7.  Does temperature and pH effect ammonia?

Ammonia varies in toxicity at different pH and temperature of the water. For example, ammonia (NH3) continually changes to ammonium (NH4+) and vice versa, with the relative concentrations of each depending on the water's temperature and pH. Ammonia is extremely toxic; ammonium is relatively harmless. At higher temperatures and higher pH, more of the nitrogen is in the toxic ammonia form than at lower pH.

Standard test kits measure total ammonia (ammonia plus ammonium) without distinguishing between the two forms. The following chart gives the maximum long-term level of ammonia-N in mg/L (ppm) that can be considered safe at a given temperature and pH. Again, note that a tank with an established biological filter will have no detectable ammonia; this chart is provided only for emergency purposes. If your levels approach or exceed the levels shown, take emergency action IMMEDIATELY.

Percent of ammonia from 'total ammonia'
Temp C°/0° pH 6.5 pH 7.0 pH 7.5 pH 8.0 pH 8.5
20°C (68°F) 0.13 0.40 1.24 8.82 11.2
25°C (77°F) 0.18 0.57 1.77 5.38 15.3
28°C (82°F) 0.22 0.70 2.17 6.56 18.2
30°C (86°F) 0.26 0.80 2.48 7.46 20.3
Generally, any value above 0.5 is dangerous

Independent Studies

California State, Texas A&M Corpus Christi, University of Nevada Las Vegas


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