Sorry to say there is no easy way to keep your mat mold free other that to keep it completely dry when not in use.
How to remove mold from bath mat.
Just throw it away and buy another and do this.
To eliminate mold or mildew leave the rubber bath mat in the diluted bleach solution for 3 4 hours.
Turn on a fan exhaust fan or open a window after you take a shower to reduce the level of mildew causing moisture in your bathroom.
Keep your bath mat clean by spraying it with a bathroom cleaner and wiping it down every week.
If you d rather not spend your bathroom cleaning time scrubbing mold and mildew from your bath mat be sure to hang it after each use.
Finally i would give your mat a good soak in vinegar and water at least once every couple months with a good rinse afterward and hang to dry.
You can wash it in the washing machine cold or warm water please and don t put it.
When you get your new one after using the tub remove the rubber mat and roll it in a towel to dry it.
If your bath mat has become a victim of mold and mildew you have several recourses.
We know that you have lots of questions about cleaning and we want to give you those answers.
To freshen up the bath mat with a quick clean scrub the rubber bath mat with a cleaning brush or scouring pad to remove dirt and debris after soaking for a few minutes.
Rubber bath mat mold and mildew removal.
Prevent new mildew stains from forming by hanging up your bath mat in a cool dry area after each use.