Velvet in Betta Fish: Causes, Symptoms, Treatment, and Prevention

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By Linh Nguyen Updated on 02 Feb 2023

Bettas are beautiful, vibrant fish that are popular in the aquarium world. They come in a variety of colors and patterns, and their long fins make them especially stunning to look at. But did you know that bettas can also suffer from a condition called velvet?

Velvet is a type of infection that causes the fish's body to be covered in a fuzzy, yellowish growth. It can be very dangerous to bettas, and if left untreated, it can even lead to death.

The good news is that velvet can be treated, and bettas can make a full recovery. In this article, we'll take a closer look at what causes velvet, the symptoms to watch out for, and how to treat it.

A betta fish with velvet

A betta fish with velvet

1. What is velvet betta?

Velvet disease is also known by other names such as Rust disease, Coral disease, or Gold Dust. This disease is a common and often fatal condition that affects freshwater fish. The disease is caused by a parasitic dinoflagellate called Oodinium pilularis. This parasite attaches to the fish's skin and gills, causing irritation and inflammation. The disease can spread quickly through an aquarium or fishpond, and infected fish often die within a few days. 

2. What is parasitic dinoflagellate - Oodinium pilularis?

Oodinium pilularis is a single-celled organism that belongs to the phylum Dinoflagellata. This phylum also includes other well-known organisms such as coral and algae. The dinoflagellates are a group of over 2,000 different species of marine and freshwater plankton. Many dinoflagellates are bioluminescent, meaning they can produce their own light. 

Dinoflagellates are mostly harmless, but Oodinium pilularis is a parasitic species that prey on fish. The parasites attach to the fish's skin and gills, causing irritation and inflammation. The disease can spread quickly through an aquarium or fishpond, and infected fish often die within a few days. 

3. How does velvet betta spread?

Velvet disease is most commonly seen in goldfish, but it can also affect other freshwater fish such as bettas, guppies, and koi. The disease is not contagious to humans or other animals. 

The velvet betta parasite has a two-stage life cycle. The first stage is the dinospore stage, in which the parasite produces swimming spores that infect fish. The second stage is the trophont stage, in which the parasite attaches to the fish's skin and gills and begins to reproduce. 

The dinospores are typically introduced into an aquarium or pond through live food, such as brine shrimp. Once the dinospores come into contact with a fish, they attach to the fish's skin and gills and begin to reproduce. Within a few days, the dinospores will transform into trophonts. The trophonts will continue to reproduce on the fish's skin and gills, causing irritation and inflammation. The disease can spread rapidly through an entire aquarium, and infected fish usually die within days if not treated promptly.

a betta fish is suffering from velvet disease

4. Causes

There are several different things that can cause velvet on betta fish. The most common cause is the parasite Oodinium pilularis. This parasite is very small, and can only be seen with a microscope. It attaches to the fish's skin and gills and feeds on their blood.

Besides, velvet can also be caused by other parasites, such as Cryptocaryon irritans, or by bacterial infections.

In addition, one of the most common is a water quality issue. If the water that your betta is in is not clean and free of toxins, it can start to develop velvet disease.

Another common cause is stress. If your betta is stressed out from its environment or from other fish in the tank, it can also start to develop velvet disease.

Poor nutrition can also lead to velvet disease. If your betta isn't getting the proper nutrients and vitamins, it can make them more susceptible to developing the disease.

Finally, if your betta has any cuts or abrasions on their body, this can also lead to velvet disease. The bacteria that causes the disease can enter through these open wounds and start to infect the fish.

5. Symptoms and pictures

The symptoms of velvet disease vary depending on the stage of infection. In the early stages, infected fish may show no visible signs of illness. As the disease progresses, symptoms may include:

5.1. Tiny gold or red spots on the body

When a betta fish has velvet disease, it will often have tiny gold or red spots on its body. That's why this disease has other names such as rust disease or gold dust disease.

These spots are actually the parasites that cause velvet disease. As the parasites multiply, they begin to infect the skin and gills of the fish, causing the characteristic velvety growth.

In some cases, they may develop velvet-like growth on their skin and gills. This can cause the fish to have difficulty breathing, and may eventually lead to death. Velvet disease is often fatal if not treated quickly and properly.

5.2. Loss of appetite

When a betta has velvet disease, one of the most common symptoms is loss of appetite. The fish may stop eating altogether or may only eat very small amounts. In some cases, the fish may continue to eat but may do so less than usual. This can lead to weight loss and poor health. If you notice your betta fish losing interest in food or appearing to be thinner than usual, check for other signs to rule out velvet disease.

5.3. Lethargy

Another symptom of velvet disease in bettas is lethargy. Fish with this disease may appear listless and uninterested in their surroundings. They may also swim less actively than usual, and may spend more time at the bottom of the tank. In severe cases, fish may become completely immobile. Lethargy is often one of the first signs of velvet disease, so it is important to be aware of it.

5.4. Clamped fins

Manifestations of this symptom are the fins will appear to be sticking together and may be frayed or ragged in appearance. In some cases, the fish may also scratch itself against objects in the tank in an attempt to relieve irritation. Velvet disease can also cause a loss of appetite, lethargy, and difficulty breathing. If left untreated, velvet disease can be fatal.

