The issue of the fantail fins turning black is quite common. It may be cause for alarm, or it may be completely harmless.
It’s distressing when you think your goldfish is turning black, but important to note any changes in behavior and eating habits of the goldfish.
Major changes in normal habits along with the changing color can be a sign of a serious problem.
In most cases, the black color is a sign the healing process has already begun, and further treatment of the goldfish is not necessary.
Possible causes of your goldfish fins turning black
The most common reason for fins turning black. These are caused from the tank not being properly cleaned. Food that is not eaten and fish waste causes toxins to build in the water. If the water is not properly filtered and cleaned often, the toxins can cause burns to the goldfish. The black color is a sign the infection is healing, and cleaning out the tank properly will help ensure the infection will not return. In time, the goldfish should return to normal color.
Goldfish can naturally change color
It is possible that there is nothing wrong at all. Goldfish are known to change colors. The change could be just a normal process for the fish.
Tank or aquarium is too small
The tank may not be large enough for the goldfish. Many people begin with a small tank or bowl when buying their first goldfish. The water can easily get stagnant if it is not cleaned regularly. Toxins can quickly infect the tank and cause illness.
It’s difficult to keep the water temperature regulated in a small bowl. The small size of the tank can easily cause infections in goldfish and result in your fantails fin turning black. Simply investing in a larger tank can minimize this problem. Purchasing a 10- or 20- gallon tank is generally sufficient to ensure the goldfish has plenty of room to swim. It’s also easier to install a filter system to a larger tank.
If the fish is acting normally, the water is clean, and the water temperature is fine, there is probably no reason for concern.
If there is some concern, it’s best to completely clean out the tank. Keeping a clean fish tank is the ideal way to help avoid diseases and unnecessary infections.