indicating a charge of +1, and <--> indicating that the reaction can go both ways.

pH is a measure of the concentration of H+ ions. pH really means -log(base 10) of H+. For example, pH of 7.0 means a concentration of 10^-7 H+ ions, a pH of 5.0 means a concentration of 10^-5 H+ ions.

Therefore the lower the pH, the higher the concentration of H+ ions.

Now, with more H+ ions present, the above equilibrium chemical reaction gets pushed towards the right hand side. This is known as Le Chatelier's Principle. But, Le Chatelier's is a general rule, it does not give us the exact splits.

The calculate the splits, we need the equilibrium constant K = [NH3][H+]/[NH4+] where [] stands for the concentration of the species in the []'s. K is a function of temperature, so experimentation needed to be performed, and some high level computations (well beyond the scope of this mini-article) needed to be performed.

Clegg, S. and Whitfield, M did that experiment. (Their paper is "A chemical model of seawater including dissolved ammonia and the stoichiometric dissociation constant of ammonia in estuarine water and seawater from -2 to 40 deg C. Geochimica et Cosmochimia Acta Volume 59, 1995.) They found the equilibrium constant as a function of temperature and salinity.

So with this information, I calculated what % of the total ammonia in the water would be toxic ammonia and ammonium.

How to use the following tables

Know your pH and temperature.
Look up the % toxic ammonia on the following charts for your temp and pH
Know how much ammonia you have in your tank
Multiply your ammonia content by the looked up percentage
If this number is over 0.02 ppm, then action needs to be taken. If this number is over 0.1 ppm, the average fish will be close to death

Example:
I have a tank at 27 deg with pH 6.6 water and 2.0 ppm of ammonia.
% toxic ammonia (from) the chart is: 0.045%

2.0*(0.00045)=0.008 ppm toxic ammonia, so it is not immediately dangerous, though exposure to any ammonia is unhealthy for the fish.

Note that if the pH of that tank was over 8.0, the level of ammonia would require immediate action, so pH does count!

Also, these are only for freshwater, if there is enough demand I might be talked into making up the equivalent charts for saltwater tanks, but not now.

20 deg C or 68.0 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 9.6835
8.8 ... 6.3363
8.6 ... 4.0937
8.4 ... 2.6225
8.2 ... 1.6709
8.0 ... 1.0608
7.8 ... 0.6719
7.6 ... 0.4250
7.4 ... 0.2686
7.2 ... 0.1696
7.0 ... 0.1071
6.8 ... 0.0676
6.6 ... 0.0427
6.4 ... 0.0269
6.2 ... 0.0170
6.0 ... 0.0107
5.0 ... 0.0011
4.0 ... 0.0001


21 deg C or 69.8 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 9.7474
8.8 ... 6.3797
8.6 ... 4.1224
8.4 ... 2.6412
8.2 ... 1.6829
8.0 ... 1.0685
7.8 ... 0.6768
7.6 ... 0.4281
7.4 ... 0.2706
7.2 ... 0.1709
7.0 ... 0.1079
6.8 ... 0.0681
6.6 ... 0.0430
6.4 ... 0.0271
6.2 ... 0.0171
6.0 ... 0.0108
5.0 ... 0.0011
4.0 ... 0.0001


22 deg C or 71.6 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 9.8113
8.8 ... 6.4231
8.6 ... 4.1511
8.4 ... 2.6599
8.2 ... 1.6949
8.0 ... 1.0762
7.8 ... 0.6817
7.6 ... 0.4312
7.4 ... 0.2725
7.2 ... 0.1721
7.0 ... 0.1087
6.8 ... 0.0686
6.6 ... 0.0433
6.4 ... 0.0273
6.2 ... 0.0172
6.0 ... 0.0109
5.0 ... 0.0011
4.0 ... 0.0001


