Calculate how much ammonia solution to add to reach your target ppm for fishless nitrogen cycle startup. Works with any ammonia concentration percentage.
Fishless cycling with pure ammonia is the modern, ethical standard for establishing a new aquarium's biofilter without exposing fish to toxic spikes. The hard part is dosing the right amount of ammonia to reach (but not exceed) a target ppm in a known water volume, then keeping it there until the biofilter consumes the full daily dose within 24 hours. This calculator turns tank volume, target ppm, and your ammonia solution concentration into the exact milliliters to add.
From your tank volume in liters and target total ammonia in ppm we compute total grams of NH3-N required. Knowing the percentage concentration of your ammonia hydroxide solution (typically 5-10% in household ammonia, ignoring scented or surfactant-laden products), we back-solve the milliliters of solution to dose. The calculator also warns when target ppm exceeds 4 ppm (which can stall the nitrite-oxidizing bacteria) and suggests an upper limit of 2-3 ppm for steady cycling.
Enter your tank volume, the target ammonia concentration in ppm (2 ppm is standard), and the concentration percentage of your ammonia solution (check the label). The calculator outputs the mL to add.
Use pure, unscented ammonia with no surfactants. Shake the bottle — if it foams, it contains surfactants and will kill bacteria. The label should list only ammonium hydroxide (NH4OH) and water.
Test ammonia daily. Once levels consistently drop from 2 ppm to 0 within 24 hours AND nitrite also drops to 0, your cycle is complete. Do a large water change (80%) to remove built-up nitrate before adding fish.
Fishless cycling establishes beneficial bacteria (Nitrosomonas and Nitrobacter) in your filter before adding fish. You dose ammonia to feed the bacteria, who convert it to nitrite, then to nitrate. The cycle is complete when ammonia and nitrite both drop to 0 in 24 hours.
Most fishless cycling guides recommend starting at 2–4 ppm ammonia. 2 ppm is a good starting point for most tanks. Avoid going above 4–5 ppm, as very high ammonia can actually inhibit bacterial growth.
Use pure ammonia with no surfactants or additives — the bottle should list only ammonium hydroxide (NH4OH) and water. Common concentrations are 9–10% and 25–29%. Check the label and enter the percentage into this calculator.
The cycle is complete when: ammonia drops from 2 ppm to 0 within 24 hours, and nitrite also drops to 0 within 24 hours. Test daily. A complete cycle typically takes 4–8 weeks with pure ammonia, less with a bacterial starter.
Dose ammonia every 1–2 days to keep levels at 1–2 ppm once bacteria establish. Let levels drop to 0 before re-dosing to mimic a fish load. Do a large water change (80%) before adding fish to flush accumulated nitrate.