Aquarium Cycling with Ammonia Method: Fishless Cycle Protocol

Cycling a tank without livestock is the kindest way to establish a nitrogen cycle, and dosing pure ammonia is the cleanest way to do it. Aquarium cycling with ammonia method uses a measured dose of household-grade ammonium hydroxide to feed the bacteria you want, without the variability of fish food or shrimp. This guide from Gensou Aquascaping at 5 Everton Park lays out the dosing maths, the test schedule, and what you should see week by week. Done properly, you finish in 3-6 weeks with a tank that handles full stocking on day one.

Quick Facts

• Target ammonia level: 2-4 ppm (NH3+NH4+ as N)
• Use pure ammonium hydroxide — no fragrance, no surfactants, no soap
• Dr Tim’s Ammonium Chloride and Fritz Fishless Fuel are the cleanest sources
• Cycle duration: 3-6 weeks depending on temperature and seeding
• Cycle complete when 2 ppm ammonia clears in 24 hours and nitrite is zero
• Expect 20-40 ppm nitrate at the end — water change before stocking
• Heat to 28-30°C to accelerate; pH 7.4-8.0 ideal for nitrifiers

Why Fishless Beats Fish-In

Cycling with fish in the tank works, but it exposes the animals to weeks of measurable ammonia and nitrite — both of which damage gills permanently even when not visibly fatal. Fishless cycling pushes ammonia far higher than any fish would tolerate, building a much larger bacterial colony than fish-in could produce, with no welfare cost. By the time you add stock, the filter handles full bioload immediately.

Sourcing Ammonia In Singapore

Pure household ammonia (also sold as ammonium hydroxide solution) used to be available at hardware shops; supply has dried up. The reliable options now are:

• Dr Tim’s Ammonium Chloride — sold via Shopee for $18-25 a bottle, lasts 5-10 cycles
• Fritz Fishless Fuel — similar price point, similar concentration
• Lab-grade ammonium chloride powder — cheapest, but requires accurate scales

Avoid janitorial ammonia, “lemon ammonia”, and any product with surfactants, dyes, or perfume. The additives kill the bacteria you are trying to grow and never fully wash out.

Dosing To 2-4 ppm

Both Dr Tim’s and Fritz are formulated so 4 drops per US gallon (roughly 1 ml per 15 L) raises ammonia to about 2 ppm. For a 100 L tank, dose 6-7 ml to land near 2 ppm; double for 4 ppm. Test 30 minutes after dosing once water has circulated, and adjust in subsequent doses based on the actual reading from your test kit.

API Freshwater Master Test Kit handles ammonia, nitrite, and nitrate adequately at this stage. Salifert and Hanna Checkers give finer resolution if you want it.

The Three Phases

Week 1-2: ammonia stays high while ammonia-oxidising bacteria (Nitrosomonas) establish. You will see ammonia start to drop and nitrite begin to climb. Week 2-4: nitrite rises sharply, often to 5+ ppm, while nitrate appears as nitrite-oxidising bacteria (Nitrospira) catch up. Week 4-6: both ammonia and nitrite drop to zero within 24 hours of dosing, and nitrate climbs steadily. The cycle is complete.

Re-Dosing Schedule

Re-dose ammonia to 2 ppm whenever the reading drops below 0.5 ppm. Early in the cycle this is every 3-5 days; late in the cycle, every 24 hours. The increasing dosing frequency is the clearest sign your bacteria population is growing.

Do not let ammonia run out completely for more than a day or two — starved bacteria die back, and the cycle stalls. Equally, do not push ammonia above 5 ppm; high concentrations inhibit Nitrospira and slow the second phase.

Temperature, pH, And Oxygen

Nitrifiers work fastest at 28-32°C, which Singapore tanks hit naturally without a heater. pH 7.4-8.0 is the sweet spot; below 6.5 the bacteria slow dramatically and below 6 they stop. Soft PUB tap water sometimes drifts low, so check KH at week 2 and add a pinch of bicarbonate if pH falls under 7. Aerate well — nitrifiers are obligate aerobes and a starved-of-oxygen filter cycles painfully slowly.

Confirming Completion

The test: dose ammonia to 2 ppm in the evening, test 24 hours later. If both ammonia and nitrite read zero, the cycle is complete. Do this for two consecutive days to confirm; the first zero result can be a fluke if the bacteria are right at the edge of capacity.

At completion you will typically see 20-60 ppm nitrate, depending on how many ammonia doses you put through. A 50% water change before stocking brings nitrate down to a safe starting point.

Speeding Things Up

Three accelerators work: borrowed seeded media from a cycled tank (fastest, can finish in 7-14 days), bottled bacteria like Dr Tim’s One and Only or Fritz TurboStart 700 dosed at the start (cuts time by 30-50%), and keeping temperature at 30°C. A bare tank cycle without any seeding at room temperature can stretch to 8 weeks at the long end.

Common Mistakes

Dosing the wrong ammonia (with surfactants), letting the cycle stall on a stuck nitrite phase, and stocking heavily on day one with no pre-cycle water change to bring nitrate down. Patience and a test kit solve all three.

Related Reading

• Aquarium Fishless Cycle Ammonia Guide
• Fishless Cycling Step by Step
• Aquarium Cycling Timeline
• Aquarium Fish In Cycle Safe Method
• Seeded Media Instant Cycle Guide