1. Changes in water temperature, 2. High density of fish, 3. Water pollution. The water temperature of goldfish fluctuates from cold to hot. The unstable growth environment of goldfish will cause physical discomfort and serious death. If you do not pay attention to the type and quantity of goldfish when raising them, Keeping many fish together can easily lead to the death of the goldfish. In addition, the water in the fish tank will deteriorate and cause diseases. The goldfish will infect each other, but the owner will not notice the death of the goldfish.