Oscar Fish Diseases, Treatments and Prevention

Oscar fish is one of the famous fish as a pet. People love to see these beautiful species inside an aquarium swimming. They are commonly known as tiger oscarvelvet cichlid, and marble cichlid, in the market. The reason for the popularity of oscar fish is that it responds to the surrounding, swims, and shows its fins when people are around. Some evidence also says that it can distinguish its owner from other people. These beautiful creatures sometimes suffer from diseases so, in this article, today we are going to talk about the most common Oscar Fish Diseases and Treatments. You need to treat these cichlids very quickly to flourish the fish and not spread them to the worse.

common causes of the fish catching diseases preventive measure

  • using poor quality of water in the aquarium,
  • the addition of the contaminated fish,
  • introduction to the contaminated equipment in the aquarium.

The most common diseases the Oscar fish get are Hole In The Head (HITH), ICH(White Spot Disease), Fin and Tail Rot (Columnaris Disease), Popeye Disease, Bloat Or Dropsy, and Septicemia. You can prevent most of the disease with these simple procedures:

  • changing 10% of the water of the tank every week
  • inspecting the tank on a routine basis for any damage and contamination
  • quality testing of water in the tank with water tool kits
  • keeping the balance of water level and maintaining the quality of the environment.

In this article, I will teach you, based on my experience, what kind of diseases do oscar fish get, and what are their treatment and preventive measures. On my ten years-long journeys of Oscar keeping, I lost a lot of fish because of many diseases and silly mistakes; I made by ignoring its symptoms. This article will certainly help you to keep your oscar life span up to fullest.

Prevention is Better Than Cure

As the title says, to prevent your oscar from getting any diseases, you have to make its environment, i.e., water, clean and uncontaminated. The cleansing of the water tank is the most important because it can help us prevent many infections and contamination. Also, another important point is changing the water periodically, which will remove the possible contamination. The Oscars get most of the disease from the contaminated water. The cleaner environment with lots of pebbles, dim light, and places to hide with flowing water could be the perfect condition for the oscar fish to live.

Oscar Fish Diseases, Treatments and Their Prevention

Oscar fish are very pleasing to look but harder to care. Unlike other fish, they require more care, attention, and devotion. The fish tank water should be changed at least every week, if possible, twice a week. These fish are not injury-prone, so we have to make sure they don’t get injured or catch the disease. These fish are large and have a high appetite, which makes it even harder to maintain the fish’s proper care and diet. All the things have to be balanced to get the oscar in your tank in perfect condition. And as these fish mark their territory and quarrel with other fish for the territory, special attention must be given to them for injury or any sort of damage in their body regularly.

I have searched throughout the internet and collected the information about the most common diseases oscar fish can get. I have listed out the diseases, its symptoms, cause, and treatment below.

Hemorrhagic Septicemia

A bacterial infection causes septicemia. The infection happens due to the open wound left out for a long period. As well the ammonium spike in the tank can be the cause of this disease. The excessive amount of ammonia affects the immunity system of the fish and may be exposed to the infection quickly. The oscar fish tends to defend its territory and fight with other fish in the aquarium. This will lead to injury and result in the contamination of the water.


The cause of this disease is a bacterial infection that could occur due to an open or improperly treated wound. Some of the basic causes are :

  • Dirty environment and ornaments.
  • You have a crowded aquarium or pond.
  • High ammonium in the water.
  • Collection of waste on the tank due to overfeeding and other matters


You can treat bacterial infections by applying antibiotics to the wounds and infected areas. To prevent this disease, as soon as the fish gets injured, you must clean tank water, and you should treat the fish with some antibiotics. Doing so will help the fish from getting septicemia.


Some of the prevention measures are as follows :

  • Reducing the crowd
  • Proper cleaning of the tank and its ornaments
  • Use of clean water

Fin and Tail Rot (Columnaris Disease)

Fin and Tail Rot is also another bacterial infection disease. Till now, there are no exact known bacteria that causes this infection, some of the possible candidates bacterial are as follows: Flexibacter spp, Pseudomonas spp, Cytophaga spp, and Flavobacterium columnarae. This disease is common when the fish is exposed to the low quality of water, the crowded environment in the aquarium, and low oxygen state. This infection could also take place from the previous wound or rash.


