Posted by Coersum on February 15, 2003 at 03:20:40:

Hi,
I have a black Male molly that I put in a new 10 Gal tank to cycle it. He was fine when in the main (30 gal) tank, but a week after putting him in the 10Gal, I saw one of his side fin has a hole with a fine white line around the hole.
Since he moves too fast and couldn't take a picture, I did my best to reproduce how it looks. Any idea what could have caused it and how to treat him ?
I had him when cycling my 30 gal with other fish and he never had a problem.
Thank you for any help.
David