23 deg C or 73.4 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 9.8751
8.8 ... 6.4664
8.6 ... 4.1798
8.4 ... 2.6786
8.2 ... 1.7069
8.0 ... 1.0838
7.8 ... 0.6866
7.6 ... 0.4343
7.4 ... 0.2745
7.2 ... 0.1734
7.0 ... 0.1095
6.8 ... 0.0691
6.6 ... 0.0436
6.4 ... 0.0275
6.2 ... 0.0174
6.0 ... 0.0110
5.0 ... 0.0011
4.0 ... 0.0001


24 deg C or 75.2 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 9.9388
8.8 ... 6.5097
8.6 ... 4.2085
8.4 ... 2.6973
8.2 ... 1.7190
8.0 ... 1.0915
7.8 ... 0.6915
7.6 ... 0.4374
7.4 ... 0.2764
7.2 ... 0.1746
7.0 ... 0.1102
6.8 ... 0.0696
6.6 ... 0.0439
6.4 ... 0.0277
6.2 ... 0.0175
6.0 ... 0.0110
5.0 ... 0.0011
4.0 ... 0.0001



25 deg C or 77.0 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.0025
8.8 ... 6.5530
8.6 ... 4.2372
8.4 ... 2.7159
8.2 ... 1.7310
8.0 ... 1.0992
7.8 ... 0.6964
7.6 ... 0.4405
7.4 ... 0.2784
7.2 ... 0.1758
7.0 ... 0.1110
6.8 ... 0.0701
6.6 ... 0.0442
6.4 ... 0.0279
6.2 ... 0.0176
6.0 ... 0.0111
5.0 ... 0.0011
4.0 ... 0.0001


26 deg C or 78.8 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.0661
8.8 ... 6.5963
8.6 ... 4.2658
8.4 ... 2.7346
8.2 ... 1.7430
8.0 ... 1.1069
7.8 ... 0.7013
7.6 ... 0.4436
7.4 ... 0.2804
7.2 ... 0.1771
7.0 ... 0.1118
6.8 ... 0.0706
6.6 ... 0.0445
6.4 ... 0.0281
6.2 ... 0.0177
6.0 ... 0.0112
5.0 ... 0.0011
4.0 ... 0.0001


27 deg C or 80.6 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.1296
8.8 ... 6.6396
8.6 ... 4.2945
8.4 ... 2.7533
8.2 ... 1.7550
8.0 ... 1.1146
7.8 ... 0.7062
7.6 ... 0.4467
7.4 ... 0.2823
7.2 ... 0.1783
7.0 ... 0.1126
6.8 ... 0.0711
6.6 ... 0.0449
6.4 ... 0.0283
6.2 ... 0.0179
6.0 ... 0.0113
5.0 ... 0.0011
4.0 ... 0.0001


28 deg C or 82.4 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.1931
8.8 ... 6.6828
8.6 ... 4.3232
8.4 ... 2.7720
8.2 ... 1.7671
8.0 ... 1.1223
7.8 ... 0.7110
7.6 ... 0.4498
7.4 ... 0.2843
7.2 ... 0.1796
7.0 ... 0.1134
6.8 ... 0.0716
6.6 ... 0.0452
6.4 ... 0.0285
6.2 ... 0.0180
6.0 ... 0.0113
5.0 ... 0.0011
4.0 ... 0.0001


29 deg C or 84.2 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.2565
8.8 ... 6.7260
8.6 ... 4.3518
8.4 ... 2.7906
8.2 ... 1.7791
8.0 ... 1.1300
7.8 ... 0.7159
7.6 ... 0.4529
7.4 ... 0.2863
7.2 ... 0.1808
7.0 ... 0.1142
6.8 ... 0.0721
6.6 ... 0.0455
6.4 ... 0.0287
6.2 ... 0.0181
6.0 ... 0.0114
5.0 ... 0.0011
4.0 ... 0.0001


30 deg C or 86.0 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.3198
8.8 ... 6.7692
8.6 ... 4.3805
8.4 ... 2.8093
8.2 ... 1.7911
8.0 ... 1.1376
7.8 ... 0.7208
7.6 ... 0.4560
7.4 ... 0.2882
7.2 ... 0.1820
7.0 ... 0.1149
6.8 ... 0.0726
6.6 ... 0.0458
6.4 ... 0.0289
6.2 ... 0.0182
6.0 ... 0.0115
5.0 ... 0.0012
4.0 ... 0.0001


