I like Gerald's formula. Triton-X is the surfactant you want to use (non-ionic and quite hydrophilic). Most people go overboard with wetting agent, I think... The idea isn't to make a bubble bath, but just to reduce water beading on the film.

I'm currently using a wetting agent from Photographer's Formulary. They recommend two drops per roll of film in the tank. At that rate my 125-ml bottle will last forever.