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Hello everyone. I have a school of nine healthy Corydoras Sterbai. One of them, Chessie, developed a sort of pimple a couple of months ago. It starts out about the size of a large grain of sand and then grows bigger and bigger until it kind of sloughs off. Then the cycle begins again. Other then the pimple, she is healthy, alert and eager as are the other 8 Sterbai. Since all the other fish and Sterbai are healthy, I'm not going to post water quality measurements. Chessie is the only fish with the pimple, so its not contagious. Its definitely not a parasite and isn't fuzzy like a fungus. Look at the pictures espically the shot of Chessie next to an unaffected Sterbai. Can someone please tell me what this is and if its possible to treat. I want to help her. Thank you! -Mike

Wow, never seen anything like that before.

Good photos.

If I were you, I would try isolating this fish and waiting for the yellow object to fall off, then examine it in a microscope or under a magnifying glass. Maybe you could see some detail if it's a parasite.
I'm not saying it is a parasite, but that is something I'd consider.

Good luck,
Eric

https://www.planetcatfish.com/forum/vie ... 47#p309518

this thread is about something similar (its a red bump not a yellow one but they meds could help this to) , if it gets worse or doesn't fall off then you could try what this guy did.

Right after I posted these pics the yellow granule started separating and fell off. I couldn't retrieve it. Now she just has a white raw spot. Typically, another eruption will start growing soon. Chessie was an aggressive digger, until she got a sore nose. I'm wondering if she got a splinter or shard of something stuck in her nose and this is some sort of granuloma process to get rid of it? Here is a fresh pic.

After about 6 weeks and several cycles of enlarging and sloughing off Chessie's pimple seems to have stabilized into a sort of callus. Never treated with anything. And none of the other fish ever fell ill. I can't use sand so those beautiful barbells are on a gravel substrate!