T.O.
Anything that you can leave sit on the black spots works. I used Soft Scrub the other day and let it sit for the whole day. I didn't even scrub anything I just rinsed it off. (The black mold was making babies in the shower) LOL It was terrible..and under the caulking. Needless to say the shower has never been whiter and it smells really good. I've also used the Clorox gel toilet bowl cleaner in times of need and it does just fine.