Betta fish discoloration can be caused by a variety of factors. Here are the common causes and corresponding solutions:

Natural Physiological Changes
Aging Factors: Older bettas (over 1 year old) naturally fade due to declining pigment metabolism, which is an irreversible sign of aging.
Genetic Traits: For example, marble-colored bettas undergo periodic color changes based on gene expression. Juveniles may develop different colors after shedding their protective coloring.
Environmental Stress
Water Quality Fluctuations: Sudden temperature changes (more than ±2°C), abnormal pH levels (ideal range 6.5-7.2), or excessive ammonia can cause stress-induced discoloration.
Solution: Use a heater to stabilize water temperature at 25-28°C, replace 1/3 of the water weekly, and monitor nitrite levels.
Inappropriate Lighting: Direct strong light can cause fading, while long-term dim environments may also affect color development. It’s recommended to provide 4-6 hours of soft lighting daily and avoid direct sunlight.
Nutritional and Health Issues
Dietary Deficiencies: Lack of color-enhancing components like astaxanthin and carotenoids can lead to dull coloring.
Improvement Method: Feed frozen bloodworms, brine shrimp, or spirulina-based food, and supplement with high-protein live bait twice a week.
Disease Impact: Conditions such as ich or water mold are often accompanied by pale body color. Isolate the affected fish and treat with 0.3% saltwater or methylene blue.
Behavioral and Psychological Factors
Breeding Period Traits: Male bettas may fade after losing their breeding colors, and females may also experience temporary discoloration post-spawning.
Stress Reactions: Transportation, tank changes, or fights can cause temporary fading. Allow 3-5 days of quiet recovery, and the color should return.
Key Handling Recommendations
Emergency Measures: If discoloration is accompanied by fin damage or rapid breathing, immediately isolate the fish and test water quality.
Long-Term Maintenance: Use dark-colored substrate and background panels to enhance coloration, and add almond leaves to reduce stress.
Breed Selection: Solid-colored bettas are less prone to fading than marble-colored varieties. When purchasing, check for natural, even coloring.