How much household ammonia to add to reach your target level while cycling a tank without fish. Because bottle strengths vary, treat this as a starting point and confirm with your test kit.
A fishless cycle grows the filter bacteria that convert ammonia to nitrite and then nitrate, before any fish go in. You feed those bacteria with a small, steady supply of ammonia. Dose to 2 to 4 ppm, let it drop, and re-dose, until the tank clears both ammonia and nitrite within 24 hours. See the full walkthrough in fishless cycling and the theory in the nitrogen cycle explained.
Enough to reach 2 to 4 ppm, then let it fall and re-dose. The amount depends on your volume and the strength of your bottle. This calculator converts the stated % ammonia to the nitrogen reading your kit shows and gives the millilitres to add; confirm with a test after dosing.
Plain household ammonia with no perfume, colour or surfactants. Shake the bottle: if the foam lingers it has detergent and is no good. Common strengths are 5 to 10% NH₃.
A target of 2 to 4 ppm is typical. Higher wastes ammonia and can stall the cycle. Add roughly half the dose, wait an hour, test, and top up.
A guide only. It assumes a solution of the stated % ammonia (NH₃) at about 0.9 g/ml, converts to the nitrogen basis your test kit reads (NH₃ is 82% nitrogen by weight), and works out the millilitres to raise the level from current to target across your volume. Real bottle strengths are often unlabelled or approximate, so testing after dosing is the only way to be sure. A target of 2 to 4 ppm is typical for a fishless cycle.