Unlike many bath mats or dish racks, the Dorai Diomat utilizes rapid drying that dissipates moisture and helps to prevent mold. However mold is a pesky invader, while Dorai's Diomat can hold up to 150% of its weight in water, it needs adequate air flow to rapidly dry. If your Dorai products are constantly saturated and not able to properly dry out, they can eventually grow mold (at a much slower rate than traditional products). To prevent this be sure your products are slightly elevated from the surface (by using the non-slip pad included in the Bath Stone), and let them fully dry out between uses. When overly saturated, prop them up against a wall and when they return to their original light color they are ready to go. Alternatively hit it with a hair dryer to speed up the process :)
Similar to light colored towels or sheets, darker liquids or self tanners can cause some staining if absorbed into the mat. Lighter liquids will not typically stain your mat. In the event that your mat gets stained, it can be cleaned in two ways. For light stains or scuffs, use the included sand paper to gently rub off any marks. For more extreme stains, small amounts of bleach or hydrogen peroxide will do the trick.