Red Gills On Goldfish: Causes, Symptoms, And Treatments

Goldfish are one of the most popular house pets. They are easy to raise, diverse in species, and have eye-catching appearances that make your aquarium and your room more aesthetic.

However, that does not mean that it is disease-free. They are exposed to many ailments, one of the most common being red gills on goldfish. What do you need to know, and how can you treat them?

Red Gills On Goldfish: Causes, Symptoms, And Treatment 

Many reasons can lead to this problem, and you need a more detailed and thorough examination to know for sure. However, in short, some of the most common causes include the following:

  • Bacterial gill disease
  • Gill flukes
  • Ammonia poisoning

goldfish with red gill

Bacterial Gill Diseases

This is a popular culprit that many fish have to face. It affects both saltwater and freshwater fish, particularly juvenile ones. It is caused by various bacteria, the most common are Aeromonas, Flavobacteria, and Pseudomonas.

They thrive in filthy, crowded environments. The contaminated equipment or contact with sick ones can also spread it.


Bacteria are not the primary cause of illness, like physical injury or incubating parasites, yet they can exacerbate the situation, especially in poor water and nutrition conditions.

Some common symptoms that you can identify that your goldfish got bacterial gill diseases:

  • Gills be inflamed and turn brown
  • Unusual red spots on fins and gills
  • Labored and rapid breathing
  • Mucus may be secreted by the gills.
  • They can gasp for oxygen.
  • Appetite loss


BGD is frequently a secondary infection caused by another underlying condition. It is difficult to diagnose the specific bacteria without a gill biopsy. Because the bacteria are so prevalent, they can quickly reinfect them after treatment.

The affected fish must be quarantined in another tank and treated with broad-spectrum antibiotics. To make medicated food, use Fritz Maracyn 2 or API Fin And Body Cure since they are one of the most effective ones to reduce bacterial infections. This task is challenging, and you must be patient.

Gill Flukes

If your water is in good condition, you may face gill flukes. Home aquariums are prone to parasite infestations.

Gill flukes, also known as Dactylogyrus species, are monogenean parasites on gills. They use two anchor pairs to attach to the fish’s gills and feed on the blood and tissue.

gill flukes on goldfish


Your fish will have trouble breathing as the parasites are causing inflammation and tissue damage in the gills.

  • Surface gasping or labored breathing
  • Excess mucus and red, inflamed gills
  • The body is opaque with a mucus coating.
  • Rubbing and flicking
  • Swimming in erratic patterns or darting around the tank
  • Appetite loss


To treat gill flukes, use a Parasite Treatment such as PraziPro or API General Cure. These medications will aid in removing flukes from your fish and improve their health.

If they are stressed due to poor water quality or overcrowding, the flukes can multiply and trigger an outbreak.

Ammonia Poisoning

In the aquarium, ammonia poisoning is another cause of death. Though it is not a common parasite, it can be found in tanks, especially during the setup process.

The ammonium level in a well-established tank can rise suddenly or gradually over time for the reasons listed below.

  • Because of the chemical outage, your filter isn’t working properly.
  • Crammed fish food and decaying leaves
  • The use of aquarium medication resulted in the loss of beneficial bacteria.
  • Unexpected changes in water conditions


  • Bloody gills
  • Fish tend to gasp or hard breathing
  • Appetite loss
  • Lethargic situation


First, test the ammonia levels in your water. If it’s too high, you must perform an immediate water change. Removing decaying leaves and food from the tank is also critical, as these also increase the ammonia levels.

Lastly, the best way to avoid ammonia poisoning is to monitor your water parameters regularly.

Ways To Avoid Red Gills On GoldFish 

Prevention is better than cure. Although you already know the causes and treatments, it is better to lower the chance of diseases in fish by taking preventive methods.


First, make sure their habitat is of good quality. 

Water quality is frequently the most overlooked aspect of a tank. It should be clean and free of toxins when your fish is in water 24/7. Ammonia, nitrates, or nitrites should all be zero parts per million. If they aren’t, you’ll need to change the water.


Improper diet leads to malnutrition, weakened immune system, or other related diseases. However, this does not mean that you feed them as much as possible.

They require a well-balanced diet of fats, protein, and carbohydrates to stay healthy. Feeding time and the number of meals per day also need to be considered appropriately.


Stress is one of the most common causes that kill your fish. They are more likely to become ill if they are stressed. Many factors can contribute to this, including overcrowding, poor water quality, bullying, or even a sudden change in the aquarium.


Should Gills On Fish Be Bright Red? 


Usually, it will not be easy to recognize the red lights of disease and signs of healthy fish. However, bright red gills are a good indicator of a healthy one. It can fade to light pink with age.

What Color Should Goldfish Gills Be? 

As mentioned above, some gill colors below might be suitable for your goldfish in most cases. However, remember to perform regular check-ups to ensure their overall health.

  • Bright red
  • Normal red
  • Pinkish red

Even if your fish gills live up to the standard for color but show strange signs such as loss of appetite, lack of activity, or any other sign, they can get sick or have some health issues. 

normal color of goldfish's gill


In short, when you see the red gills on goldfish, doing a thorough general check is what you should do. There are three common issues that you may have to face in this case:

  • Bacterial gill diseases
  • Gill Flukes
  • Ammonia Poisoning

With each of them, we’ve provided you with detailed treatment guidelines. Apply it and observe your fish situation for timely solutions.