I used to clean mine with bleach. Be sure and have it well-ventilated plus a fan. I had the ugly grout guys clean it and re seal. It looked nice for a month. Mold back! ($300.00) Found out the pan had a leak and water was standing in the framing under the shower. We took the whole shower out and had a seamless surface shower installed. Made of Terra stone. No more grout. Also had a swinging shower door installed. No channel to hold water. A lot easier to get in & out. Looks great!