Hole in Head of the Oscar Fish – Disease & Treatment

Hole in the head disease is one of the most common kinds of diseases that affect freshwater fish, especially fish species such as Oscars, discus, and cichlids.

The other name for a hole in the head disease is Freshwater Head and Lateral Line Erosion. This disease can prove to be fatal if it is left untreated and can leave permanent scarring on the head of the fish even after the disease has been taken care of.

There are many culprits of this disease such as poor nutrition.

Oscar Fish Hole in Head Disease & Treatment (Video)

This article will discuss the causes, symptoms, and treatments of this unfortunate disease.

Causes of hole in the head disease

Nobody knows the exact cause of hole in the head disease yet, but there are some theories that link this disease to certain conditions.

The presence of even one of the conditions may lead to the birth of hole in the head disease but with a combination of two or three of those factors, the spreading of this disease is imminent.

Given below are all of these factors that contribute to hole in the head disease.


One of the most common contributors of hole in the head disease is a flagellate parasite, known as Hexamita. This parasite is known to affect the abdominal cavity, kidneys, gallbladder, and the intestinal tract of the fish.

As the disease grows, lesions of hole in the head become visible. These lesions later open up and begin to discharge white threads which are home to parasitic larvae.

As the disease begins to spread all over the body of the fish, fungal or bacterial infections begin to develop in these openings and soon lead to other diseases or sometimes even death.

Mineral or Vitamin Deficiency

Another theory is that mineral and vitamin deficiencies in the fish lead to this disease.

Many aquarists have linked the use of activated carbon to this. According to them, the activated carbon removes the minerals present in the water and so, this increases the chances of development of the disease.

On the other hand, the deficiency of minerals may also be due to the presence of Hexamita that prevents the absorption of minerals and vitamins in the intestinal tract of the affected fish.


The disease may also occur if the fish is stressed. Factors such as poor water quality, oxygen deficiency, improper nutrition, and overcrowding; all cause stress among fish.

Weakened Immune system

Older fish that have a weaker immune system as compared to younger fish are also susceptible to this disease as their immune system is not strong enough to fight the disease.

Signs and symptoms

The signs and symptoms of hole in the head disease include pitting type lesions on the head and the lateral line of the fish. These holes may be small at the beginning or the initial stages of the disease; but if the disease is not treated and the environment remains the same, the holes might increase in size and become larger.

The color of the fish also fades away and they lose their luster. The enlarged lesions will eventually create severe infection after which the fish will become ill, lose its appetite, and ultimately die.

Testing for chemical levels in the water

Once you identify the hole in the head disease, then it’s best to act quickly and test the quality of the water in the fish tank. Carry out a nitrite, ammonia, nitrate, and pH test immediately. This should be preferably done using a liquid test kit.

The hole in the head disease does not just appear out of nowhere and in the majority of the cases, it is caused by the poor water conditions. Stress among the fish has been commonly caused by the fish being exposed to drastic fluctuations in the temperature of the water and this occurs when the water is changed.

If you are able to identify the water conditions as the culprit of the disease, then you should immediately carry out a large water change in order to eliminate and remove as much toxic material as possible. In this situation, a product called prime may be useful as it helps to get rid of chlorine and also detoxify nitrite and ammonia.


You need to keep in mind that ammonium is also present in the fish tank water, which is a harmless version of ammonia. When you will test the water for ammonia, you may end up getting a reading for ammonia levels in the tank.

There is nothing to be alarmed about in this situation. In reality, the results would be of ammonium, not ammonia. You should carry out water changes until the level of nitrites and ammonia are zero and they remain like that.


Nitrate is is considered to be the by-product of nitrite and ammonia. It is not as toxic as ammonia or nitrite, but it is better to keep it at a very low level. The high levels of nitrates can cause stress among the fish which will eventually lead to the development of the hole in the head disease to the fish.

So, do not let the nitrate levels increase more than 40ppm. You can keep the level of nitrates low by carrying out frequent water changes.

A proper healthy diet

One of the reasons for the hole in the head disease is said to be a diet that lacks mineral and vitamins.

An improper diet actually weakens the immune system of the fish which makes it more susceptible to the disease. In order to keep your fish healthy, it is very important that you provide it with a healthy and nutritious diet.

You can do this by providing your fish with good-quality pellets as they will include all the important nutrients that your fish requires to stay healthy and grow. Many pet owners provide their Oscar fish with live feeders such as goldfish, but this is very unhealthy for it.

Feeders are mostly bred in very large numbers. They are not really properly taken care of and may carry parasites that can make your fish very sick. The best way to provide your fish with the nutrition it needs is to give it peas, carrots, and pieces of courgettes. This is actually the easiest way you can introduce vitamins in the diet of your fish.

Shrimps, snails, earthworms, cockles, mussels, prawns and mealworms are also a good choice to keep your fish’s immune system well and strong. All of these are easily available in the supermarket, pet shop, fish store and you can even harvest them in your own little garden.


A good fish diet contains a lot of vitamins which your fish needs, but it would not hurt to provide them with extra vitamin supplements. You can add a few drops of vitamins in the water of the fish tank every day.

Another great way to provide your fish with the vitamins it needs is to soak the fish food in the vitamin supplements before giving it to your fish.

Treatment in later stages

The early stages of hole in the head disease are relatively easy to treat and you can cure your fish just by improving the water conditions of the tank. Remove the toxins and keep the levels of nitrates low.

On the other hand, the later stages of hole in the head disease are trickier to treat. In that case, medicines like Metronidazole can help. Metronidazole, more commonly known as Flagyl, is a medicine that can be found both in powder as well as tablet form.


Hexamita parasite is the main culprit of the hole in the head disease and can be easily cured by a medicine known as Metronidazole. You can add the medicine to the water in the fish tank or medically administer it by adding it to the fish’s food. There are many ways you can add the medicine to the food of your fish easily.

If you purchase Flagyl in tablet form, then you should crush it into powdered form. You can ask your veterinarian for the right amounts of medicine to use; but if you do not want to go to such lengths, then do not worry; the medicine comes with instructions regarding the right amount of dosage.

You can take some frozen fish food and then leave it to partially thaw. Then add the powder to the partially frozen food and then refreeze the entire mixture. You can then feed your fish the frozen food.

You can also use dry pellet food to do your bidding. Crush the pellet by making use of a mortar and then crush it until the food is in powdered form.

Add the powder of the medicine to the crushed food and then bind them back together by using gelatin which you can easily purchase at your local food store. You need to mix the gelatin and the food until you have a pasty mixture, then make small balls of the mixture.

Keep in mind not to make the balls too big as your fish might have difficulty eating it. This whole process will barely take half an hour and then you’re ready to feed the fish. Remember not to feed your fish any other kind of food until the whole medication cycle is completed. Feed this food to your fish for about a week at the bare minimum.


The best way to prevent such diseases in your fish is to provide them with the best living conditions. Test the water of the fish tank frequently, keep the ammonia and nitrate levels low and provide the fish with high-quality food.

Related questions

The presence of holes on the body of the fish but the fish is not sick? This is totally possible, many fish like the Oscars have tiny pits all over their body. These are called sensory pits. These holes are arranged in circles and are completely normal.

What are the physical symptoms of hole in the head disease?

The hole in the head disease have many signs, some are mentioned below

  • Mucous Trailing from the holes
  • Large holes and sores
  • Loss of appetite
  • Lethargy
  • White sores around the eyes and on the top of the head

What are some of the natural fish feeds? Natural fish feeds are organisms that can be found in wild water bodies such as annelids, worms, zooplankton, phytoplankton, insects and mollusks etc.

Other sources


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