Chaya, I didn't have any mildew but had dark areas on the grout. I tried the hydrogen peroxide and was pleasantly surprised how well it did with little scrubbing.
I also use a product called Stain Solver. It is an oxygen bleach. it won't clean rust stains or hard water deposits but does a great job on grout. It is also environmentally safe product. It can also be used on wood decks although I didn't try that.
I also use a product called Stain Solver. It is an oxygen bleach. it won't clean rust stains or hard water deposits but does a great job on grout. It is also environmentally safe product. It can also be used on wood decks although I didn't try that.