Why Is My Goldfish Turning Black?

If you have a pet goldfish at home, you already know how painful it is to find your goldfish slowly turning black. The search query may sound weird or funny to ordinary people, but it disheartens the goldfish owners the moment they read it. Goldfishes turn black because of excess ammonia in the water. The ammonia burns their skin and causes dark or black colored spots on their body. In a worst-case scenario, the condition can even kill a fish or cause irreparable damage to its health. Goldfishes turn black when water in the aquarium or tank are not replaced regularly.