Thanks for adding more helpfull information to my post , fellas .
When I think it's necessary , i.e. the Carp is actually bleeding , I would probably use my Gardner Intensive Care ; the only trouble I find is that I get blue dye all over the place . So for a more targeted application I've bought some Acute Anti-Bacterial Swabs from Carp Care UK .
I haven't used the swabs yet , but the marketing blurb sounds plausable , so I'll find out eventually .