What Does It Mean When A Goldfish Gets Black Spots. Usually, when a goldfish is floating on the water’s surface, it is a good indicator that he has died or that he is close to it. Continued exposure to high ammonia levels can lead to the development of black patches, even before the levels begin to come down.
If your fish or his fins are turning black, you'll need to test your water and take a look at his neighbors. If your goldfish suddenly develops patches of black scales or black areas in the fins, this can be a sign of healing, usually from an injury or ammonia poisoning. As goldfish age, their color changes in sometimes unexpected ways.
