clean mildew off your boat seats be sure to stick in a moisture absorbing, mildew prevention substance. You can buy buckets of commercially produced mildew prevention solution or you can try one of many popular household products. A tin or two of charcoal bricks (not match light!) works very well. You should use a mold and mildew killer and cleaner to stop mildew in its tracks and prevent it from continuing to grow. You can buy these at any gardening store and most marine suppliers.