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Anna, Pet Expert/Biologist
Category: Pet
Satisfied Customers: 11066
Experience:  40 yrs.: herps, pocket pets, rabbits, poultry, dogs, horses. Biology degree. Vet assistant.
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Oscar has strange white discoloration

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I have an Oscar breed fish that has some strange white discoloration on his tail. I have pictures of it. Could you look at this and tell me what it could be and how to treat it? There is not a vet in this area that treats fish.


I'm sorry to hear your fish is having a problem. I looked at the pictures, but it's difficult to see certain things in them.

Are the white areas raised at all, or are they flush with the tail?

Has Carl been rubbing against objects in the tank?

Are his appetite and behavior normal?

Did the white area appear suddenly or develop gradually?

I have access to some aquatic vet directories. If you'll give me your state, I can check for vets.

Thank you.

Customer: replied 3 years ago.

The area in question is white. The area where the base of his tail fin meets his body is normally orange and black. In the pictures, if you notice he is white/fuzzy in that area now. I can best explain it as it looks like he either has a fuzzy fungus (or something) or his slime coat is peeling in that area (looks like a persons skin when it peels after a sunburn) I can't see his scales in the affected area maybe they are gone? To answer you questions directly...


1.) They look a little bumpy and are peeling little bit at the joint of his tail fin and body on the left side only.


2.) No he has not been rubbing on anything in the tank.


3.) His behavior has been normal, but the past 2 days he has not eaten, but this morning he ate the food then immediately spit it out, as of about 15 minutes ago he ate his food for the first time in a few days.


4.) Best I've noticed the area appeared suddenly (I just noticed it today).

Thank you for getting back to me. When I looked at the photos, my first thought was fungus, and what you've described definitely sounds like fungus. It could be more complicated because the peeling effect is often a sign of a bacterial infection, so he may have both. Bacterial infections are opportunistic and often attack a fish that has a compromised immune system caused by another disease. There is also columnaris, which is a bacterial infection that looks like fungus.

If you have a hospital tank, it would be best to isolate the fish there for treatment. If that isn't possible, you'll need to medicate the whole tank, which subjects healthy fish to medicine they don't need. Sometimes there is no choice. Usually we start with a mild treatment. Aquarium salt is recommended for early fungal and bacterial infections. Add one teaspoon per gallon of water. If that doesn't quickly result in an improvement, you'll need to go to a stronger medication. Antibiotics, such as Acriflavine, Furan, and Terramycin are effective against columnaris and other bacterial infections. It is safe to use them the same time as salt. They are found in many of the common fish medications sold in pet stores. An alternative approach is to use both Melafix and Pimafix to treat both fungal and bacterial infections at the same time. These two are also available in most pet stores. You'll have to decide which approach you are most comfortable with.

If you have more questions, let me know by clicking on REPLY. I hope Carl will reach a full recovery.

Anna and 3 other Pet Specialists are ready to help you


Customer: replied 3 years ago.

Thanks for the reply. I am trying a salt dose right now ever since we spoke. I am giving him a 3/4 dose of salt, since I read that my 2 Plecos are sensitive to salt. I also have been doing 10% water changes everyday in case I had some water quality issues. The spot on his tail hasn't got any worse. I would say that it is either the same or a little better.

Thank you for the update. That's good news that the spot hasn't gotten worse. I hope it continues to improve.


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