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Large White Spot on Betta Fish — What is It?

Large White Spot on Betta Fish — What is It?

One of the most popular pet fish is the betta, also called the Siamese fighting fish. Bettas may have white spots due to fungal infections, Lymphocystis virus, tumors, wounds, abscesses, or egg spots.

Many of these problems are treatable. With the exception of egg spots, white spots should not be ignored and often do not get better on their own.


Large White Spot on Betta Fish

A large white spot on the underside of a female betta fish is normal and not a sign of illness. Other reasons for white spots on bettas’ heads, bodies, or fins are illnesses such as ich, fungal diseases, abscesses, or tumors. Ich and fungal diseases are highly contagious to other fish.



Ich is so common that all people who keep fish will encounter it at some point. Ich is short for Ichthyophthirius multifiliis, the name of the minuscule protozoan parasite that causes white spot disease, also called ich.

This may start out as one spot and spread all over the body. Spots are usually small as if the fish was sprinkled with salt, but sometimes the spots can get quite large.

The infected fish often rubs its body on the sides of the tank or along objects in the tank and may stop eating. Eventually, fins may tear or rot.

Sick bettas, never very vigorous swimmers to begin with, become even more motionless and will often stay at the top of the water, gasping for air.

Ich can kill fish if it’s left untreated. Treat by:

  • Changing at least one quarter of the tank water daily.
  • Gradually raise the tank’s temperature to 86 degrees Fahrenheit, as ich does better in colder water.
  • Increase the tank’s oxygen level by adding air stone to it.
  • Add ich medication to the water. There are various OTC medications for ich, most of which contain formalin and malachite green.
  • Wash your hands after touching the water, as ich can live on the skin. If you put your hands in another tank, then the ich comes off your hands to infect the new tank.


Fungal Infections

Next to ich, fungal infections are the most common reasons for white spots to appear on a betta. Ich can cause fungal infections.

Spots can be quite large and usually look fuzzy. They appear anywhere on the body, mouth, or fins.

If left untreated, the spots become so large that it looks as if the betta has swum into a cotton ball. Fish can die from fungal infections.

Treatment for fungal infections in bettas is much like for ich. Do frequent water changes, raise the water temperature, and use over-the-counter medication.

It’s also recommended to test the water to see if it’s normal. Any sudden change in pH, nitrate, or ammonia can keep a fungal infection going.

Remove any sharp aquarium ornaments, as rubbing up against these may cause injuries that a fungal infection can take advantage of.


Lymphocystis Virus

As its name suggests, this is a virus. It’s seen in both saltwater and freshwater fish, including bettas. It’s not as common as ich.

Sometimes, when the virus starts, parts of the body look as if covered by a hazy film. The virus causes larger, more bumpy spots on fish.

Sometimes the spots resemble tiny heads of cauliflower. The spots usually appear on the fins, but sometimes they show up on the gills or the mouth. Sometimes the spots turn pink.

Unlike ich, lymphocystis virus is rarely fatal, unless nodules grow on the gills, or the betta picks up a secondary infection caused by the virus. Sometimes, it even resolves on its own.

However, it is recommended to make frequent water changes. Good water quality helps the fish to survive.

Feed the best quality food to boost your fish’s immune system. No medication is known to help treat infected fish.

Humans cannot catch this virus from their fish.


Other Possible Causes of White Spots on Bettas

As the name Siamese fighting fish suggests, bettas are aggressive. Males will not tolerate other males.

They also may not tolerate other freshwater aquarium fish, especially gouramis. When getting into fights with other fish, they often wound themselves.

Sometimes, wounds can look like white spots. They sometimes look fuzzy.

All fish can get tumors, including bettas. They can also appear as white spots which may turn into white growths.

Unfortunately, tumors are incurable. What looks like a tumor, but isn’t, is actually an abscess.

This can be caused by fighting, bacterial infections, or an accidental injury against a sharp edge of an aquarium decoration. Abscesses can often be successfully treated with antibiotics made for fish.


A Note About Egg Spots

A bright white spot appears on the underside of female bettas when they become sexually mature at three months old. It appears in between the ventral fins (fins nearest the head) and the anal fins.

This spot may resemble an ich spot. Female egg-laying fish have an organ where the eggs leave the body called an ovipositor tube.

That bright white spot is the ovipositor tube. It’s completely normal.

Before, it was easy to tell female bettas from male bettas. Females always had short fins and far less vibrant colors than males.

In recent decades, this has changed. Females have been bred to have longer fins and brighter colors.

One sure way to tell females from males is to check for the egg spot. They are also less aggressive than males.


Frequently Asked Questions About Large White Spot on Betta Fish


What is a Betta Egg Spot?

Egg spots are different from ich in that they are small and only on female bettas. It’s a small, often bright white spot on the belly between the front (ventral) and back (anal) fins. The spot is the organ where eggs are released, called an ovipositor tube.


Is Ich Contagious to Humans?

People can’t get the symptoms of ich from their fish. However, ich can live on a person’s skin. It’s important to wash your hands after treating fish for ich so you do not accidentally contaminate another tank by putting ich-covered hands into the water.


Will Ich Go Away on Its Own?

Ich always gets worse over time because spores fall off of infected fish to spread all throughout the aquarium. If nothing is done, ich will eventually kill all of the fish in the tank. Never ignore ich.


The Least You Need to Know

There are many reasons why your betta has large white spots. The most common reasons are ich, fungal infections, and (in females) egg spots.

Other reasons include wounds, abscesses, tumors, and lymphocystis virus. Most of these causes are treatable.

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