Here are scientific recommendations for water change frequency in betta fish tanks, integrating different feeding conditions and seasonal factors:
I. Basic Water Change Frequency
Small Fish Tanks (1-5 liters)
Without a filtration system: Change 25%-30% of water every 2-3 days.
With a filtration system: Extend to once a week.
Medium Fish Tanks (5-20 liters)
Regular schedule: Change 20%-30% of water weekly.
New tank initial period: Change 5% of water daily for the first two weeks to stabilize water quality.
Large Fish Tanks (over 20 liters)
Change 20%-30% of water every 1-2 weeks.
II. Seasonal Adjustments
High-temperature summer: Bacteria multiply rapidly—change water every 2-3 days.
Spring & autumn: Change water once a week.
Low-temperature winter: Extend to once every 15 days.
III. Key Operation Guidelines
Water Change Volume Control
Do not change more than 1/3 of total water volume per session.
Avoid full-tank water changes (destroys the nitrification system).
Water Quality Pretreatment
Tap water must be aged for 3 days or sun (sunlight) for 1 day to remove chlorine.
Temperature difference between new water and tank water should be ≤1°C.
Emergency Water Change Triggers
Change water immediately if ammonia-nitrogen > 0.2ppm or nitrite > 0.1ppm.
When bettas show abnormal behaviors like surface gasping or lateral lying.
IV. Notes for Special Breeds
Thai betta: Recommend changing 1/3 of water weekly; thoroughly clean debris at the tank bottom before (water change).
Chinese betta: With a filter, change water once every 10-12 days.
Tip: Regularly monitor ammonia-nitrogen and nitrite levels with water test kits to adjust water change frequency dynamically.