Aquarium Ammonia Toxicity Calculator
Created by: Ethan Brooks
Last updated:
Calculate the actual toxic ammonia (NH3) concentration in your aquarium based on total ammonia reading, pH, and temperature. Standard test kits measure total ammonia, but toxicity depends heavily on pH - this calculator reveals the true danger level.
Aquarium Ammonia Toxicity Calculator
AquariumCalculate actual toxic ammonia (NH3) from your test kit reading based on pH and temperature
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What is an Ammonia Toxicity Calculator?
An Ammonia Toxicity Calculator determines the actual toxic ammonia (NH3) concentration in your aquarium based on total ammonia reading, pH, and temperature. Standard test kits measure Total Ammonia Nitrogen (TAN), which includes both toxic NH3 and harmless NH4+.
This calculator reveals the true danger level by calculating un-ionized ammonia. The same total ammonia reading can be harmless at low pH or deadly at high pH. Understanding this relationship is crucial for fish health and knowing when emergency action is needed.
Ammonia Toxicity Formulas
Henderson-Hasselbalch Equation:
% NH3 = 100 / (1 + 10^(pKa - pH))
where pKa varies with temperature
Temperature-Adjusted pKa:
pKa = 0.09018 + (2729.92 / (T + 273.15))
where T = temperature in Celsius
Toxic Ammonia:
NH3 (ppm) = Total Ammonia × (% NH3 / 100)
Ammonia Toxicity Levels
Safe: NH3 below 0.02 ppm - No immediate stress, but indicates biological filter issues if detected.
Stressful: NH3 0.02-0.05 ppm - Causes stress, appetite loss, and reduced immunity. Take corrective action.
Dangerous: NH3 0.05-0.2 ppm - Gill damage, labored breathing, lethargy. Emergency water changes needed.
Lethal: NH3 above 0.2 ppm - Causes rapid death. Immediate 50%+ water change required.
Frequently Asked Questions
What is the difference between ammonia and ammonium?
Total Ammonia Nitrogen (TAN) exists in two forms: toxic un-ionized ammonia (NH3) and relatively harmless ionized ammonium (NH4+). The ratio between them depends on pH and temperature. Higher pH and temperature mean more toxic NH3. Test kits measure total ammonia (both forms combined).
What ammonia level is dangerous for fish?
Any detectable un-ionized ammonia (NH3) above 0.02 ppm is stressful. Above 0.05 ppm NH3 causes gill damage and is dangerous. Above 0.2 ppm NH3 is often lethal. Note: these are NH3 values, not total ammonia. At pH 7.0, 0.5 ppm total ammonia equals only 0.003 ppm NH3.
Why does pH affect ammonia toxicity?
pH determines the ammonia/ammonium balance. At pH 7.0, less than 1% of total ammonia is toxic NH3. At pH 8.0, about 8% is NH3. At pH 9.0, about 45% is NH3. This is why the same total ammonia reading is far more dangerous in high-pH tanks like African cichlid or marine aquariums.
How does temperature affect ammonia toxicity?
Higher temperatures increase the percentage of toxic NH3. At pH 8.0, 78°F water has about 5.4% NH3, while 86°F water has about 7.5% NH3. Warmer tanks with the same total ammonia reading have more toxic ammonia present.
What should I do if ammonia is detected?
Immediate actions: 1) Large water change (50%+) with dechlorinated water, 2) Add ammonia-detoxifying product like Seachem Prime, 3) Reduce or stop feeding, 4) Add beneficial bacteria supplement, 5) Test daily and do water changes until ammonia is zero.
Is 0.25 ppm ammonia dangerous?
It depends on pH. At pH 7.0 and 77°F, 0.25 ppm total ammonia contains only 0.0018 ppm toxic NH3 - not immediately lethal but still stressful. At pH 8.2 (marine tank), the same reading means 0.025 ppm NH3 - dangerous with prolonged exposure. Always consider pH.
Why do new tanks have ammonia spikes?
New tanks lack nitrifying bacteria that convert ammonia to nitrite, then nitrate. This 'New Tank Syndrome' causes ammonia spikes during cycling. The nitrogen cycle takes 4-8 weeks to establish. Using seeded media or bacterial supplements can speed this process.
Can ammonia come from sources other than fish?
Yes. Ammonia sources include: decaying food, dead fish or plants, fish waste, decomposing organic matter in substrate, tap water (chloramine releases ammonia when neutralized), and some medications. Overfeeding is a common cause of ammonia problems.
Sources and References
- Emerson, K., et al. "Aqueous Ammonia Equilibrium Calculations", Journal of the Fisheries Research Board of Canada, 1975
- Francis-Floyd, R., "Ammonia", University of Florida IFAS Extension, 2024
- EPA, "Aquatic Life Ambient Water Quality Criteria for Ammonia", 2013