  • Poor quality of water
  • Crowed Environment
  • From old wound or rash
  • Low oxygen levels
  • Dirty environment


  • Less Appetite
  • A slimy or milky appearance to the body or only to fins
  • Always found in the surface
  • Parts of the fins may fall
  • Blackened or bloody fins
  • Listlessness or lethargy


The treatment of the fin and tail rot of Oscar fish requires medicine, usually antibiotics if the infection is severe, surgery is done to remove the infected portions of the fish. In some cases, the fins grow back. For effective treatment of the fish, you must provide the most detail abnormal behave and probable cause. Some of the antibiotics used to treat the fish are as follows:

  • Chloramphenicol
  • Tetracycline
  • Oxytetracycline

After you finish doing the treatment, I recommend you to change the water in the tank and possibly the environment; if not properly cleaning the environment inside the tank.


  • Use a good filtration system for your tank
  • Keep your water clean
  • Provide a proper oxygen cycle to your fish.

Bloat or Dropsy

Bloat or Dropsy is the condition which is caused by overfeeding and constipation. This is not an actual disease but symptoms to more severe disease. The major change we can find in the fish with the bloat or Dropsy is a swollen abdomen and irregular swimming pattern.


  • Low Immunity
  • Overfeeding
  • Untidy Environment


  • Swollen Abdomen
  • Irregular movement patterns
  • Feces trailing in the back
  • Bloat appearance


The basic way to treat constipation is by providing less food for a while. The basic mantra to treat is to clean the water; it protects and reduces the chances of exposing too many diseases. Some basic treatment measures are:

  • Changing of water in aquarium and pond
  • Withholding of the foods being served
  • Increasing the temperature of the water by 1 or 2 degrees

These steps don’t guarantee the cure because bloat is the symptom of another disease; this could be the cause of different conditions like internal organ damage, tumor, intestinal blockage, or other. After trying these steps, if no improvement is seen, consult a veterinarian.


  • Don’t Overfeed your fish
  • Do a frequent water change.
  • Always quarantine sick/new fish for 3-4 weeks.

Popeye Disease

Popeye medically called as exophthalmia is a condition in the fish where the eyes are swollen and seem popped out of the eyelids. Some fish species like Black Moor goldfish and the Celestial Eye goldfish have the eyes that are popular for their big and bulky eyes. This condition may result from losing your fish eyes.


There are various factors responsible for causing this disease. Oscar fish tends to quarrel with other fish, check for an injury sign if there is a popeye. If there is popeye in only one of the eyes normally, it’s due to fighting with other fish or collision with any object in the aquarium or pond. Some of the major causes are :

  • Poor water condition
  • Bacterial infection
  • Internal damage(kidney failure, Metabolic issue)
  • Level of supersaturation of gas in water


  • Swollen eye
  • Cloudy appearance in the eye
  • Bloodstains in the eye if caused by injury


The treatment of popeye will be different according to the case . If the cause is an injury, you should treat the fish by aquarium salt in the water until the eye returns to its natural state. But if the cause of the disease is bacterial infections, put the fish in quarantine so that the infection doesn’t get spread to other fish and treat the fish with broad-spectrum antibiotic food. If more than one fish is infected, then treat the whole tank with the broad-spectrum antibiotic food.

You should maintain your water, change it regularly, and test it for any infection in a routine period of time. If any abnormal situation happens with popeye, consult a veterinarian.


  • Maintain your water quality
  • Do a frequent water change.

Fungal Infection

Fungal infection is a very common disease among tropical fish. The fungus quickly develops inside the water and around the environment that could be hazardous to the fish. Usually, the fungal infection only affects the internal tissues, the characteristics of appearing of white fluffy substance in the surface of the fish are known as “cotton wool disease” if the condition gets worse, it can turn into gray and red.


