Cropping dog ears is done to prevent their ears from looking like your fishes fins.And docking tails had no purpose in fighting dogs.tail docking was highly frowned upon with true dog fighters back in the day.no dog with any heart at all will even be close to a tail! Is trimming fins really any different than piercings fins??I'm again piercing n tattoos on fish by the way. But wouldn't have any problem trimming fins!what if your fish has fin rot on the ends.would you trim then or just add chemicals for treatment??trimming fins isn't any different than me trimming my parrots feathers, or cropping ears, or removing dewclaws, or trimming your pets toenails.