Cycling is simply building the bacteria that convert ammonia → nitrite → nitrate. Most cycling frustration comes from two things: testing without a plan, and making big changes that reset progress. In Australian tap water, one extra detail matters more than people realise: KH (buffer). Low KH can cause pH swings that slow bacterial growth and make cycles feel “stuck”.
What you actually need
- a running filter (sponge/HOB/canister)
- a heater (24–26°C speeds the cycle and keeps it stable)
- a liquid test kit for ammonia, nitrite, nitrate, and pH
- patience and a simple routine
Step-by-step cycling plan
- Start the filter and heater and let the tank run for a day so temperature stabilises.
- Add a small ammonia source (a pinch of food every few days, or a measured ammonia source if you use one).
- Test every 2–3 days. You’re waiting for ammonia to rise, then fall, and for nitrite to rise, then fall.
- Don’t panic-water-change constantly. Small changes are fine if ammonia/nitrite spike very high, but large frequent changes can slow the cycle by removing the fuel.
- When ammonia and nitrite both read 0 for several days (with feeding), the tank is ready for a light stocking.
Where KH fits in
Beneficial bacteria prefer stable pH. If your KH is very low (often seen in very soft water areas), pH can drift or crash, slowing the cycle. A gentle way to stabilise is crushed coral in the filter or a small buffer addition — but do it slowly and measure results.
Mistakes that stall cycles
- Overfeeding the cycle: rotting piles create huge spikes and instability.
- Cleaning filter media under tap water: chlorine can wipe bacteria out.
- Adding too many fish at once: a “cycled” tank can still be overwhelmed by a big jump in bioload.
If your cycle feels stuck, it’s usually a routine problem, not a mystery. Keep a simple log (date + ammonia/nitrite/nitrate + what you changed). Patterns show up quickly once you write them down.
