How long does aquarium cycling take before adding fish?
Written by
Hoang Long
Reviewed by
Prof. Henry Webster, Ph.D.The cycling of an aquarium sets up beneficial bacteria that change the fish waste poisons to less toxic compounds. This biological filtration prevents the dangerous ammonia poisoning. The length of time is dependent on the methods used and environmental conditions. I have cycled tanks in 8 to 10 days, depending on these important factors.
Temperature Control
- Warmer tanks 84-86°F (29-30°C) accelerate bacterial reproduction
- Cold water below 70°F (21°C) slows bacterial growth dramatically
- Daily temperature stability prevents bacterial die-offs
Bacterial Starters
- Quality refrigerated starters cut cycling time by 50%
- Proper dosing: 50 ml per 38 liters (10 gallons)
- Direct application into filter media boosts colonization
Ammonia Management
- Maintain 2-4 ppm ammonia to feed bacteria colonies
- Daily testing prevents underfeeding or toxic spikes
- Pure ammonium chloride works better than fish food
The traditional fishless cycling of an aquarium typically takes 4-8 weeks for the bacterial colonies to develop naturally within the aquarium. Test ammonia and nitrite every day. I recommend using liquid test kits instead of strips, as they are more accurate. It takes patience; however, it does pay off with a biological filtration that provides long-term protection for your fish.
Acceleration methods, which combine temperature-controlled seeded media and bacterial starters, can reduce cycling time to 10-14 days. However, caution should be taken when rushing because of an incomplete colony (or incomplete colonies), which will collapse later. A true completion of cycling should always be confirmed by testing of 0 ammonia, 0 nitrite & increasing [nitrates] for three consecutive days.
Never introduce fish until after the cycling is complete, and you are sure of the results of the tests when the ammonia and nitrites both remain at nil after more than 48 hours after dosing. In that way, the New Tank Syndrome deaths will be avoided. The fish will flourish in a properly cycled environment.
Read the full article: Aquarium Cycling Process: Essential Beginner's Guide
