Large white nodule on rainbow shark

[Conchonius]

Have you tested your water?

Yes

If yes, what is your ammonia?

0

If yes, what is your nitrite?

0

If yes, what is your nitrate?

<10 ppm

If I did not test my water...

...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.

Do you do water changes?

Yes

What percentage of water do you change?

21-30%

How frequently do you change your water?

Every week

If I do not change my water...

...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.

This rainbow shark recently developed a large white cyst around its nares. The fish is still active and feeding, other fish in the tank do not show similar growths.

The tank is 200L/55g, tankmates are mainly cories and mid-size (~10 cm/4") plecos. For now, I've done a WC and am increasing WC frequency from 30% weekly to twice a week.

The growth was very rapid, which makes me think something bacterial or fungal (e.g. Saprolegnia?), but it also matches lymphocystis nodules in appearance. I've an 80L/20g spare tank to use as quarantine, as well as methylene blue and Sera Omnipur (malachite green and acridine derivatives as active ingredients) on hand, but if it's a viral cyst I'd rather not stress the animal by moving it around.

I'd appreciate any advice on ID and treatment regimen.

 

[kno4te]

Could be a tumor. Would monitor for growth. If it’s acting normal then I’d leave alone. I doubt if it’s worth it putting a needle in it and get a proper exam by a vet. Sorry….no good answer from me.

 

[Conchonius]

Could be a tumor. Would monitor for growth. If it’s acting normal then I’d leave alone. I doubt if it’s worth it putting a needle in it and get a proper exam by a vet. Sorry….no good answer from me.

Thank you, will do so. I do have a microscope at work, so if the situation deteriorates I can take a smear myself and try to figure out what it is.

I noticed no lethargic behavior this morning either. Rainbow sharks are boisterous for their size, so it tends to boss the cories around during feeding. As long as that continues, the fish's probably got some fight left in it.