[Chuck Gallagher]

I found that 5% distilled white vinegar and 95% water and a scrub brush cleans and stops the mildew.
Also, after scrubbing, don't rinse it off right away to allow the vinegar some time to kill all the mold. About an hour should do.
A gallon of pre-mix can be bought in most grocery stores for under a dollar. Good luck.
Chuck