1. Water quality: Water quality is one of the most critical factors in fish tanks. Fish need proper water temperature, pH value and balance of chemicals such as ammonia nitrogen, nitrite and nitrate. Improper water quality will have a negative impact on the health of fish, and even lead to death. Therefore, it is very important to test the water quality regularly and make necessary adjustments.

2. Suitable fish tank environment: The size of fish tank, decorations, vegetation and water flow all play an important role in the survival and comfort of fish. If the tank is too small or overcrowded, the fish may feel stressed and uncomfortable. In addition, the lack of proper shelter or escape route will also increase the pressure of fish. Ensuring a suitable fish tank environment can improve the survival rate of fish.

3. Improper diet: Incorrect feeding and eating habits are also a common factor leading to fish death. Different kinds of fish have different dietary needs, so it is very important to provide suitable fish food. Overfeeding or lack of nutrition may have adverse effects on fish health. At the same time, excess food may lead to deterioration of water quality and increase organic pollutants in water.

4. Diseases and infections: Fish are susceptible to diseases in unsuitable environments. Common fish diseases include fungal infection, bacterial infection and parasitic infection. When the immune system of fish is weakened, they are more vulnerable to diseases. Regularly observe the behavior and appearance of fish, and pay attention to any abnormal symptoms, so as to take timely treatment measures.

5. Pairing and fighting: Fighting and aggressive behavior may occur between different species in fish tanks where many kinds of fish live together. These fights may lead to wounds, stress and diseases, which in turn lead to the death of fish. Ensure that compatible fish are selected and provide enough shelter and space, which can reduce the occurrence of fighting.