31 deg C or 87.8 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.3831
8.8 ... 6.8123
8.6 ... 4.4091
8.4 ... 2.8280
8.2 ... 1.8032
8.0 ... 1.1453
7.8 ... 0.7257
7.6 ... 0.4591
7.4 ... 0.2902
7.2 ... 0.1833
7.0 ... 0.1157
6.8 ... 0.0730
6.6 ... 0.0461
6.4 ... 0.0291
6.2 ... 0.0184
6.0 ... 0.0116
5.0 ... 0.0012
4.0 ... 0.0001


32 deg C or 89.6 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.4463
8.8 ... 6.8554
8.6 ... 4.4378
8.4 ... 2.8467
8.2 ... 1.8152
8.0 ... 1.1530
7.8 ... 0.7306
7.6 ... 0.4622
7.4 ... 0.2922
7.2 ... 0.1845
7.0 ... 0.1165
6.8 ... 0.0735
6.6 ... 0.0464
6.4 ... 0.0293
6.2 ... 0.0185
6.0 ... 0.0117
5.0 ... 0.0012
4.0 ... 0.0001


33 deg C or 91.4 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.5094
8.8 ... 6.8985
8.6 ... 4.4664
8.4 ... 2.8653
8.2 ... 1.8272
8.0 ... 1.1607
7.8 ... 0.7355
7.6 ... 0.4653
7.4 ... 0.2941
7.2 ... 0.1858
7.0 ... 0.1173
6.8 ... 0.0740
6.6 ... 0.0467
6.4 ... 0.0295
6.2 ... 0.0186
6.0 ... 0.0117
5.0 ... 0.0012
4.0 ... 0.0001


34 deg C or 93.2 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.5724
8.8 ... 6.9416
8.6 ... 4.4950
8.4 ... 2.8840
8.2 ... 1.8392
8.0 ... 1.1684
7.8 ... 0.7404
7.6 ... 0.4684
7.4 ... 0.2961
7.2 ... 0.1870
7.0 ... 0.1181
6.8 ... 0.0745
6.6 ... 0.0470
6.4 ... 0.0297
6.2 ... 0.0187
6.0 ... 0.0118
5.0 ... 0.0012
4.0 ... 0.0001


35 deg C or 95.0 deg F
=============
pH ... % toxic ammonia
=============
9.0 ... 10.6353
8.8 ... 6.9846
8.6 ... 4.5236
8.4 ... 2.9026
8.2 ... 1.8513
8.0 ... 1.1761
7.8 ... 0.7453
7.6 ... 0.4716
7.4 ... 0.2980
7.2 ... 0.1883
7.0 ... 0.1189
6.8 ... 0.0750
6.6 ... 0.0474
6.4 ... 0.0299
6.2 ... 0.0189
6.0 ... 0.0119
5.0 ... 0.0012
4.0 ... 0.0001

This is excellent. The one problem I see is that most people don't have test kits which measure beyond certain increments in the tenth place, so accuracy isn't guaranteed. But that's a fault of commercial equipment providers, not the tables themselves.

One thing I'd like to know is how chemicals which are supposed to bind ammonia (Ammo-Lock, Prime, etc.) affect it chemically. I also wonder if the "harmless" ammonia would still show up on tests.

---

And when he gets to Heaven, to Saint Peter he will tell: "One more Marine reporting, Sir! I've served my time in Hell."

Hi,
Good work. Now, can you edit the thread so that the
findings are beside each other rather than stretching
down the page?
Frank


-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Well, the math doesn't care about the margins of error, though certianly all the measurements will have errors. Without the aid of a computer, no person can accurately tell what shade of color each test is. But, like I said, it doesn't stop the math.

Re: the edit, no, it was a pain in the (you know what) to get the info in there in the first place, that's why the '...'s are inbetween each column in the table entry. If the forum supported HTML's table tags I could, but right now, no.