Oscar fish is a messy fish which easy pollute the water in aquarium. Performing a water changes of 20 -30% every week is needed and installing a good filtration system is required. There still need to put a lot of effort to keep the Oscar fish diseases away.

There are few common diseases infected the Oscar fish and cost the fish lives. Here are the common diseases you should pay attention of that list in this post. This common diseases are caused by poor water quality and overcrowded in the Oscar fish aquarium.

There no need to worry, here are the guide on treating the fish with the suitable medication to keep them healthy as usual. Preventing the diseases infected the fish are always the important part because there is quotes of “prevention is better than cure”.

Hole In The Head

Hole In The Head Disease

Hole In The Head Disease

This one of parasite infected diseases which often infected Oscar fish and also one of the common Oscar fish diseases. You may found white sores around the fish head with a large hole. The fish also will show less appetite and mucous trailing from the holes.

As you see the fish have this sign and symptom you need to treat them because it could lead the fish to death if not treated.


  • Add malachite green and formalin into the aquarium to treat the fish. Leave the aquarium for 24 hour and perform a 35% of water changes and monitor the fish for a week.
  • Mix metronidazole into the fish flakes and feed the fish. Treat the fish for 5-10 days and the fish will go back to normal and healthy.

This diseases infected the fish because of overcrowded, imbalance mineral, poor water quality and lack of nutrition. By preventing the cause that listed on top, the fish are free from the diseases.

Fin And Tail Rot

Fin And Tail Rot Disease

Fin And Tail Rot From Oscarfish.com

This is a bacterial infection that you need to pay attention on the fish fin and tail. The fin and tail of the fish will show sign of decay and discoloration which the tissues is eaten by pathogenic bacteria. The fish will show the symptom of slimy or milk appearance to fin and the fish have no appetite.

The fish also will spend more time on the surface. This is a picture which I get from forum in Oscarfish.com.


  • Treat the fish with this antibiotic when the fish showing the sign and symptom fin rot diseases. Treat them with Tetracycline, Oxytetracycline and Chlorampheniol by referring the dosage of the medication.

Preform a 30% of water change in the aquarium and add aquarium salt. You can use this measurement by adding 1 teaspoon of salt for 10 gallon water and mix it until dilute before adding into the fish tank. On the 6th day, reverse the treatment and perform water changes for another 5 days.

Repeat the entire treatment by using salt on the 11th day. Monitor the fish for 30 days and repeat the entire treatment again if the infection is remain.

This diseases are lead from low oxygen level, poor water quality and stress from poor environment. Preventing the Oscar fish from this diseases, make sure the fish are living in a suitable environment.

Ich Disease

Ich Disease

Ich Disease

This is protozoan infection which you need to pay attention too. This is also one of the common Oscar fish diseases you may face. The fish will show the symptom of white spot on the gills, reddening on it fins and the fish sinking on the bottom of the aquarium.

The fish will also keep on gyrating around the aquarium wall or rock. This diseases can cause fatal to the fish and treating the fish as soon as you notice the sign of Ich.


  • Treat the fish with malachite green, copper sulfate, or formalin by reading the instruction on the medication. Increase the water temperature during the treatment because the higher temperature will speed up the life cycle of the Ich diseases and decrease the time required for the treatment. Before using the medication, read the instruction of the treatment because some of the medication may kill the live plant in the aquarium.

Ich diseases appear in the aquarium because of new live plant or fishes are bought into the aquarium without quarantines them for at least a week. Preventing the diseases infect Oscar fish, quarantine the new fish and live plant at least a week to monitor before introduce into Oscar fish aquarium.

Popeye Disease

Popeye Disease

Popeye Disease

The eye of the fish are swallowing and popping up. The fish will show a cloudy appearance to the eye either with both eyes and single eye. This disease are pretty straight forward but treating them would be a challenges.

Popeye disease are mainly caused by poor water condition.


  • As we mention before, this disease are caused by poor water condition which correcting the water quality and perform a water 30% of water change. Add up a teaspoon of aquariums salt for 5 gallon water.
  • If you keeping the fish together with a different freshwater, you may move the fish to a different aquarium. The fish may get injured by other fish in the same aquarium.
  • Treat the fish with antibiotic with Maracyn and Maracyn II. Follow the instruction of the medication to prevent overdose.

Preventing the fish infected by this disease, keep the water condition and quality in well maintain and care.

Dropsy Disease

Dropsy Diseases


Dropsy disease are mainly cause by overfeeding and also one deadliest Oscar fish diseases you should aware off. You may notice the fish with a bloated appearance on it body and the fish are having trouble to swim.


  • Treating dropsy by perform 30% water changes and increase water temperature by 1 to 2 degree Celsius. Feed the fish with small pieces of slight cook peas. Do not feed fish flakes or live food for the fish.
  • If the fish condition are not improving, it may be serious medical problem such as organ damage, intestinal blockage or tumors. A home treatment not often success and most fishes dies. It is recommended to treat the fish at any local veterinarian which can improve the situation.

Prevent the fish infected with this disease, it is recommend to feed the fish with balance diet to keep the fish healthy.

My Conclusion

After reading this post about Oscar fish diseases, the best to keep the fish healthy is preventing the fish sick. Make sure test the water in the aquarium frequently and make sure the ammonia and nitrates level are in acceptable level. Always quarantine the fish or live plant for at least 2 week before introduce to the Oscar fish aquarium.

Monitor the water temperature of the aquarium by installing a heater together with thermometer. Last but not least, do not overcrowd the aquarium because it would cause stress to fish in the aquarium and make sure the filtration system are good to maintain the water quality.

After reading the post of mine about “Oscar fish diseases”, you able to treat the fish and keep them harmless from disease. If you have comment, feel free to leave a comment here. Cheers!