Fantail Goldfish Fin Turning Black

These are 4 causes that can be easily rectified.
1. Ammonia Burns
2. Goldfish naturally change color
3. The tank is too small
4. Water temperature

When you think your goldfish is turning black it’s distressing, but it’s important to note any changes in behavior and eating habits of the goldfish.

my goldfish fins are turning black

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

The issue of fantail fins turning black is quite common and might be cause for alarm or completely harmless.

Major changes in normal habits along with changing color are signs there could be a serious problem.

In most cases the black color is a sign the healing process has already begun, and further treatment is not necessary.

Causes of your goldfish fins turning black

#1 Ammonia Burns

This is the most common reason and is a result of the tank not being properly cleaned. Food that’s not eaten and fish waste causes toxins to build in the water.

If the water isn’t 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 doesn’t return. In time, the goldfish should return to normal color.

#2 Goldfish can naturally change color

It’s possible that there’s nothing wrong at all. Goldfish are known to change colors. The change could be just a normal process for the fish.

#3 The tank or aquarium is too small

The tank isn’t large enough for the number of goldfish. People often begin with a small tank or bowl when buying their first fish. The water very quickly gets stagnant if it’s not cleaned regularly. Toxins then infect the tank and cause illness.

#4 Water temperature

It’s hard to keep the water temperature regulated in a small bowl. The small size of the tank easily warms and causes infections in goldfish and you’ll find your fantails fin turning black.

Simply investing in a larger tank minimizes this problem.

Purchasing a 10 or 20 gallon tank for your fish is generally sufficient to ensure the goldfish has plenty of room to swim. The size recommended depends of course on the number of fish living in the tank.

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’s probably no reason for concern.

If you’re still worried it’s best to completely clean out the tank because keeping a clean fish tank is the ideal way to avoid diseases and unnecessary infections.

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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