How to spot black mold when it is not visible:
* Look for bloating in tile wall
* Look for black seeping out of grout joints or caulk joints
* Notice if particular areas of the shower will simply not be rid of mold, no matter how many times you bleach it, it keeps coming back
* Knock on Tile to see if it sounds hollow: this is not always an indication of mold.

The best way to rid yourself of this mold, is to tear our all or the portion of shower infected. Allow for area to dry out (this will practically kill the mold by itself). Kill any remaining mold with bleach.

For more questions or for a free estimate on Mold Removal and Shower Installation, check out tilefast.com