It can be concerning if you find that your goldfish has suddenly and abnormally developed a reddish hue on their body because goldfish are lovely ornamental fish that come in a number of different colors. The gills, tail, spots, or other areas of their bodies may all exhibit this redness.

Some goldfish may be naturally colored red or may turn reddish as they begin to mature. However, poor water quality is also linked to redness in goldfish, which can result in burns on your fish.

A goldfish may turn red for a variety of causes, including a natural color shift or a serious condition that should be investigated. You can learn about the reasons why your goldfish might be turning red in this post, along with what you can do to help.

What Is Causing Your Goldfish’s Red Turn?

1. Changes in Natural Coloration

When goldfish are young, color changes are completely normal. The majority of goldfish variations can change their color and pattern throughout the first several years of development. The amount of sunlight they receive or the food they are fed may also have an impact on these color changes.

Chromatophores, pigmented cells that reflect visible light and give fish their color, are in charge of regulating the color in fish. The chromatophores responsible for red coloration, erythrophores, are what give a goldfish its metallic appearance. When exposed to more sunshine, such as in a pond, goldfish may take on a reddish hue.

2. Ammonia Intoxication

When the nitrogen cycle (the establishment of helpful bacteria) in an aquarium has not matured properly or if this cycle has been broken in an aquarium, ammonia poisoning will ensue. This could lead to a rise in ammonia levels, which would burn your fish and result in the development of red spots and streaks on your goldfish. Red streaks on your goldfish are a clear sign that the water quality in your aquarium needs to be checked. Due to their high sensitivity to ammonia, goldfish often tolerate levels below 0.25 ppm before beginning to exhibit symptoms of ammonia poisoning.

Your goldfish may start to exhibit crimson streaks and gasping for oxygen near the water’s surface, which can eventually turn black and be followed by lethargy, loss of appetite, clamped fins, and other symptoms.

3. Red Pest Disease

Poor water quality ponds and aquariums frequently experience this problem. A bacterium (Bacterium cyprinid) may attach to your goldfish as a result of the poor water quality, which can alter the slime coat of the fish. The most vulnerable goldfish to this problem are those with compromised immune systems.

Maintaining consistently clean water in your goldfish aquarium and pond will help prevent this disease, which is simpler to treat. Red pest illness appears as red or pink spots on your goldfish’s body, usually beginning at the tail’s base. Clampped fins and an abundance of slime coat formation are other indicators.

4. Septicemia

A goldfish with this problem will develop redness and swelling beneath its scales. In addition to becoming red, goldfish will also behave strangely and become lethargic. Advanced bacterial infections that affect your goldfish may be the source of this, and advanced stages of these red skin sores are usually challenging to treat.

The most frequent causes are infections and stress, although other reasons include open wounds exposed to unclean water.

5. Ulcers

An ulcer typically manifests as a huge red area on the fish’s body and is the result of extended exposure to bacterial infection in water of extremely low quality. Even while it can sometimes be treated, it calls for immediate action as well as significant management and fish husbandry modifications.

How to Care for Goldfish Who Are Turning Red

If your goldfish is naturally becoming red, there is little you can do to prevent this from happening unless you restrict the amount of sunlight they receive or alter their diet.

You must perform a significant partial water change to diluted the ammonia when treating a goldfish that has become red owing to water quality issues, such as high levels of ammonia. To aid in their speedier recovery, you may also administer salt dips to your goldfish in a separate therapy tank while following the manufacturer’s dosage instructions.

Before putting your goldfish inside the tank, make sure the nitrogen cycle has completed in the aquarium. When necessary, you can also use filter material like ammonia chips to assist the aquarium absorb excess ammonia.

The proper treatment should be administered to goldfish who have septicemia or red pest illness in order to assist the germs die off. In this case, water quality is also crucial, so you should make sure to replace the water frequently and maintain a decent filtration system running to keep the water clean.

Goldfish with bacterial infections should be treated with potent drugs in a treatment tank, such as methylene blue or malachite green and other bacteria-killing fish medications. From the standpoint of the influence on the environment, their use is debatable. The medication’s packaging will typically provide instructions for dosage and length of treatment, which should be carefully followed.


Use a water testing kit to see if the ammonia levels have increased before noticing that your goldfish are starting to turn red. If you discover that the water in your goldfish’s tank is of good quality, it is best to investigate the potential that your goldfish may have a bacterial infection that requires quick treatment for a full recovery. For the greatest confirmation of a diagnosis, consult a veterinarian.