I have had freash water tanks for over thirty years, have had salt for several years, freash water, simply wash withtap water no soap, then after you are finished working on your tank wash with soap and warm water like you normally wash your hands nothing special, generally I don't even thnk about washing my hands before I work on the salt water, because the first thing I usally am doing is cleaning the skimmer cup or washing out the filter pad, those are loaded with fish poo and other nasty stuff, I do make sure I scrub my hands really well with soap and warm/hot water when I finish and I usally use a finger nail brush as well, I don't worry about it too much, but I do not like a bunch of people sticking there hand in my tanks or other peoples kids throwing toys in there,