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Dr. B.
Dr. B., Veterinarian
Category: Pet
Satisfied Customers: 16155
Experience:  I am a small animal veterinarian and am happy to discuss any concerns & questions you have on any species.
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Hi again,

So, I have had a wee peek at the photos and do have one question about them.
From the photos, it does look like the original white ulcerative tissue has healed back to the level of the rest of the tissue? Is that what you are seeing and is that what the black is sitting on?

As well, can you tell me if you did check ammonia levels along with the others?

Has he been rubbing his head at all or flashing around in the water?
Customer: replied 3 years ago.

Actually, the black seems to be under a thin layer of skin. I will take a water sample to the pet store to check ammonia.


He's not rubbing his head nor splashing. Just acting like his normal, every day, self.

Thanks again for the further information.

If you can have the ammonia checked by the pet store, that would be ideal. The reason why we just want to rule it out and make sure it is not an issue is because chronic ammonia exposure is known to cause black lesions on fish (that often don't change the texture of their skin/scales). If the ammonia is high, then obviously further water changes and ammonia blocking therapy would be indicated.

If the ammonia is normal, then we can put that lower on our list and focus on the other concerns we'd have for this discoloration. If this is a spreading discoloration under a thin layer of tissue, then we'd have to concerned about secondary bacterial or fungal disease. Typically, bacterial infiltration (+/- ulceration) will be due to a water bacteria called Aeromonas. This agent can be treated with erthyromycin but we do occasionally see strains that are not sensitive to this drug. If you treat and see no change, then you may have to simultaneously treat with minocycline (Maracyn2) to clear our this type of bacterial infection. (Though if you find it not settling, then consider also adding in an anti-fungal agent to cover all bases).

If there appears to be any open areas of the lesion, then we use a bit of aquarium salt to support him as well (to address the bacterial infiltration and to encourage his slime coat). In this case, we'd consider using a 0.1% salt concentration, which would be one teaspoon per gallon.When adding the salt, we want to pre-dissolve the salt in tank water before adding and then add it slowly into a high water flow area of the pond.

Otherwise, it is possible to sometimes see the lesion become discolored when the underlying tissue is not getting adequate blood flow. This is not uncommon with viral induced growths but it is possible that the scar tissue may not being getting adequate blood supply after the virus damaged that area. In those cases, we may see it spread without responding to our treatments until he sloughs the tissue again. When this happens, we tend to just have to treat with prophylactic antibiotics to keep infection away until the tissue heals. But hopefully this one will not be the case for this wee lad.

So, do get the ammonia checked to make sure we can rule that out in this situation. Otherwise it sounds like you are on the right track with treatment. If the lesion doesn't show improvement in the next few days, then consider combination treating with Maracyn2 and covering your fungal bases. Hopefully, we will see the lesion settle for him.

All the best,
Dr. B.
Customer: replied 3 years ago.

Thanks. Had the water checked and the ammonia level was, in the words of the person that checked it - "perfect".


Should we change to Maracyn2 right away? There's another one called Maracyn Plus, but it doesn't seem to have minocycline as the main ingredient.


Should we do the salt treatment right away, or wait? Also, it should be marine salt from the pet store, correct?


Thanks a lot Doctor.

Hi again,

I am glad we can rule out the ammonia as our culprit for this lesion since water parameter issues can be a nightmare to steady when they are amiss. Since its not typically practical to culture lesions in fish (due to time/costs/limited labs/etc), it would be fine to combination treat if you wish. It will allow you to cover against any resistant strains of aeromonas that may be present. Alternatively, you could use Maracyn plus (Sulfadimidine and Trimethoprin) but we wouldn't tend to mix it with Maracyn.

In regards XXXXX XXXXX standard non-iodized aquarium salt would be fine for treating him.

All the best,
Dr. B.
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