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Pool · Planning aid

Aquarium Ammonia Calculator

Estimate free ammonia from total ammonia, pH, and temperature with a conservative toxicity warning.

Planning aidSafety-sensitiveVisible assumptions
Updated 2026-06-24
Calculation method AQUARIUM_AMMONIA-1.0
Page type Planning aid
Tool type Safety-sensitive
Planning aid

This calculator is available as a planning aid with examples, FAQs, and visible assumptions.

Safety-sensitive planning aid. Product labels, local rules, codes, and qualified professional guidance override this calculator.

Estimate water adjustment from test readings

This pool/water calculator uses current readings, target values, volume, and product assumptions to create a cautious planning estimate. Follow labels and retest before acting.

Primary result

Estimated free ammonia 0.0343 mg/L
Total ammonia 1 mg/L
pH 7.8
Temperature 77°F
Caution level Lower

Free ammonia is estimated as a pH-dependent fraction of total ammonia nitrogen.

Aquarium toxicity depends on pH, temperature, salinity, species, and test accuracy. If fish are stressed, act conservatively and consult aquatic guidance.

Quick answer

This pool/water calculator uses current readings, target values, volume, and product assumptions to create a cautious planning estimate. Follow labels and retest before acting.

Best for: comparing realistic scenarios before acting. Not for: final professional guidance, emergency decisions, or replacing product labels and local requirements.

How to use the calculator

  1. Enter the measurements, quantities, costs, or target values requested above.
  2. Adjust optional assumptions such as waste, overhead, product strength, retention days, or multipliers.
  3. Read both the main result cards and any warning notes. The warnings are part of the answer, not fine print.
  4. Use the share, copy, or print/PDF controls when you want to save the scenario.

What the results mean

The primary result is the main number to use first. Supporting cards show the inputs, ranges, assumptions, or follow-up checks that explain how to interpret it.

Decision notes for this calculator

Status: Safety-sensitive planning aid

pH drives the free-ammonia fraction sharply, so test accuracy matters.

What to do next

If livestock/fish are stressed, act conservatively and consult aquatic guidance rather than waiting on a modeled number.

Formula / methodology

Free ammonia is estimated from total ammonia nitrogen (TAN) and the pH-dependent ammonia/ammonium split. The current interim model uses NH3 = TAN ÷ (1 + 10^(9.25 − pH)) and displays the freshwater planning assumption until temperature/salinity source constants are covered in the source notes.

Assumptions and limitations

  • Inputs are assumed to be measured accurately and entered in the units shown.
  • Rounding is intentional so the result is easier to use in real decisions.
  • Vendor-specific behavior, local code, product labels, and regional pricing can override a generic calculator.
  • Health, legal, tax, emergency, structural, chemical, and other high-risk decisions need qualified guidance beyond a web calculator.

Example calculation

Input: TAN 1.0 mg/L and pH 7.8. The pH-dependent fraction gives about 0.0343 mg/L free ammonia. Any detectable ammonia can be dangerous, so retest and follow aquarium water-change guidance.

The worked example uses the same default scenario so the formula can be followed without running JavaScript.

Common mistakes

  • Confusing total ammonia nitrogen with free ammonia.
  • Ignoring that higher pH and temperature increase the free-ammonia fraction.
  • Assuming saltwater and freshwater constants are interchangeable.
  • Waiting to act when fish show stress or ammonia is detectable.

FAQ

What formula does this page use?

Dose estimates use desired ppm change, water volume, and a product/concentration factor.

What changes the result the most?

Total ammonia nitrogen, pH, temperature, salinity/species sensitivity, and test accuracy drive estimated free ammonia risk.

How should I use this result?

Use it as a planning estimate and compare important decisions with product documentation, labels, quotes, local code, or qualified guidance.

Why does this page show warnings?

Warnings call out assumptions that can materially change the result or create safety, cost, or reliability problems.

Can I share this scenario?

Yes. The share button copies a URL with the current inputs, while the main page remains the base calculator URL.

Sources and assumptions

References used for this calculator:

  • Formula basis: Estimated free ammonia is calculated as a pH-dependent fraction of total ammonia nitrogen using the displayed TAN, pH, and temperature context.
  • Limitations: Toxicity varies by species, salinity, temperature, test kit accuracy, acclimation, and water chemistry; stressed fish require conservative action.
  • Method note date: June 24, 2026.
  • Editorial scope: CalculatorShelf editorial math check; not veterinary/aquaculture certification.
  • When to contact a professional: Consult aquarium or aquatic-veterinary guidance for fish distress or high readings.

Method details

Updated: June 24, 2026. Calculation method: AQUARIUM_AMMONIA-1.0. Availability: planning aid while the page is improved, sourced, or differentiated.