Hole in the Head Fish Disease – Causes, Symptoms, Treatment and Care

hole in the head fish disease

Hole in the Head Fish Disease – An Introduction

The Hole in the head fish disease is one of the most common parasitic infectious diseases that occur in freshwater fishes. This disease is also called as 

  • HLLE disease
  • Lateral Line Erosion
  • Lateral Line disease

Aquarium owners, especially the owners of public display aquariums, can incur losses in a big way if the fishes in their aquarium get affected by this disease. The disease results in the fish getting badly disfigured. The other fish in the aquarium, too, can get affected by this disease. Early detection is extremely critical to ensure the wellness of the fish affected by the disease.

The Hole in the head fish disease mainly affects freshwater fish species such as Oscars, cichlids, and discus fishes. The disease starts with the appearance of small pits on and around the fish’s head. The pits then spread to the lateral line and then to the fins. The Hole in the head disease in fish can be fatal, and the fishes affected by this disease need timely treatment.

If you are an aquarium owner, the list below will give you a basic idea of the Hole in the head fish disease causes and what to do about them.

Causes of the disease Precautions to be taken
Hexamita Parasite Medication – Metronidazole Isolation of infected fish
Nutritional deficiencies Diet supplementation with nutrient-rich fish food.
Poor water quality Regular water testing for toxins. Regular water change.
Presence of activated carbon in water Removal of chemical filtration systems. Regular water testing. Regular water change.
Absence of nutrients in the water Regular water changes. Installing good water filtration systems. Adding aquarium salt regularly.
Unclean aquarium Regular aquarium cleaning Regular water change.

Hole in the Head Disease – Causes

Scientists have not been able to pinpoint the exact cause for the occurrence of a hole in the head disease in fish. Researchers believe there are three main factors responsible for the condition in fish

  • Pathogens
  • Quality of water
  • Resistance levels of fish

Hole in the head fishes disease can occur due to the following reasons:

Hexamita Parasite

The Hole in the head disease in fishes in mainly caused by parasites called Hexamita. These parasites are present in a dormant state inside the body of fishes. They do not cause any harm. But if the immune system of the fishes is compromised due to any reason, the parasite may start affecting the fish. 

Hexamita will start infecting the intestinal tract initially. The infection then spreads to other organs for the fish like kidneys, spleen, abdominal cavity, and gall bladder.

With the spread of the infection, the fish will start developing small pits or holes on its head with receding skin. The pits will then spread all over the head and onto the lateral line of the fish, and finally, the fins also develop these pits.

The pits will now start releasing white thread-like substances. This discharge contains parasitic larvae, which will then contaminate the water around. If the infection remains untreated, the holes or lesions keep getting bigger.

The fish can also develop other secondary bacterial and fungal infections, which will eventually lead to the death of the fish.

Nutritional deficiencies in fish

Hole in the head disease in fishes can also occur due to nutritional deficiencies. The disease can occur in a fish due to the deficiency of a single or a combination of nutrients- Vitamin C, Vitamin D, Iodine, Calcium, and Phosphorous. Nutrition deficiency will lead to the weakening of the immunity system of the fish, thereby causing the disease.

Nutritional deficiencies can also lead to the increased presence of Hexamita in the fish’s body. This will then lead to malabsorption of nutrients from the food, and thus the fish can get affected by the disease.

Activated Carbon

Scientists believe that the presence of activated carbon in water may remove some of the beneficial nutrients and minerals that are present in that water. As a result, fish may not get the nutrition they require, and this may lead to an increase in the incidence of the disease.

Poor Quality of Water

Inadequate water quality can increase the incidence of the Hole in the head disease in fishes. Water in aquariums may sometimes contain higher amounts of nitrate, nitrite, and ammonia. A higher quantity of nitrate in water is associated with a higher incidence of the Hole in the head fish disease.


Overcrowding of fish is a common problem in aquariums. When a large number of fishes are present in limited space, they all have to share limited resources like water and nutrients. Fishes have to face conditions of malnutrition and unclean water. If one of the fishes gets affected by the disease, it will quickly spread to all other fishes, since the disease is contagious.

Over filtration of water

Some aquarium owners may use chemical filtration methods to clean up the water in their aquarium. Over-filtration can rob the aquarium water of all its nutrients leading to the occurrence of the Hole in the head fish disease.


In fishes, stress is also responsible for causing the Hole in the head fish disease. Large and frequent temperature fluctuations, overcrowding of the fish, poor water quality, insufficient water changes, lack of essential nutrients in the water, polluted water in the aquariums – all these factors can cause stress on the fish’s metabolism. If the fish is not able to stand the stress, its immune system can weaken, ultimately leading to the Hole in the head disease.

To know more about different Saltwater and Freshwater Aquarium Fish Diseases, click this article “Aquarium Fish Diseases: Causes, Symptoms, and Treatments“.

Hole in the Head Fish Disease – Symptoms

As the name suggests, the most common Hole in the head fish disease symptom is the appearance of holes on the head of the fish.

