Goldfish may die from chemical, nitrite, nitrate or ammonia poisoning. Lack of oxygen and food are other possible causes. Too much feeding, which causes constipation, may also lead to the demise of goldfish.
Like humans, goldfish may be infected with harmful bacteria, which can cause them to die. Shock from sudden change in water temperature or pH levels may also cause goldfish death.
Goldfish are expected to live for five to 12 years, according to GoldfishFacts.net. The website recommends feeding the goldfish fiber-rich foods and keeping it in a medium-sized or 5-gallon aquarium to make sure that the fish gets enough oxygen.