5.5. Difficulty breathing

With velvet disease, your betta often shows signs of difficulty breathing. The fish may appear to be gasping for air at the surface of the water or they may spend more time than usual lying at the bottom of the tank. In severe cases, the fish may start to display signs of distress, such as hanging vertically in the water or swimming erratically. If you notice any of these symptoms, your fish needs to be diagnosed and treated as soon as possible.

Causes of velvet on your betta

6. Treatment

Velvet disease is a common ailment in bettas, and can be quite serious if left untreated. This disease is caused by a parasitic dinoflagellate called Aurantiomonas. Fortunately, it is relatively easy to treat, and with prompt treatment, most fish will make a full recovery. There are a few different treatments for velvet disease, depending on the severity of the case.

Here are some treatments

6.1. Use aquarium salt in the early stage

If caught early, often times a simple salt bath will suffice.

The first thing you'll need to do is change the water in their tank. Make sure to clean the gravel and remove any debris. Then, increase the water temperature to 86 degrees Fahrenheit (30 degrees Celsius) and turn off all lights in the tank. 

This will help strengthen the fish's immune system and limit the growth of flagella - the cause of disease.

Finally, you'll need to give your betta a salt bath. To do this, simply fill a small container with water from the tank (make sure it's the same temperature!) and add 1 teaspoon of salt per gallon of water.

You need to be careful to increase the temperature of the water and add salt to the water slowly to avoid the fish being shocked by the rapidly changing environment.

Do a 50% water change every day for three days, then reduce the frequency to every other day for another week.

After two weeks, your betta should be free of the parasites and on the road to recovery!

aquarium salt

If the case is more severe, you may need to treat it with an anti-parasitic medication, such as formalin or copper sulfate. These medications can be quite harsh on bettas, so it is important to follow the directions carefully and not over-medicate.

In this case, you should isolate your betta in a hospital tank. This will allow you to better monitor the betta and ensure that they are receiving the proper treatment.

Here are detailed instructions

6.2. Use copper sulfate

To treat your betta fish with copper sulfate, you will need to purchase a copper sulfate solution from your local pet store. 

When treating velvet disease in betta fish, it is important to follow the instructions carefully and not to overdose the fish with copper sulfate. The recommended dosage of copper sulfate for betta fish is 1 teaspoon (5 ml) per 10 gallons (40 L) of water. This should be added to the aquarium over a period of time, and the water should be changed every day during treatment. The treatment should last for at least two weeks but can be extended if necessary.

If you are unsure about how to treat your betta fish for velvet disease, it is always best to consult a veterinarian or experienced aquarist for advice.

6.3. Use formalin

Formalin is a common treatment for velvet disease, and when used properly, can be effective in treating the disease.

Formalin should be used at a concentration of 0.5-1.0%. For example, if using a 2% formalin solution, you would mix 2ml of formalin with 98ml of water to make a 100ml solution. This solution can then be added to the betta fish tank at a rate of 1ml per 10 liters (2.64 US gallons) of water.

Treatment time will vary depending on the severity of the disease, but as a general rule, treatment should continue for 7-10 days.

When using formalin to treat velvet disease in betta fish, it is important to monitor the fish closely. Formalin is a toxic substance, and if the concentration is too high, it can cause serious harm to the fish. Signs that the concentration of formalin is too high include gasping at the surface of the water, loss of appetite, lethargy, and increased mucus production. If you see any of these signs, immediately stop adding formalin to the tank and do a partial water change to remove some of the formalin from the water.

In addition to monitoring the fish closely, it is also important to keep an eye on the nitrite and ammonia levels in the tank. Formalin can cause an increase in these levels, so regular water changes will be necessary to keep the levels safe for the fish.

Formalin is a powerful treatment for velvet disease, but it is also a toxic substance. If used properly, it can be effective in treating the disease, but if not used properly, it can cause serious harm to the fish. As such, it is important to use formalin only under the guidance of a qualified veterinarian or fish health expert.


With proper treatment, most bettas will make a full recovery from velvet disease. However, it is important to remember that once a betta has had velvet, they are more susceptible to future outbreaks. Therefore, it is important to practice good tank maintenance and water quality control to help prevent future problems.

Here are some ways to help you prevent this disease effectively.

Clean living environment helps prevent fin rot disease

7. Prevent velvet

There is no surefire way to prevent your betta from contracting velvet, as the disease can be caused by a number of different factors. However, there are some things you can do to reduce the risk of your betta getting sick. 

  1. Don't buy live food that has not been properly quarantine. This includes brine shrimp, bloodworms, and daphnia. 
  2. If you must buy live food, quarantine it in a separate tank for at least two weeks before adding it to your main tank. 
  3. Clean your aquarium or pond regularly. Remove any deceased fish promptly. 
  4. Disinfect anything that comes into contact with your tank, including your hands, nets, and decorations. 
  5. Keep your tank free of excessive algae growth. 
  6. Use a filter with a high turnover rate. 
  7. Be sure to properly cycle your tank before adding fish. 
  8. Avoid overfeeding your fish. 
  9. Keep a close eye on your fish for any signs of illness and consult a veterinarian if necessary. 

Following these guidelines should help you to prevent your fish from getting velvet disease.


While parasitic dinoflagellate - Oodinium pilularis (velvet betta) is not well known, it can be deadly to your fish. This article has outlined what velvet betta is, how it spreads, and how to treat it. It is important to be vigilant in looking for the symptoms of velvet so that you can get treatment started as soon as possible. Please let me know in the comments below if you have any questions about this topic or betta care in general. I am always happy to help!

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