Ammonia dosing calculator

How much ammonia to add to reach about 2 ppm. Works with liquid ammonia of known strength, and with powder or bottles of unknown strength through one quick test.
What are you adding?
Target ammonia, ppm
Tank volume
Ammonia in the tank now NH3/NH4
ppm
Ammonia strength from the label, %
Use plain ammonia: the label should list only ammonia and water, with no soap, scent or colour.
Fill in the fields above to see how much to add.

How it’s calculated

  • mg of ammonia = ppm × litres
  • ml = mg ÷ (strength % × 10)
A 10% solution holds about 100 mg of ammonia in every ml, so strength × 10 gives mg per ml.

How much ammonia does a tank need?

To cycle a tank you raise ammonia to about 2 ppm and let the bacteria eat it. One ppm is one milligram per litre, so a 100-litre tank needs 200 mg of ammonia to go from 0 to 2 ppm.
Liquid ammonia comes in different strengths, from a few percent in household bottles to 10% or more in products made for aquariums. A 10% solution holds about 100 mg of ammonia in every ml, so those 200 mg are 2 ml. The calculator does this sum for any volume and strength.

Choosing an ammonia source

Use ammonia with nothing else in it: the ingredients should say ammonia and water only. Soap, perfume and colour can harm the bacteria and, later, the fish. If the liquid foams when you shake the bottle, it contains detergent — leave it on the shelf.
Powdered ammonium chloride works too, but its strength varies between brands and is rarely printed clearly. That is what the calibration mode is for.

Calibration when the strength is unknown

  • 1.
    Add a small, measured amount — for example 1 ml, a few drops or a quarter teaspoon.
  • 2.
    Let it mix for about 30 minutes with the filter running.
  • 3.
    Test ammonia and enter what you added and what the test shows.
  • 4.
    The calculator works out how much one unit raises your tank and how much more you need.
It scales in a straight line: if 1 ml raised the tank by 0.5 ppm, reaching 2 ppm from zero takes 4 ml. The result also shows this full dose for next time, so you only calibrate once per product.

More is not faster

Extra ammonia doesn’t speed the cycle up. Above about 4 ppm it slows the bacteria down, and the calculator warns you when the target or your current reading is that high. Dose to about 2 ppm and top up again when a test shows less than 1 ppm.
If fish are already in the tank, don’t add ammonia at all — the fish produce plenty. Test daily instead and change 30⁠–⁠50% of the water when ammonia or nitrite reaches 0.25 ppm.

Litres, gallons and rounding

Switch between litres and US gallons next to the volume field; gallons are converted to litres (one US gallon is 3.785 litres) before the formula runs. Results are rounded to what you can actually measure: two decimals below 1 ml, one decimal below 10 ml, and whole drops.
For small amounts, a syringe or a pipette from a pharmacy is far more precise than a spoon. For a very small tank you can dilute the ammonia first: 1 ml mixed into 9 ml of water gives a solution one tenth as strong, so enter a tenth of the original strength.