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Home > Fish > Hole-in-the-Head Disease in Fish: Signs, Causes, Care & Prevention

Hole-in-the-Head Disease in Fish: Signs, Causes, Care & Prevention

Hole in the head disease

Oftentimes, people underestimate how much work goes into caring for fish. There are water parameters, temperatures, and appropriate plants and décor that must be considered. Sometimes, you may even run into a situation where you have a sick or injured fish and you’re unsure how to care for them.

One disease in fish that is often mistaken for an injury is hole-in-the-head disease, which can be deadly if left untreated. Even if treated, if the symptoms have progressed too far, it can be difficult to cure a fish of this disease. Here’s what you need to know about it.


What Is Hole-in-the-Head Disease?

Hole-in-the-Head (HITH) disease is exactly what it sounds like: a condition that causes a hole in the head. There’s a lot more to it than that, though. This disease is also sometimes referred to as head and lateral line erosion in fish, which would indicate that it impacts far more than just the head of the fish.

This unfortunate disease is not a disease at all, but a parasitic infection caused by the Hexamita parasite, which is why it’s typically referred to as Hexamitiasis in scientific literature. These parasites are too small to see with the naked eye, but the damage they can cause is unmistakable. There are multiple species of Hexamita, with some species naturally residing in the intestines of fish. These parasites are usually of no concern until the fish is otherwise stressed or sick.

HITH can impact both freshwater and saltwater fish, making it one of the very few parasites that can thrive in both types of environments. Perciformes, or perch-like fishes, seem to be at the greatest risk, which would include all varieties of Cichlids and Bettas. In fact, this diverse group of fish accounts for around 40% of all bony fish species in the world.

It should be noted that there are some people who believe that HITH is separate from Hexamitiasis, claiming that the external symptoms are caused by a different pathogen, while the internal symptoms are caused by a Hexamita species.

red flower horn with hole in the head disease
Image Credit: Platu Studio, Shutterstock


What Are the Signs of Hole-in-the-Head Disease?

  • Holes and wounds in the head or face
  • Holes and wounds along the lateral line
  • White, stringy feces
  • Yellow, stringy feces
  • Bloating or dropsy
  • Hollowed abdomen appearance
  • Weight loss without appetite loss
  • Inappetence
  • Spitting out food
  • Constipation

What Are the Causes of Hole-in-the-Head Disease?

Although we know that HITH is caused by a parasitic infection, it’s important to understand what allows it to take hold. This issue does not impact healthy, happy fish. The primary cause of this disease is stress, but there are multiple things that can cause stress for your fish.

Poor water quality is one of the top causes of any disease in fish. It’s essential to the health and well-being of your fish that you maintain routine water changes and check water parameters to ensure high water quality is being maintained.

Fish can also be stressed by temperature extremes, especially temperatures that are too high. Low temperatures may cause fish to enter a semi-hibernation state called torpor, during which their metabolic function and activity level drops significantly. This state is not healthy for many captive fish.

Keeping fish in a tank that is too small for them or overstocking the tank can also lead to significant stress for your fish. While there are not many truly hard and fast rules about how many fish you can keep in your tank, you should always work to stay within reason when considering the size of your tank and your commitment to performing water changes. The more fish or the larger the fish that you have, the greater the bioload in the tank will be, which will require more water changes than fewer or smaller fish would.

Another major stressor for many fish is bullying within the tank, and fish bullies use much more than mean words. Fish bullies will bite and nip, chase, shove, corner, and endanger the health of other fish. There are a few reasons that bullying may be occurring, and it’s dependent on the tank environment and species of fish. Some fish will show territorial behavior and others may show bullying behaviors during mating attempts, while some species of fish should only be kept in harems, or multiple females with only one male, or with a specific number of fish of the same species to prevent bullying and territorial behaviors.

How Do I Care for a Fish with Hole-in-the-Head Disease?

Your fish will absolutely not heal without pristine water quality, which may mean performing more frequent water changes during the healing process or moving them to a hospital tank. Check your water parameters regularly during the healing process, and it’s preferable to use a liquid test kit as they are often more accurate than strip tests. You should also work to identify the primary stressors within the tank and begin remedying them, keeping in mind that multiple stressors can be occurring in one tank.

Feed your fish a high-quality diet that is appropriate for their species. When healing from an injury or illness, an increase in protein consumption can support healing, so you may need to offer a higher protein food or treat than you typically do. This could be a switch to a higher quality pellet food or the addition of bloodworms or brine shrimp to the daily diet.

If you’ve been able to identify that there is a bully in your tank, then it’s time to take action. Sometimes, a little bit of “time out” in a floating colander or behind a divider may fix the problem. If the behavior is related to breeding, it will likely resolve after breeding has occurred, although some fish will become quite territorial protecting their eggs and young. If you’ve identified that there’s a fish that’s simply being a bully, it might be time to consider moving them to a different tank or rehoming them entirely to protect the other fish in the tank.

Goldfish waiting for food
Image Credit: Kravchuk Olga, Shutterstock


Frequently Asked Questions

Can I treat HITH with antibiotics?

You can try, but it’s generally not recommended. Antibiotics won’t fix the underlying stressors, nor will they kill a parasite. If you suspect your fish may have developed an infection from the wounds or stress, then an antibiotic may be needed. Using antibiotics can be stressful to already stressed fish, and many of them risk killing off the good bacteria within the tank.

What is the lateral line?

The lateral line is part of a system of sensory organs that help your fish sense changes in the water, including movement, pressure, and vibration. It helps them know how to maintain an upright position, warns of predators, and find prey. The lateral line runs in a straight line down both sides of the body from the back of the gills to the tail.

Can my fish have multiple illnesses and infections at the same time?

Yes. Just because your fish has HITH doesn’t mean they don’t also have other problems. Secondary infections are common with poor water quality, especially if your fish has open wounds. Illness also depresses the immune system’s ability to fight new infections, making your fish more susceptible to developing a secondary illness.



Hole-in-the-Head Disease is a frustrating condition that can take time and lots of effort to correct. The best treatment for HITH is preventing it in the first place, but if your fish has developed symptoms, you need to act fast to begin helping your fish heal and eliminate the stressors in the environment. Water quality issues are the most common cause of HITH, as well as other conditions, but there are a variety of factors that can lead to stress and illness for your fish.

Featured Image Credit: Pavaphon Supanantananont, Shutterstock

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