Here is the full list of the Hole in the head fish disease symptoms:

  • Early symptoms: one or two holes appear on the head of the fish. These holes are generally symmetrical in positioning.
  • The holes slowly get bigger and also increase in number.
  • Then, these holes slowly spread to other parts of the body of the fish, like the area around the mouth, eyes, and gills.
  • If the fish doesn’t get treated at this stage, we can see an erosion in the lateral line of the fish.
  • As the disease progresses, we can see stringy mucous coming out of the wounds. This substance contains the larvae of the Hexamita parasite.
  • The fish loses appetite at this stage and stops eating food.
  • The fish also become thin and weak.

Hole in the Head Fish Disease – Treatment

The treatment of the Hole in the head fish disease needs a multi-pronged approach. Since a combination of factors is responsible for causing the disease, the Hole in the head fish disease treatment process needs a multi-step approach. The following steps will help treat the disease and improve the fish’s overall health.


The first crucial step in the Hole in the head fish disease treatment is medication to contain and kill the Hexamita parasite. Aquarium owners can add the Hole in the head fish disease medicine called Metronidazole to the aquarium water. They can add the medication to the fish food and feed it to the fish. 

Fish owners looking to buy Metronidazole online can opt for the API General Cure product. This brand of medication works in eliminating a wide variety of parasitic diseases in freshwater fishes.

If fishes exhibit symptoms of secondary infections, they should be treated with antibiotics such as Furan and Kanacyn. Again, API General Cure available online can cure secondary infections caused due to the Hole in the head fish disease.

Aquarium Salt

The next important step is to add aquarium salt for Hole in the head disease. This is an effective treatment to contain the spread of the disease.

Aquarium owners may have a question – Will salt cure the Hole in the head disease? The answer lies in the advantages that aquarium salt provides to fishes.

  • Aquarium salt is a natural product, and it is obtained from seawater.
  • This salt is an excellent source of electrolytes.
  • The electrolytes will fill the nutrition deficit in the aquarium water, thereby improving the overall health of the fish.
  • The electrolytes will also help with quick disease recovery from the Hole in the head disease.
  • Aquarium salt can also be added to new aquariums and at every water change.

API aquarium salt and Instant Ocean are a couple of commonly used aquarium salt brands available online.


The next important step is to make the necessary changes in the fish’s diet to ensure proper nutrition. The aquarium owners should ensure that any nutritional imbalances are corrected. This will improve the overall health and resistance levels of the fish, giving them enough energy to fight the disease. They can add fish food flakes that are rich in vitamins and minerals to the fish diet. 

Frequent water changes

Once the aquarium owner has identified that a fish is showing the first symptom of the fish head disease, they should ensure that the water in the aquarium is changed frequently. This will ensure mineral and vitamin balance in the water. It will also remove any impurities like nitrites and ammonia. Water changes will also remove parasitic larvae that are present in the water, thus preventing the disease from spreading further.

Frequent aquarium cleanings

It is also essential to clean the tank frequently. This will ensure proper hygiene for the fish in the tank and reduce stress on the fishes.

Isolation of the infected fish

If the aquarium contains some fish, the owner has to separate the infected fish from the rest of the healthy fishes to contain the spread of the disease. Infected fishes that are in the progressive stage of the disease can release parasitic larvae from the holes formed on their bodies. This can affect the other healthy fishes in the aquarium or the pond.

Removal of Chemical Filtration

Any chemical filtration has to be removed since chemical filtration can increase the amount of active carbon in the water. This will adversely affect the condition of the fish.

Install proper filtration systems

Aquarium owners should install the correct filtration systems that can maintain proper levels of all minerals and vitamins in the aquarium water. The filtration systems should also remove any toxins present in the water.

If the aquarium owners can stick to the above steps, they will be successful in containing the disease.

Hole in the Head Fish Disease – Prevention

We all know that prevention is better than cure. A few maintenance procedures done regularly will ensure that the fish doesn’t get affected by the disease in the first place.

  • Aquarium owners should ensure that the aquarium is regularly cleaned and well maintained.
  • Change the water in the aquarium regularly
  • Run regular tests on the water to check for nutrient balance and the presence of toxins.
  • They should add aquarium salt to the water each time the tank is cleaned, and water is changed.
  • The owners shouldn’t put too many fish in one aquarium. 
  • They should provide enough resources for all the fishes in the aquarium.
  • The owners should regularly test filtration systems periodically and replace them when needed.
  • They should check the fish regularly to make sure that the fish look healthy and active at all times.

The Hole in the head fish disease is contagious and can be fatal. The disease can cause huge losses to the aquarium owners. The aquarium owners should be alert to any changes in the appearance of fishes. They should be able to ensure a constant supply of nutritious food to fishes. Maintaining a hygienic and healthy environment in the aquariums will go a long way in ensuring that fishes stay healthy at all times.

To know more about different Saltwater and Freshwater Aquarium Fish Diseases, click this article “Aquarium Fish Diseases: Causes, Symptoms, and Treatments“.