Alan Kirk recommends Fryers Balsam as a carp antiseptic.

This stuff is brilliant for carp and their wounds, just recommending a cheap alternative.....sod all that pay a fiver kryston crap, get this stuff called "Fryers Balsam" and guess where you get it....your local chemist for a quid. Does well and does not effect the carp in any way other than heal some hook and other wounds.