Thank you very much for answers. I'm cleaning the tank as advised. My
Goldies are still happy, but affected areas of skin are bigger. Here
are better images:
http://img87.imageshack.us/my.php?image=001cg3.jpg
http://img215.imageshack.us/img215/6774/003axy9.jpg
A guy from local Pet Store advised me to use Fungus Clear (http://
www.junglelabs.com/pages/details.asp?item=TB630) to treat water in
tank. Re antibiotic food, I'm in Canada and can't order from
www.goldfishconnection.com, my ZIP is not valid :-)