Fantail Goldfish Fin Turning Black

my goldfish fins are turning black
If water is not properly filtered and cleaned, the toxins can cause burns to the goldfish causing fin to turn black.

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

  • Ammonia Burns

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.

  • Water temperature

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.

Click here to watch a water change tutorial.

2 thoughts on “Fantail Goldfish Fin Turning Black”

  1. John McLarnon

    We have three goldfish and a painted turtle in our 30 gallon aquarium. The turtle is about six inches in diameter and the largest goldfish is about one pound. We changed the water the other day, as it was starting to turn that lovely green colour. But, shortly after adding the required chemicals of chlorine remover and such; we noticed that it looked like our big goldfish started to act as though he is now blind and the smaller of the three has now got black on the tips of his fins and a black patch under his right eye.

    Can goldfish go blind? and could the black spots on the fins be a result of the old water in the aquarium, having too much ammonia??

    Is there anything that can be done to help the fish that might now be blind ??

    Thank you any and all help that can be passed on.

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