According to relevant research and practical experience, the water change frequency for betta fish should be comprehensively considered based on factors such as fish tank capacity, seasonal changes, and filtration systems. The following are scientific recommendations:
I. Basic Water Change Frequency
Small tanks (below 1.5 liters): Change 20% of the water daily to maintain water quality stability.
Medium tanks (3-5 liters): Change 1/3 of the water every 48 hours, or adopt a regular schedule of "changing water once every three days".
Large tanks (over 10 liters): Change 1/4 to 1/3 of the water weekly, following the principle of "1/3 water change + 48-hour standing".
II. Adjustments for Special Cases
Without a filtration system: Shorten the interval to once every 3-4 days; in high-temperature summer, it is recommended to change water every 2-3 days.
Thai betta fish (single breeding in a small tank): Full water change can be done depending on water quality, but water must be aged in advance to remove chlorine.
Low-temperature winter period: Bacterial activity slows down, so the interval can be extended to once every 15 days.
III. Key Precautions
Water temperature control: The temperature difference between the new water and the tank water should be ≤1°C to avoid stress.
Water quality treatment: Tap water needs to be exposed to the air for 3 days or 暴晒 (sunlight) for 1 day to remove chlorine.
Water change volume: Do not change more than 1/2 of the water at a time; 1/3 is recommended for safer operation.
IV. Signs of Water Quality Deterioration
If the fish show white eyes, fin rot, or decreased activity, immediately change 1/3 of the water daily and test the ammonia-nitrogen concentration (should be <0.05ppm). Scientific monitoring shows that failing to change water for more than 5 days will significantly reduce the survival rate of betta fish.