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.
Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.
Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.
Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.
Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.
Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.
How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.
What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.
How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.
Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.
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