Bacteria need food. Without dosed ammonia OR fish waste OR uncured live rock, no bacteria grow. Add 2-4 ppm ammonia or seed material.
Tap water has chloramine. Without dechlorinator, chloramine kills bacteria as fast as they grow. ALWAYS dose Seachem Prime with water changes.
Below 72°F, bacteria reproduce 3-5x slower. Heat tank to 78-82°F to accelerate cycling.
Old test kits drift. Verify expiration date. Some test kits read false-positive ammonia in tanks dosed with Prime (the bound ammonia still shows on Salifert tests).
Cycling takes 4-6 weeks for fishless cycle without bottled bacteria. Dr. Tim's One & Only or Bio-Spira speeds to 7-14 days.
If you treated for disease before cycling, antibiotics killed the cycling bacteria. Restart with fresh bottled bacteria.
Browse all cycling troubleshooting articles. Pair with the cycle ETA calculator + fishless cycle ammonia calculator.