Fishless Cycle Ammonia Calculator
Cycle your new tank without risking any fish. Enter your water volume and target ammonia level — we'll tell you how much ammonia to add.
Calculate ammonia dose
How fishless cycling works
Fishless cycling grows the beneficial bacteria your filter needs before any fish arrive. You feed the bacteria with pure ammonia instead of fish waste:
- Dose ammonia to 2–4 ppm (this calculator assumes standard 10% clear ammonia: mL = liters × ppm × 0.01, about 20 drops per mL).
- Wait for nitrite to spike, then fall back to zero as the second bacterial colony establishes.
- Confirm the cycle: dose to 2 ppm again — if ammonia and nitrite both read zero 24 hours later, you're cycled.
- Do a large water change to bring nitrates down, then add fish gradually.
Fishless cycle tips
- Only use clear, unscented ammonia with no surfactants. Shake the bottle — if it foams like dish soap, don't use it.
- Household ammonia strength varies (5–10%), so always verify with a liquid test kit after dosing.
- Keep the filter running the whole time and the water warm (78–82°F) — bacteria colonize faster.
- Seeding with filter media from an established tank can cut cycling time dramatically.
Frequently asked questions
How long does a fishless cycle take?
Usually 2–6 weeks. Warmer water, seeded filter media and consistent ammonia dosing all speed it up.
What ammonia should I use for fishless cycling?
Clear, unscented household ammonia with no surfactants or perfumes — or an aquarium ammonium chloride product, which is dosed more precisely.
How do I know when the cycle is finished?
Dose ammonia to 2 ppm; if both ammonia and nitrite read zero 24 hours later, the tank is cycled. Then do a big water change and add fish slowly.
Can I cycle with fish food instead of ammonia?
You can, but it's messy and imprecise — rotting food is hard to dose and fouls the water. Pure ammonia is cleaner and measurable.