The death of betta fish is usually closely related to the breeding environment, management methods, or health problems. Improper breeding conditions, disease infections, stress responses, or natural aging are the main causes of death. The following are the specific reasons and preventive measures:
Water Quality Problems: The Most Direct Killer
Ammonia/Nitrite Poisoning
Cause: Failure to change water in a timely manner or a malfunctioning filtration system, resulting in the decomposition of fish feces and uneaten food, which produces toxic substances (ammonia, nitrite).
Symptoms: The betta fish floats to the surface to breathe, its gills turn red, its body turns black, and its activity is sluggish.
Prevention: Change 1/3 - 1/2 of the water weekly, regularly test the water quality with a water quality tester, and install a small - scale filtration system (such as a sponge filter).
Chlorine/Heavy Metal Poisoning
Cause: Direct use of tap water without de - chlorination or water sources containing heavy metals.
Symptoms: The betta fish twitches, the mucous membrane on its body surface peels off, and its gills fester.
Prevention: Treat the water with a water quality stabilizer (such as a de - chlorinator) before changing the water, or expose the tap water to the sun for more than 24 hours.
Sharp pH Fluctuations
Cause: Frequent water changes or the use of water sources with different pH values, resulting in stress in betta fish.
Symptoms: The betta fish's body color becomes dull, its appetite decreases, and its fins shrink.
Prevention: Keep the pH stable (6.5 - 7.5) and use the same - source water when changing water.
Oxygen Deficiency: The Hidden Danger of a Static Water Environment
Insufficient Dissolved Oxygen
Cause: A too - small container (such as < 5 liters), too - high water temperature (> 28℃), or deteriorated water quality.
Symptoms: The betta fish frequently floats to the surface, breathes rapidly, and its gills open wide.
Prevention: Use a wide - mouthed container to increase the water surface area, or increase oxygen through an air pump or filtration system.
Carbon Dioxide Accumulation
Cause: A completely closed container or too many aquatic plants consuming oxygen during nighttime respiration.
Symptoms: The betta fish floats to the surface in the morning and is slow - moving.
Prevention: Avoid completely closing the container and reduce the density of aquatic plants.
Temperature Out of Control: The Threat of Extreme Temperatures
Low Temperature (< 20℃)
Cause: Lack of heating in winter or a malfunctioning heater.
Symptoms: The betta fish's metabolism slows down, its appetite decreases, and its body color turns gray.
Prevention: Use a heater to maintain the water temperature at 24 - 28℃ and install a thermometer for monitoring.
High Temperature (> 32℃)
Cause: Lack of sunshade in summer or a malfunctioning heater.
Symptoms: The betta fish breathes rapidly, its gills are red and swollen, and it may even die.
Prevention: Avoid direct sunlight and use a fan or cold water to cool down.
Disease Infections: Invasions of Bacteria/Parasites
Bacterial Diseases (such as Gill Rot, Enteritis)
Cause: Poor water quality, wound infection, or the introduction of pathogens by new fish.
Symptoms: The body surface is ulcerated, the gills are white, and the feces are abnormal.
Treatment: Isolate the sick fish, bathe it with antibiotics (such as yellow powder), and at the same time improve the water quality.
Parasitic Diseases (such as Ichthyophthirius, Dactylogyrus)
Cause: The introduction of new fish with parasites or water pollution.
Symptoms: White spots on the body surface, frequent rubbing against the tank wall, and increased mucus in the gills.
Treatment: Raise the temperature to 30℃ and add salt (1‰), or use special anthelmintic drugs.
Fungal Infections (such as Saprolegniasis)
Cause: The fish's body is exposed to dirty water after being injured.
Symptoms: White fluffy substances on the body surface and slow movement.
Treatment: Isolate the sick fish and bathe it with methylene blue or malachite green.
Stress Responses: Damage from Sudden Environmental Changes
Physical Stress
Cause: Frequent movement of the fish tank, strong water flow 冲击，or noise interference.
Symptoms: The betta fish's fins shrink, its body color darkens, and it refuses to eat.
Prevention: Keep the environment stable and avoid suddenly changing the water temperature, light, or decorations.
Chemical Stress
Cause: Misuse of drugs or sudden changes in water quality (such as a sudden pH change).
Symptoms: The betta fish twitches, its body surface is congested, and it may die quickly.
Prevention: Change the water or use drugs gradually and avoid over - dosage.
Social Stress
Cause: Improper mixed - breeding (such as living with aggressive fish).
Symptoms: The betta fish's fin rays are torn, it hides, and it refuses to eat.
Prevention: Keep the betta fish alone or mix - breed it with gentle fish (such as guppies).
Malnutrition or Over - feeding
Malnutrition
Cause: Long - term feeding of a single type of food (such as only dry feed).
Symptoms: The betta fish's body color is dull, its growth is slow, and its immunity decreases.
Prevention: Provide a variety of foods (such as live bloodworms, freeze - dried shrimps, and special pellet feeds).
Over - feeding
Cause: Excessive feeding amount leads to uneaten food polluting the water quality.
Symptoms: The betta fish's abdomen is swollen, it floats to the surface, and the water quality deteriorates.
Prevention: Feed 1 - 2 times a day, and it is advisable that the food is eaten up within 3 minutes.
Natural Aging and Genetic Defects
Aging - related Death
Cause: The lifespan of betta fish is usually 2 - 5 years, and the organ functions of elderly individuals decline.
Symptoms: Reduced activity, decreased appetite, and fading body color.
Treatment: Provide a comfortable environment and reduce interference.
Genetic Defects
Cause: Inbreeding leads to deformities or low immunity.
Symptoms: Abnormal body shape of the betta fish and easy - to - get diseases.
Prevention: Select healthy breeding fish and avoid inbreeding.
Summary: The Keys to Preventing Betta Fish Deaths
Keep the water quality clean: Regularly change the water, test the indicators, and use a filtration system.
Control the temperature and humidity: Maintain the water temperature at 24 - 28℃ and avoid extreme temperatures.
Reduce stress: Provide a stable environment and avoid frequent changes.
Feed scientifically: Have a diverse diet and control the feeding amount.
Treat in a timely manner: Isolate the sick fish and use drugs immediately when diseases are found.
Through careful management, betta fish can live healthily for several years. If a betta fish suddenly dies, it is recommended to check the water quality, temperature, and recent operations (such as water changes, feeding) to find out the cause and make improvements.