How to Treat Hole-in-the-Head Disease in Aquarium Fish

Hole-in-the-head (HITH) disease is known by many names — such as hole-in-head, lateral line disease, and head and lateral line erosion (HLLE). None of these are official disease names, but rather, they are descriptors of a visual symptom. In general, they describe any ailment that causes holes, pits, or lesions around a fish’s head, face, and/or lateral line (i.e., the horizontal line of pores running down the side of a fish’s body that is used to sense pressure and movement in the water). In the most severe cases, deep ulcers with bleeding may develop. We have seen this ailment occur in cichlids, goldfish, koi, and even betta fish.

Oscar cichlid with pits in the forehead region

What Causes Hole-in-the-Head Disease?

HITH disease is often attributed to protozoan parasites, such as those in the Hexamita and Spironucleus genera, which are commonly found in the digestive tract but can grow out of control if the fish has a weakened immune system. In practice, fish vets have found that several different types of parasites and bacteria can cause these symptoms. The reason why it can be difficult to find the exact root cause is because the open wounds on the head allow all sorts of pathogens to enter the fish’s body, which means multiple infections may be wreaking havoc at the same time.

Sometimes the parasites or pathogens come from an external source and may be introduced by a new fish that was already sick, so make sure to quarantine all new animals before adding them to your home aquarium. In fact, feeder fish can serve as disease carriers, which is why many monster fish keepers recommend raising your own feeders if your pet requires a live food diet. Plus, an infection can quickly spread from a diseased tank to a healthy one if you accidentally use the same aquarium siphon or move over a decoration.

Feeder fish can carry diseases and infect your tanks at home if they’re not quarantined beforehand.

In other cases, these microorganisms may normally exist in small, harmless quantities within the fish’s body but can bloom into a serious infection if the opportunity presents itself. HITH disease is commonly seen in environments with poor water quality, such as when the ammonia and nitrite levels are above 0 ppm when measured with an ammonia test strip and multi-test strip. It can also be caused by nutrient deficiencies. When a fish is fed the same kind of food every single day, it won’t contain all the key nutrients, vitamins, and minerals needed for optimal health. It would be like a human eating pepperoni pizza every day and never including any fruits or vegetables in his or her diet. Plus, check to see if the fish food is expired or spoiled from exposure to moisture. The reality is that any number of stress factors — such as bullying, cold temperatures, or huge swings in pH — can cause a fish’s immunity to be weaker than normal and introduce potential health issues.

How Do I Treat Hole-in-the-Head Disease?

The first step is to eliminate any sources of stress. Immediately check the water parameters with multi-test strips and see if the water quality needs to be improved. This may include increasing your water change frequency, removing some fish from the tank, or feeding less if excess food isn’t getting eaten. Increasing the number of live plants in the aquarium can also help keep ammonia, nitrite, and nitrate in check since they actively consume those waste chemicals as food. Fast-growing plants like Pogostemon stellatus tend to consume toxic waste chemicals at a quicker rate, but if you have large fish that like to nibble on plants, try sticking some pothos in the water and protecting the roots in a hanging basket if needed.

Use test strips to measure the aquarium water quality, and increase the tank maintenance frequency if needed.

Consider changing up your fish’s diet as well. If your betta fish was only fed betta pellets every day, then add some frozen bloodworms, freeze-dried brine shrimp, fish flakes, and baby brine shrimp for more variety. Rotate through the different foods each day of the week to ensure that they have enough nutritional variety in their meal plan.

In terms of medications, we recommend starting with a broad-spectrum antiparasitic medication like Fritz ParaCleanse, which contains both metronidazole and praziquantel as its active ingredients. It is safe for fish, plants, and invertebrates in our experience. Remove any activated carbon or other chemical filtration, and keep the filtration or an air stone running so there is plenty of oxygen going into the tank. Follow the manufacturer’s instructions on the package for the 5-day treatment plan. Some parasites lay eggs that are not affected by the medication, so you may need to wait 2 weeks for them to hatch and then repeat the 5-day treatment to ensure everything is gone. If there are no signs of improvement, consider using a copper-based fish medicine, starting at a low concentration of 1 drop per gallon to see if the fish will tolerate it. In general, copper is very hard on fish and can be lethal to invertebrates like shrimp and snails.

Fritz ParaCleanse is a broad-spectrum antiparasitic fish medicine that is used to treat hole-in-the-head disease.

The medications we suggested are over-the-counter solutions that are available to aquarium hobbyists in the United States. However, since HITH disease can be caused by many different types of parasites and bacteria, a fish veterinarian is your best bet for finding the root cause of the disease if you have the money to spend. They will be able to take scrapings of the lesions and fecal samples, grow cultures if needed, and examine them under a microscope to make sure the fish gets the exact medicine to treat the problem. Unfortunately, there is no guarantee that the fish will recover, depending on the severity of the disease and how far it has progressed. If the illness was caught early enough and the stress factors are eliminated, the holes will heal over. The indentations will become shallower over time, but the new skin may grow back a little discolored, either temporarily or permanently.

For more information on different fish diseases, check out our collection of blog articles to find the best treatment for your ailing pet.