Question
Hello pond ethusiests!!! I have a pond with koi and goldfish one fish i noticed
one of my koi has a bump growing on it's side looks like a tumor. I am
wondering if I should quareantine the fish and treat with some kind of
medication. The fishs seem i good health other wise.

Answer
Koi can have tumors which can be made of fluid (cysts), fat, parasites, bacteria (like fish tuberculosis boils), viruses (like carp pox), etc.  What color is the bump?  How big is it?  It may or may not be contagious.  If you haven't added any new fish this year, it's probably not contagious if the other fish don't have it.  At this point, they would be exposed anyway if it were contagious.  If you want to treat the fish, I suggest pond salt, MelaFix, and antibiotics.  Of course, if it's a parasite or virus, those won't help much.  Good luck!

Robyn
fishpondinfo.com