mildew prevention
I agree with all of the prior responses and would add that I've had great success with a product called (surpisingly!) No More Mildew that I ordered from National Alergy Supply www.natlallergy.com. Used it once in the early part of the season and, along with the other suggestions you've received, have not had any mildew. It comes in a spray bottle for around $20 - product number 60-0032B/ Also have used another product called NAS-12 which is a cleaner. From their desciption: "Chlorine bleach products can be harmful with prolonged use. NAS-12's safe, non-toxic, biodegradable, odorless formulation works on shower walls and curtains, grouting, vinyl outdoor furniture, vinyl wallpaper, paint surfaces, boat exteriors, leather...any surface where mold and mildew grow. NAS-12 is pre-mixed, easy to use and contains no chlorine. Spray it on, let it stand for a few minutes, then scrub lightly with a sponge or cloth. Quart bottle comes complete with a sprayer"