Oscar Fish & Hole in the Head (HITH): Symptoms & Treatment

Oscar with Hole in the Head Disease
Oscar with Hole in the Head Disease

Note: While this article is intended to provide helpful and accurate information, it is not intended to replace professional veterinary advice.

Oscar Fish & Hole in the Head Disease (HITH)

Hole in the Head Disease (HITH), is a disease that commonly affects Oscar fish and other cichlid species. Hole in the Head Disease (HITH) is also known as Freshwater Head and Lateral Line Erosion (FHLLE).

Since Oscar fish are susceptible to this disease, it is important to have an understanding of this disease, even if your Oscar does not have it. Of course, if you are already observing symptoms of this disease, it would be critical to have a thorough understanding of this disease.

This guide will cover the symptoms, treatments, causes, and prevention of Hole in the Head Disease in Oscar fish.


The most notable symptom of Hole in the Head Disease is the appearance of holes on the head of the fish, as the name suggests. As the disease progresses, these holes become larger and secondary bacterial and fungal infections may develop. Lesions can also appear along the lateral line of the fish and might start spreading to the mouth area and could even appear near the gills and eyes.

Here are the symptoms of Hole in the Head disease in Oscar fish:

  • Pitted Lesions: The most recognizable symptom is the appearance of small, pitted lesions or holes on the Oscar fish’s forehead and along the lateral line.
  • Lethargy: An Oscar fish with the disease may seem less active, spending more time at the bottom or hiding in the aquarium.
  • Appetite Loss: Affected Oscar fish might lose interest in food, leading to noticeable weight loss over time.
  • Stringy Feces: Oscar fish suffering from the disease may produce white, slimy, string-like feces, indicating internal complications.
  • Cloudy Eyes: In advanced stages, the Oscar fish’s eyes might turn cloudy, signaling potential infections or other related issues.
  • Ragged Fins: The Oscar fish may also show signs of ragged or deteriorating fins.
  • Slime Coat Shedding: Increased mucus or slime production can be observed, with the Oscar fish occasionally shedding its slime coat.
  • Mucous Trailing from Holes: You might notice that mucus will come out of the wounds as well. Stringy mucus will sometimes be seen trailing the lesions and these strings might look like worms as the fish moves in the water.


While the exact cause of Hole in the Head Disease in Oscar fish remains unknown, there are several factors that may contribute to this disease.

Here are possible causes of Hole in the Head Disease in Oscar fish:

  • Hexamita Infection: The Hexamita parasite is a common cause of Hole in the Head Disease. This microscopic parasite lives in the water and can infect fish, causing inflammation and damage to the brain and spinal cord.
  • Unstable Nutritional Value: Nutritional imbalances in the tank can lead to this disease. A lack of oxygen and nutrients can cause deformities in the fish’s brain.
  • Unfavorable Environment: Stressful environments and poor water quality can also contribute to the development of this disease. Temperature fluctuations can cause stress in the fish, making Oscars more susceptible to hole in the head disease.
  • High Bacterial Counts: High bacterial counts in the water can compromise the immune system of the fish, leading to diseases like Hexamita or TB.
  • Stress: High levels of stress can result in weakened immune systems, making them more susceptible to Hole in the Head Disease
  • Activated Carbon: One theory suggests that the use of too much activated carbon in aquarium filtration systems might be linked to the Hole in the Head Disease. Some aquarists believe that the carbon may remove some of the beneficial minerals found in the water, leading to an increased incidence in the disease. A study conducted on aquarium fishes at the Toledo Zoo deduced that the dust produced by activated carbons might be responsible for triggering Hole in the Head Disease in freshwater or marine fishes. However, it’s important to note that these are just theories and more research is needed to confirm these findings.
  • Stray Voltage: Malfunctioning electrical appliances, such as heaters, may have electricity leaking into the water. This may cause Hole in the Head Disease. However, this is more of a concern for saltwater fish. Since Oscars are freshwater fish, this is usually considered to be less of a concern.