  • Poor Water Condition
  • An increasing amount of decomposing organic material
  • The dirty environment inside the aquarium
  • High possibility of injured and old fish due to low immunity


  • Changed skin color normally partially
  • Less activity
  • Rotten fins and gills if severe
  • Gills and mouth covered with mucus


You can cure fungal infections with cleanliness and hygiene. The fungal infection seems to affect more on weak and injured fish, keeping the fish in proper condition prevents fish from catching the fungal infection. Some necessary steps to follow to avoid the fungal infection are :

  • Changing water frequently
  • Testing water quality
  • Water tank and check for any contamination
  • Avoiding decomposing organic material


  • Maintain your water quality
  • Do a regular water change of your tank.
  • If your fish is sick, move it to a hospital tank.

Hole In The Head (HITH) Disease

In the medical term, this disease is called “Hexamita “in a sense; it is caused by flagellate parasite Hexamita. The exact cause of this disease is still unknown, but there are several conditions that could lead to this disease. If you treat the disease in time, the fish can survive.


  • flagellate parasite Hexamita
  • Poor Water condition
  • Unbalance minerals
  • Improper Nutrition
  • Low Immunity


  • Holes in the head
  • Low appetite
  • The pitting-type lesion in the head
  • Mucous trailing from the holes present


The most common treatment for the fish with Hole In The Head is to bath the fish in the antibiotic named metronidazole for six to twelve hours according to the condition and severity of the fish. If the fish is in condition for eating we can feed the metronidazole medicated food flakes to the fish this treatment takes longer than the bath, it takes six to ten days.


  • Maintain your water temperature
  • Keep your water clean.
  • Provide a proper nutritious diet to your fish.
  • Change your 20% of water at least once a week.
  • Quarantine sick fish.

ICH (White Spot Disease)

Ich(White Spot Disease ) is caused by Ichthyophthirius multifiliis, a protozoan parasite. It develops rapidly in warm water. The disease is mainly brought into the aquarium through the addition of new fish, new plants, or foods.


  • Poor Water Condition
  • Fungus
  • Irregular cleaning habit


  • White spots appear on the skin and fins
  • Loss of appetite
  • Higher gill movements
  • Found at the bottom of the aquarium or tank
  • Reddening of fins


ICH, if not treated properly, can lead to the death of the fish and contamination of the disease. There are various treatment procedures and medicine available to treat the disease. They are as follows :

  • Using salt in the water (non-iodized table salt, Kosher salt, or sea salt)
  • Formaldehyde (formalin)
  • Malachite green in the proper amount
  • Victoria green and acriflavine
  • Copper sulfate
  • Increasing the temperature of the water during the treatment phase


  • Always quarantine your new/diseased fish for at least a few weeks.
  • Do a frequent water change.
  • Maintain an ideal temperature.

Disease Prevention

Its always true that prevention is always better than cure. There is various task that can be done to keep the fish healthy and reduce the chances of catching the disease. Some preventive measures are as follows :

  • You should test water levels regularly for the balance of ammonia and nitrates.
  • Cleaning of the water tank, aquarium, and pond regularly.
  • You must Clean the ornaments and equipment properly before and after using them.
  • Feed the proper fish nutrition to your fish.
  • Provide the proper space for the fish in the tank.
  • Change the filter pads and equipment on a regular basis.
  • Quarantine the infected and injured fish and treat them as soon as they get sick.
  • Maintain the water and oxygen temperature.


Oscar fish is one of the most loved and popular pets in the world of fish despite being the native of the subtropical region. The fish need more attention, devotion, and care compared to other fish. You must keep oscar in proper water conditions, nutrition, and minerals. Proper care with the right materials and equipment will make an Oscar fish a delight to watch in action in the aquarium. If any severe condition arises, consult a veterinarian.

If you want to know more about the fish, its behavior, and interesting facts, then you can surf around my website FishKeeping Guide.


Image Credit: https://commons.wikimedia.org/wiki/File:Tiger_Oscar_Fish.jpg

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