There are multiple treatment options for Oscars with Hole in the Head Disease. Some are more effective than others, and the treatment usually consists of taking a multi-faceted approach.

Here are the treatment options for Oscars with hole in the head disease:

  • Changing Diet: A poor-quality diet or one lacking essential nutrients might make Oscar fish more susceptible to the disease. Therefore, a balanced diet can help boost the fish’s immune system and overall health.
  • Isolating Affected Fish: Isolating the infected fish can prevent the disease from spreading to other fish in the tank. This is particularly important if the disease is suspected to be caused by parasites, such as the Hexamita parasite. Some treatments for Hole in the Head disease may involve medications that could be harmful to other fish or absorbed by carbon filters. Isolating the infected fish allows for a more controlled and effective treatment environment.
  • Reducing Use of Activated Charcoal: Too much activated charcoal could be a cause of Hold in the Head Disease. Therefore, reducing it could help.
  • Increase Water Change: Poor water conditions are believed to be a significant contributing factor to the disease. Therefore, frequent water changes to maintain good water conditions would help.
  • Increase Aeration: Proper aeration is important in preventing the disease. Therefore, it may help with treating the disease as well.
  • Aquarium Salt: Salt can be used as part of the treatment process. Adding small doses of special aquarium salt to the water can help with treatment. For instance, you can add one tablespoonful of the special aquarium salt to 5-10 gallons (18.93-37.85 liters) of water. Another option is adding 1-2 teaspoons of Epsom salt per 10 gallons of water. However, it’s important to note that while salt can help, it may or may not be a complete cure.
  • Seachem MetroPlex: Seachem MetroPlex contains the active ingredient Metronidazole. It is effective in treating various bacterial diseases including Hexamita (believed to be a significant contributor to Hole in the Head Disease).
  • Other Medications: There are various other medications such as Becaplermin, Copper sulfate, Formalin (formaldehyde), Praziquantel, Dimetridazole, Maracyn, Kanacyn, and Furan that may help treat Hole in the Head Disease. However, many of these medications should be administered under the supervision of professionals such as a veterinarian. In fact, many of these medications are not available without a prescription. If you decide to use the medication to treat the disease, it’s important to read product labels carefully and follow dosage instructions closely.


Understanding how to prevent Hole in the Head Disease is important, because prevention is always better than cure.

Here are some ways of preventing Hole in the Head Disease in Oscar fish:

  • Maintain Water Quality: Keeping the water clean with stable parameters is crucial. This includes monitoring water conditions to prevent ammonia and nitrite buildup.
  • Prevent Temperature Fluctuations: Sudden changes in temperature can stress the fish and make them more susceptible to diseases.
  • Nutritious Diet: Feed your Oscar fish a varied and nutritious diet. Nutritional imbalances can lead to this disease.
  • Minimize Stress: Changes in their environment, such as a new person in the home, or a new pet inside the aquarium, can stress the fish and lead to diseases.
  • Quarantine New Fish: New fish should be quarantined before being introduced to the tank to prevent the spread of diseases.

Is Hole in the Head Disease Fatal for Oscar Fish?

Hole in the Head Disease can be fatal for Oscar Fish if left untreated. If left untreated, the lesions on the fish may worsen, and along with other symptoms, the fish may lose its appetite and cease eating altogether. Eventually, this may lead to death. If Hole in the Head Disease is suspected, it is important to properly diagnose and treat the fish right away. This will give your Oscar the best chance of survival.

Is Hole in the Head Disease Contagious?

Hole in the Head Disease may be contagious to other fish.

When one Oscar develops Hole in the Head Disease, other Oscars in the same tank often develop the same symptoms. Of course, this may be due to the fact that all fish in the same tank are exposed to the same poor aquarium conditions and nutrition.

With that said, according to a resource by University of Florida, Hexamita is believed to be transmitted through water from contaminated fecal material. Since Hexamita is widely considered to be the common cause of hole in the head disease, it is best to isolate fish with Hole in the Head Disease as a precautionary measure. In addition, isolation would be good when treating the fish as well.

Leave a Comment

Your email address will not be published. Required fields are marked *